It is excision of the eyeball. It can be performed under
local anaesthesia in adults and under general
anaesthesia in children.
Indications
1. Absolute indications are retinoblastoma and
malignant melanoma.
2. Relative indications are painful blind eye,
mutilating ocular injuries, anterior staphyloma
and phthisis bulbi.
Surgical techniques (Fig. 11.38).
1. Separation of conjunctiva and Tenon’s capsule
(Fig. 11.38A): Conjunctiva is incised all around
the limbus with the help of spring scissors.
Undermining of the conjunctiva and Tenon’s
capsule is done combinedly, all around up to the
equator, using blunt-tipped curved scissors. This
manoeuvre exposes the extraocular muscles.
2. Separation of extraocular muscles (Fig. 11.38B):
The rectus muscles are pulled out one by one
with the help of a muscle hook and a 3-0 silk
suture is passed near the insertion of each
muscle. The muscle is then cut with the help of
tenotomy scissors leaving behind a small stump
carrying the suture. The inferior and superior
oblique muscles are hooked out and cut near the
globe.
3. Cutting of optic nerve (Fig. 11.38C): The eyeball
is prolapsed out by stretching and pushing down
the eye speculum. The eyeball is pulled out with
the help of sutures passed through the muscle
stumps. The enucleation scissiors is then
introduced along the medial wall up to the
posterior aspect of the eyeball. Optic nerve is felt
and then cut with the scissors while maintaining
a constant pull on the eyeball.
4. Removal of eyeball: The eyeball is pulled out of
the orbit by incising the remaining tissue adherent
to it.
5. Haemostasis is achieved by packing the orbital
cavity with a wet pack and pressing it back.
6. Inserting an orbital implant (Fig. 11.38D):
Preferably an orbital implant (made up of PMMA
Medpor or hydroxyapatite) of appropriate size
should be inserted into the orbit and sutured
with the rectus muscles.
7. Closure of conjunctiva and Tenon’s capsule is
done separately. Tenon’s capsule is sutured
horizontally with 6-0 vicryl or chromic catgut.
Conjunctiva is sutured vertically so that
conjunctival fornies are retained deep with 6-0
silk sutures (Fig. 11.38 E) which are removed after
8-10 days.
8. Dressing. Antibiotic ointment is applied, lids are
closed and dressing is done with firm pressure
using sterile eye pads and a bandage.
Fitting of artifial prosthetic eye
Conforme may be used postoperatively so that the
conjuctival fornices are retained deep. A proper sized
prosthetic eye can be inserted for good cosmetic
appearance (Fig. 11.39) after 6 weeks when healing of
the enucleated socket is complete.
Showing posts with label retina. Show all posts
Showing posts with label retina. Show all posts
Thursday, December 30, 2010
Retinoblastoma
It is a common congenital malignant tumour arising
from the neurosensory retina in one or both eyes.
Incidence
1. It is the most common intraocular tumour of
childhood occurring 1 in 20,000 live births.
2. Age. Though congenital, it is not recognised at
birth, and is usually seen between 1 and 2 years
of age.
3. Sex. There is no sex predisposition.
4. Race. It is rarer in Negroes than Whites.
5. Bilaterality. In 25-30 percent cases, there is
bilateral involvement, although one eye is affected
more extensively and earlier than the other.
Genetics and heredity
Retinoblastoma (RB) gene has been identified as 14
band on the long-arm of chromosome 13 (13q 14) and
is a ‘cancer suppressor’ or ‘antioncogenic’ gene.
Deletion or inactivation of this protective gene by
two mutations (Knudson’s two hit hypothesis) results
in occurrence of retinoblastoma.
Retinoblastoma may arise as hereditary and nonherditary
forms.
1. Hereditary or familial cases. In such cases first
hit (mutation) occurs in one of the parental germ cells
before fertilization. This means mutation will occur in
all somatic cells (predisposing to develop even nonocular
tumour). Second hit (mutation) occurs late in
postzygote phase and affects the second allele,
resulting in development of retinoblastoma. Some
facts about hereditary retinoblastoma are:
Accounts for 40% of all cases.
All bilateral cases and about 15% of the unilateral
cases are hereditary.
Most hereditary cases are multifocal.
Some hereditary cases have trilateral retinoblastoma
(i.e., have associated pinealoblastoma).
Inheritance is autosomal dominant and the risk of
transmitting the gene mutation is 50%. Because
of high peneterance 40% of offspring of a surviver
of heraditary retinoblastoma will develop the
tumour.
There are 40% chances of developing tumour in
a sibling of a child with bilateral retinoblastoma
(with unaffected parents).
2. Non-hereditary or sporadic cases. In nonhereditary
cases both hits (mutations) occur in the
embryo after fertilization and in the same retinal cell.
Some facts about non-hereditary (somatic)
retinoblastoma are:
Accounts for 60% of all cases.
All non-hereditary cases are unilateral and
unifocal and accounts for 85% of the all unilateral
cases of retinoblastoma.
Patient is not predisposed to get second nonocular
cancer.
Tumour is not transmissible.
Clinical picture
It may be divided into four stages:
I. Quiescent stage. It lasts for about 6 months to one
year. During this stage, child may have any of the
following features:
1. Leukocoria or yellowish-white pupillary reflex
(also called as amaurotic cat’s eye appearance)
is the commonest feature noticed in this stage
(Fig. 11.34).
2. Squint, usually convergent, may develop in some
cases.
3. Nystagmus is a rare feature, noticed in bilateral
cases.
4. Defective vision. Very rarely, when the tumour
arises late (3-5 years of age), the child may
complain of defective vision.
5. Ophthalmoscopic features of tumour. In the early
stages, before the appearance of leukocoria,
fundus examination after full mydriasis may reveal
the growth. Ophthalmoscopic signs in two types
of retinoblastoma are as follows:
i. Endophytic retinoblastoma (Fig. 11.35A): It
grows inwards from the retina into the
vitreous cavity. On ophthalmoscopic
examination, the tumour looks like a well
circumscribed polypoidal mass of white or
pearly pink in colour. Fine blood vessels and
sometimes a haemorrhage may be present on
its surface. In the presence of calcification, it
gives the typical ‘cottage cheese’ appearance.
There may be multiple growths projecting
into the vitreous.
ii. Exophytic retinoblastoma (Fig. 11.35B). It
grows outwards and separates the retina
from the choroid. On fundus examination it
gives appearance of exudative retinal
detachment (see page 278).
II. Glaucomatous stage. It develops when
retinoblastoma is left untreated during the quiescent
stage. This stage is characterised by severe pain,
redness, and watering.
Signs. Eyeball is enlarged with apparent proptosis,
conjunctiva is congested, cornea become hazy,
intraocular pressure is raised. Occasionally, picture
simulating severe, acute uveitis usually associated
with pseudohypopyon and/or hyphaema may be the
presenting mode (retinoblastoma masquerading as
iridocyclitis).
III. Stage of extraocular extension. Due to
progressive enlargement, of tumour the globe bursts
through the sclera, usually near the limbus or near
the optic disc. It is followed by rapid fungation and
involvement of extraocular tissues resulting in marked
proptosis (Fig. 11.36).
IV. Stage of distant metastasis. It is characterised by
the involvement of distant structures as follows:
1. Lymphatic spread first occurs in the preauricular
and neighbouring lymph nodes.
2. Direct extension by continuity to the optic nerve
and brain is common.
3. Metastasis by blood stream involves cranial and
other bones. Metastasis in other organs, usually
the liver, is relatively rare.
Differential diagnosis
1. Differential diagnosis of leukocoria. Various
conditions other than retinoblastoma, which present
as leukocoria are collectively called as
‘pseudoglioma'. A few common conditions are
congenital cataract, inflammatory deposits in vitreous
following a plastic cyclitis or choroiditis, coloboma
of the choroid, the retrolental fibroplasia (retinopathy
of prematurity), persistent hyperplastic primary
vitreous, toxocara endophthalmitis and exudative
retinopathy of Coats.
2. Endophytic retinoblastoma discovered on fundus
examination should be differentiated from retinal
tumours in tuberous sclerosis and neurofibromatosis,
astrocytoma and a patch of exudative choroiditis.
3. Exophytic retinoblastoma should be differentiated
from other causes of exudative retinal detachment
(see page 278).
Diagnosis
1. Examination under anaesthesia: It should be
performed in all clinically suspected cases. It
should include fundus examination of both eyes
after full mydriasis with atropine (direct as well as
indirect ophthalmoscopy), measurement of
intraocular pressure and corneal diameter.
2. Plain X-rays of orbit may show calcification
which occurs in 75 percent cases of
retinoblastoma.
3. Lactic dehydrogenase (LDH) level is raised in
aqueous humour.
4. Ultrasonography and CT scanning are very
useful in the diagnosis. CT also demonstrates
extension to optic nerve, orbit and CNS, if any
(Fig. 11.37).
Treatment
1. Tumour destructive therapy. When tumour is
diagnosed at an early stage I i.e., when tumour is
involving less than half of retina and optic nerve is
not involved (usually in the second eye of bilateral
cases), it may be treated conservatively by any one
or more of the following tumour destructive methods
depending upon the size and location of the tumour:
Present recomendations are for sequential
aggressive local therapy (SALT) comprising of multimodality
therapy as below:
Chemoreduction followed by local therapy
(Cryotherapy, thermochemotherapy or brachytherapy)
is recommended for large tumours (>12
mm in diameter)
Radiotherapy (external beam radiotherapy i.e.,
EBRT or brachytherapy) combined with
chemotherapy is recommended for medium size
tumour <12 mm in diameter and <8mm in thickness).
Cryotherapy is indicated for a small tumour (<4.5
mm indiameter and <2.5 mm in thickness) located
anterior to equator.
Laser photocoagulation is used for a small
tumour located posterior to equator <3 mm from
fovea.
Thermotherapy with diode laser is used for a
small tumour located posterior to equator away
from macula.
However, if the above modalities are not available,
the eyeball should be enucleated without hesitation.
2. Enucleation. It is the treatment of choice when:
Tumour involves more than half of the retina.
Optic nerve is involved.
Glaucoma is present and anterior chamber is
involved.
The eyeball should be enucleated along with maximum
length of the optic nerve taking special care not to
perforate the eyeball.
If optic nerve shows invasion, postoperative
treatment should include:
Radiotherapy (5000 rads) should be applied to
the orbital apex.
Chemotherapy, consisting of vincristine,
carboplatin, and etoposide which may be
combined with cyclosporin should be
supplemented.
3. Palliative therapy is given in following cases
where prognosis for life is dismal in spite of aggressive
treatment:
Retinoblastoma with orbital extension,
Retinoblastoma with intracranial extension, and
Retinoblastoma with distant metastasis.
Palliative therapy should include combination of :
Chemotherapy,
Surgical debulking of the orbit or orbital
exentration, and
External beam radiotherapy (EBRT)
Note: Exentration of the orbit (a mutilating surgery
commonly performed in the past) is now not preferred
by many surgeons.
Prognosis
1. If untreated the prognosis is almost always bad
and the patient invariably dies. Rarely
spontaneous regression with resultant cure and
shrinkage of the eyeball may occur due to necrosis
followed by calcification; suggesting role of some
immunological phenomenon.
2. Prognosis is fair (survival rate 70-85%) if the
eyeball is enucleated before the occurrence of
extraocular extension.
3. Poor prognostic factors are: Optic nerve
involvement, undifferentiated tumour cells and
massive choroidal invasion.
from the neurosensory retina in one or both eyes.
Incidence
1. It is the most common intraocular tumour of
childhood occurring 1 in 20,000 live births.
2. Age. Though congenital, it is not recognised at
birth, and is usually seen between 1 and 2 years
of age.
3. Sex. There is no sex predisposition.
4. Race. It is rarer in Negroes than Whites.
5. Bilaterality. In 25-30 percent cases, there is
bilateral involvement, although one eye is affected
more extensively and earlier than the other.
Genetics and heredity
Retinoblastoma (RB) gene has been identified as 14
band on the long-arm of chromosome 13 (13q 14) and
is a ‘cancer suppressor’ or ‘antioncogenic’ gene.
Deletion or inactivation of this protective gene by
two mutations (Knudson’s two hit hypothesis) results
in occurrence of retinoblastoma.
Retinoblastoma may arise as hereditary and nonherditary
forms.
1. Hereditary or familial cases. In such cases first
hit (mutation) occurs in one of the parental germ cells
before fertilization. This means mutation will occur in
all somatic cells (predisposing to develop even nonocular
tumour). Second hit (mutation) occurs late in
postzygote phase and affects the second allele,
resulting in development of retinoblastoma. Some
facts about hereditary retinoblastoma are:
Accounts for 40% of all cases.
All bilateral cases and about 15% of the unilateral
cases are hereditary.
Most hereditary cases are multifocal.
Some hereditary cases have trilateral retinoblastoma
(i.e., have associated pinealoblastoma).
Inheritance is autosomal dominant and the risk of
transmitting the gene mutation is 50%. Because
of high peneterance 40% of offspring of a surviver
of heraditary retinoblastoma will develop the
tumour.
There are 40% chances of developing tumour in
a sibling of a child with bilateral retinoblastoma
(with unaffected parents).
2. Non-hereditary or sporadic cases. In nonhereditary
cases both hits (mutations) occur in the
embryo after fertilization and in the same retinal cell.
Some facts about non-hereditary (somatic)
retinoblastoma are:
Accounts for 60% of all cases.
All non-hereditary cases are unilateral and
unifocal and accounts for 85% of the all unilateral
cases of retinoblastoma.
Patient is not predisposed to get second nonocular
cancer.
Tumour is not transmissible.
Clinical picture
It may be divided into four stages:
I. Quiescent stage. It lasts for about 6 months to one
year. During this stage, child may have any of the
following features:
1. Leukocoria or yellowish-white pupillary reflex
(also called as amaurotic cat’s eye appearance)
is the commonest feature noticed in this stage
(Fig. 11.34).
2. Squint, usually convergent, may develop in some
cases.
3. Nystagmus is a rare feature, noticed in bilateral
cases.
4. Defective vision. Very rarely, when the tumour
arises late (3-5 years of age), the child may
complain of defective vision.
5. Ophthalmoscopic features of tumour. In the early
stages, before the appearance of leukocoria,
fundus examination after full mydriasis may reveal
the growth. Ophthalmoscopic signs in two types
of retinoblastoma are as follows:
i. Endophytic retinoblastoma (Fig. 11.35A): It
grows inwards from the retina into the
vitreous cavity. On ophthalmoscopic
examination, the tumour looks like a well
circumscribed polypoidal mass of white or
pearly pink in colour. Fine blood vessels and
sometimes a haemorrhage may be present on
its surface. In the presence of calcification, it
gives the typical ‘cottage cheese’ appearance.
There may be multiple growths projecting
into the vitreous.
ii. Exophytic retinoblastoma (Fig. 11.35B). It
grows outwards and separates the retina
from the choroid. On fundus examination it
gives appearance of exudative retinal
detachment (see page 278).
II. Glaucomatous stage. It develops when
retinoblastoma is left untreated during the quiescent
stage. This stage is characterised by severe pain,
redness, and watering.
Signs. Eyeball is enlarged with apparent proptosis,
conjunctiva is congested, cornea become hazy,
intraocular pressure is raised. Occasionally, picture
simulating severe, acute uveitis usually associated
with pseudohypopyon and/or hyphaema may be the
presenting mode (retinoblastoma masquerading as
iridocyclitis).
III. Stage of extraocular extension. Due to
progressive enlargement, of tumour the globe bursts
through the sclera, usually near the limbus or near
the optic disc. It is followed by rapid fungation and
involvement of extraocular tissues resulting in marked
proptosis (Fig. 11.36).
IV. Stage of distant metastasis. It is characterised by
the involvement of distant structures as follows:
1. Lymphatic spread first occurs in the preauricular
and neighbouring lymph nodes.
2. Direct extension by continuity to the optic nerve
and brain is common.
3. Metastasis by blood stream involves cranial and
other bones. Metastasis in other organs, usually
the liver, is relatively rare.
Differential diagnosis
1. Differential diagnosis of leukocoria. Various
conditions other than retinoblastoma, which present
as leukocoria are collectively called as
‘pseudoglioma'. A few common conditions are
congenital cataract, inflammatory deposits in vitreous
following a plastic cyclitis or choroiditis, coloboma
of the choroid, the retrolental fibroplasia (retinopathy
of prematurity), persistent hyperplastic primary
vitreous, toxocara endophthalmitis and exudative
retinopathy of Coats.
2. Endophytic retinoblastoma discovered on fundus
examination should be differentiated from retinal
tumours in tuberous sclerosis and neurofibromatosis,
astrocytoma and a patch of exudative choroiditis.
3. Exophytic retinoblastoma should be differentiated
from other causes of exudative retinal detachment
(see page 278).
Diagnosis
1. Examination under anaesthesia: It should be
performed in all clinically suspected cases. It
should include fundus examination of both eyes
after full mydriasis with atropine (direct as well as
indirect ophthalmoscopy), measurement of
intraocular pressure and corneal diameter.
2. Plain X-rays of orbit may show calcification
which occurs in 75 percent cases of
retinoblastoma.
3. Lactic dehydrogenase (LDH) level is raised in
aqueous humour.
4. Ultrasonography and CT scanning are very
useful in the diagnosis. CT also demonstrates
extension to optic nerve, orbit and CNS, if any
(Fig. 11.37).
Treatment
1. Tumour destructive therapy. When tumour is
diagnosed at an early stage I i.e., when tumour is
involving less than half of retina and optic nerve is
not involved (usually in the second eye of bilateral
cases), it may be treated conservatively by any one
or more of the following tumour destructive methods
depending upon the size and location of the tumour:
Present recomendations are for sequential
aggressive local therapy (SALT) comprising of multimodality
therapy as below:
Chemoreduction followed by local therapy
(Cryotherapy, thermochemotherapy or brachytherapy)
is recommended for large tumours (>12
mm in diameter)
Radiotherapy (external beam radiotherapy i.e.,
EBRT or brachytherapy) combined with
chemotherapy is recommended for medium size
tumour <12 mm in diameter and <8mm in thickness).
Cryotherapy is indicated for a small tumour (<4.5
mm indiameter and <2.5 mm in thickness) located
anterior to equator.
Laser photocoagulation is used for a small
tumour located posterior to equator <3 mm from
fovea.
Thermotherapy with diode laser is used for a
small tumour located posterior to equator away
from macula.
However, if the above modalities are not available,
the eyeball should be enucleated without hesitation.
2. Enucleation. It is the treatment of choice when:
Tumour involves more than half of the retina.
Optic nerve is involved.
Glaucoma is present and anterior chamber is
involved.
The eyeball should be enucleated along with maximum
length of the optic nerve taking special care not to
perforate the eyeball.
If optic nerve shows invasion, postoperative
treatment should include:
Radiotherapy (5000 rads) should be applied to
the orbital apex.
Chemotherapy, consisting of vincristine,
carboplatin, and etoposide which may be
combined with cyclosporin should be
supplemented.
3. Palliative therapy is given in following cases
where prognosis for life is dismal in spite of aggressive
treatment:
Retinoblastoma with orbital extension,
Retinoblastoma with intracranial extension, and
Retinoblastoma with distant metastasis.
Palliative therapy should include combination of :
Chemotherapy,
Surgical debulking of the orbit or orbital
exentration, and
External beam radiotherapy (EBRT)
Note: Exentration of the orbit (a mutilating surgery
commonly performed in the past) is now not preferred
by many surgeons.
Prognosis
1. If untreated the prognosis is almost always bad
and the patient invariably dies. Rarely
spontaneous regression with resultant cure and
shrinkage of the eyeball may occur due to necrosis
followed by calcification; suggesting role of some
immunological phenomenon.
2. Prognosis is fair (survival rate 70-85%) if the
eyeball is enucleated before the occurrence of
extraocular extension.
3. Poor prognostic factors are: Optic nerve
involvement, undifferentiated tumour cells and
massive choroidal invasion.
CYSTOID MACULAR EDEMA (CME)
It refers to collection of fluid in the outer plexiform
(Henle’s layer) and inner nuclear layer of the retina,
centred around the foveola.
Etiology
It is associated with a number of disorders. A few
common causes are as follows:
1. As postoperative complication following cataract
extraction and penetrating keratoplasty.
2. Retinal vascular disorders e.g., diabetic
retinopathy and central retinal vein occlusion.
3. Intraocular inflammations e.g., pars planitis,
posterior uveitis, Behcet disease.
4. As a side-effect of drugs e.g., following use of
adrenaline eyedrops, especially for aphakic
glaucoma.
5. Retinal dystrophies e.g., retinitis pigmentosa.
Pathogenesis
CME develops due to leakage of fluid following
breakdown of inner blood-retinal barrier (i.e., leakage
from the retinal capillaries).
Clinical features
1. Visual loss. Initially there is minimal to moderate
loss of vision, unassociated with other symptoms.
If oedema persists, there may occur permanent
decrease in vision.
2. Ophthalmoscopy in clinically established cases
reveals a typical ‘Honey-comb appearance’ of
macula (due to multiple cystoid oval spaces) (Fig.
11.24). CME is best examined with a fundus
contact lens on slit-lamp or +90D lens.
3. Fundus fluorescein angiography demonstrates
leakage and accumulation of dye in the macular
region which in a well-established case presents
a ‘flower petal appearance’ (Fig. 11.25).
Complications
Long-standing CME may end in lamellar macular hole.
Treatment
1. Treatment of the causative factor, e.g.,
photocoagulation for diabetic CSME; cessation of
causative topical 2% adrenaline eye drops, so on.
2. Topical antiprostaglandin drops like
indomethacin or flurbiprofen, used pre and postoperatively,
prevent the occurrence of CME
associated with intraocular surgery.
3. Topical and systemic steroids may be of some
use in established cases.
4. Systemic carbonic anhydrase inhibitors (CAIs)
e.g., oral acetazolamide may be beneficial is some
cases of CME
(Henle’s layer) and inner nuclear layer of the retina,
centred around the foveola.
Etiology
It is associated with a number of disorders. A few
common causes are as follows:
1. As postoperative complication following cataract
extraction and penetrating keratoplasty.
2. Retinal vascular disorders e.g., diabetic
retinopathy and central retinal vein occlusion.
3. Intraocular inflammations e.g., pars planitis,
posterior uveitis, Behcet disease.
4. As a side-effect of drugs e.g., following use of
adrenaline eyedrops, especially for aphakic
glaucoma.
5. Retinal dystrophies e.g., retinitis pigmentosa.
Pathogenesis
CME develops due to leakage of fluid following
breakdown of inner blood-retinal barrier (i.e., leakage
from the retinal capillaries).
Clinical features
1. Visual loss. Initially there is minimal to moderate
loss of vision, unassociated with other symptoms.
If oedema persists, there may occur permanent
decrease in vision.
2. Ophthalmoscopy in clinically established cases
reveals a typical ‘Honey-comb appearance’ of
macula (due to multiple cystoid oval spaces) (Fig.
11.24). CME is best examined with a fundus
contact lens on slit-lamp or +90D lens.
3. Fundus fluorescein angiography demonstrates
leakage and accumulation of dye in the macular
region which in a well-established case presents
a ‘flower petal appearance’ (Fig. 11.25).
Complications
Long-standing CME may end in lamellar macular hole.
Treatment
1. Treatment of the causative factor, e.g.,
photocoagulation for diabetic CSME; cessation of
causative topical 2% adrenaline eye drops, so on.
2. Topical antiprostaglandin drops like
indomethacin or flurbiprofen, used pre and postoperatively,
prevent the occurrence of CME
associated with intraocular surgery.
3. Topical and systemic steroids may be of some
use in established cases.
4. Systemic carbonic anhydrase inhibitors (CAIs)
e.g., oral acetazolamide may be beneficial is some
cases of CME
RETINITIS PIGMENTOSA
This primary pigmentary retinal dystrophy is a
hereditary disorder predominantly affecting the rods
more than the cones.
Inheritance
Most common mode is autosomal recessive, followed
by autosomal dominant. X-linked recessive is the least
common.
Incidence
It occurs in 5 persons per 1000 of the world
population.
Age. It appears in the childhood and progresses
slowly, often resulting in blindness in advanced
middle age.
Race. No race is known to be exempt or prone to it.
Sex. Males are more commonly affected than
females in a ratio of 3:2.
Laterality. Disease is almost invariably bilateral
and both the eyes are equally affected.
Clinical features
(A) Visual symptoms
1. Night blindness. It is the characteristic feature
and may present several years before the visible
changes in the retina appear. It occurs due to
degeneration of the rods.
2. Dark adaptation. Light threshold of the peripheral
retina is increased; though the process of dark
adaptation itself is not affected until very late.
3. Tubular vision occurs in advanced cases.
(B) Fundus changes (Fig. 11.18)
1. Retinal pigmentary changes. These are typically
perivascular and resemble bone corpuscles in
shape. Initially, these changes are found in the
equatorial region only and later spread both
anteriorly and posteriorly.
2. Retinal arterioles are attenuated (narrowed) and
may become thread-like in late stages.
3. Optic disc becomes pale and waxy in later stages
and ultimately consecutive optic atrophy occurs
(Fig. 11.19).
4. Other associated changes which may be seen are
colloid bodies, choroidal sclerosis, cystoid macular
oedema, atrophic or cellophane maculopathy.
(C) Visual field changes (Fig. 11.20)
Annular or ring-shaped scotoma is a typical feature
which corresponds to the degenerated equatorial zone
of retina. As the disease progresses, scotoma
increases anteriorly and posteriorly and ultimately only central vision is left (tubular vision). Eventually
even this is also lost and the patient becomes blind.
(D) Electrophysiological changes
Typical electrophysiological changes appear early in
the disease before the subjective symptoms or the
objective signs (fundus changes) appear.
1. Electro-retinogram (ERG) is subnormal or
abolished.
2. Electro-oculogram (EOG) shows absence of light
peak.
Associations of retinitis pigmentosa
I. Ocular associations. These include myopia, primary
open angle glaucoma, microphthalmos, conical cornea
and posterior subcapsular cataract.
II. Systemic associations. These are in the form of
following syndromes:
1. Laurence-Moon-Biedl syndrome. It is
characterised by retinitis pigmentosa, obesity,
hypogenitalism, polydactyly and mental
deficiency.
2. Cockayne’s syndrome. It comprises retinitis
pigmentosa, progressive infantile deafness,
dwarfism, mental retardation, nystagmus and
ataxia.
3. Refsum’s syndrome. It is characterised by retinitis
pigmentosa, peripheral neuropathy and cerebellar
ataxia.
4. Usher’s syndrome. It includes retinitis pigmentosa
and labyrinthine deafness.
5. Hallgren’s syndrome. It comprises retinitis
pigmentosa, vestibulo-cerebellar ataxia, congenital
deafness and mental deficiency.
Atypical forms of retinitis pigmentosa
1. Retinitis pigmentosa sine pigmento. It is
characterised by all the clinical features of typical
retinitis pigmentosa, except that there are no
visible pigmentary changes in the fundus.
2. Sectorial retinitis pigmentosa. It is characterised
by involvement of only one sector of the retina.
3. Pericentric retinitis pigmentosa. In this condition
all the clinical features are similar to typical retinitis
pigmentosa except that pigmentary changes are
confined to an area, immediately around the
macula.
4. Retinitis punctata albescens. It is characterised
by the presence of innumerable discrete white
dots scattered over the fundus without pigmentary
changes. Other features are narrowing of
arterioles, night blindness and constriction of
visual fields.
Treatment
It is most unsatisfactory; rather we can say that till
date there is no effective treatment for the disease.
1. Measures to stop progression, which have been
tried from time to time, without any breakthrough
include: vasodilators, placental extracts,
transplantation of rectus muscles into
suprachoroidal space, light exclusion therapy,
ultrasonic therapy and acupuncture therapy.
Recently vitamin A and E have been
recommended to check its progression.
2. Low vision aids (LVA) in the form of ‘magnifying
glasses’ and ‘night vision device’ may be of
some help.
3. Rehabilitation of the patient should be carried
out as per his socio-economic background.
4. Prophylaxis. Genetic counselling for no
consanguinous marriages may help to reduce the
incidence of disease. Further, affected individuals
should be advised not to produce children.
hereditary disorder predominantly affecting the rods
more than the cones.
Inheritance
Most common mode is autosomal recessive, followed
by autosomal dominant. X-linked recessive is the least
common.
Incidence
It occurs in 5 persons per 1000 of the world
population.
Age. It appears in the childhood and progresses
slowly, often resulting in blindness in advanced
middle age.
Race. No race is known to be exempt or prone to it.
Sex. Males are more commonly affected than
females in a ratio of 3:2.
Laterality. Disease is almost invariably bilateral
and both the eyes are equally affected.
Clinical features
(A) Visual symptoms
1. Night blindness. It is the characteristic feature
and may present several years before the visible
changes in the retina appear. It occurs due to
degeneration of the rods.
2. Dark adaptation. Light threshold of the peripheral
retina is increased; though the process of dark
adaptation itself is not affected until very late.
3. Tubular vision occurs in advanced cases.
(B) Fundus changes (Fig. 11.18)
1. Retinal pigmentary changes. These are typically
perivascular and resemble bone corpuscles in
shape. Initially, these changes are found in the
equatorial region only and later spread both
anteriorly and posteriorly.
2. Retinal arterioles are attenuated (narrowed) and
may become thread-like in late stages.
3. Optic disc becomes pale and waxy in later stages
and ultimately consecutive optic atrophy occurs
(Fig. 11.19).
4. Other associated changes which may be seen are
colloid bodies, choroidal sclerosis, cystoid macular
oedema, atrophic or cellophane maculopathy.
(C) Visual field changes (Fig. 11.20)
Annular or ring-shaped scotoma is a typical feature
which corresponds to the degenerated equatorial zone
of retina. As the disease progresses, scotoma
increases anteriorly and posteriorly and ultimately only central vision is left (tubular vision). Eventually
even this is also lost and the patient becomes blind.
(D) Electrophysiological changes
Typical electrophysiological changes appear early in
the disease before the subjective symptoms or the
objective signs (fundus changes) appear.
1. Electro-retinogram (ERG) is subnormal or
abolished.
2. Electro-oculogram (EOG) shows absence of light
peak.
Associations of retinitis pigmentosa
I. Ocular associations. These include myopia, primary
open angle glaucoma, microphthalmos, conical cornea
and posterior subcapsular cataract.
II. Systemic associations. These are in the form of
following syndromes:
1. Laurence-Moon-Biedl syndrome. It is
characterised by retinitis pigmentosa, obesity,
hypogenitalism, polydactyly and mental
deficiency.
2. Cockayne’s syndrome. It comprises retinitis
pigmentosa, progressive infantile deafness,
dwarfism, mental retardation, nystagmus and
ataxia.
3. Refsum’s syndrome. It is characterised by retinitis
pigmentosa, peripheral neuropathy and cerebellar
ataxia.
4. Usher’s syndrome. It includes retinitis pigmentosa
and labyrinthine deafness.
5. Hallgren’s syndrome. It comprises retinitis
pigmentosa, vestibulo-cerebellar ataxia, congenital
deafness and mental deficiency.
Atypical forms of retinitis pigmentosa
1. Retinitis pigmentosa sine pigmento. It is
characterised by all the clinical features of typical
retinitis pigmentosa, except that there are no
visible pigmentary changes in the fundus.
2. Sectorial retinitis pigmentosa. It is characterised
by involvement of only one sector of the retina.
3. Pericentric retinitis pigmentosa. In this condition
all the clinical features are similar to typical retinitis
pigmentosa except that pigmentary changes are
confined to an area, immediately around the
macula.
4. Retinitis punctata albescens. It is characterised
by the presence of innumerable discrete white
dots scattered over the fundus without pigmentary
changes. Other features are narrowing of
arterioles, night blindness and constriction of
visual fields.
Treatment
It is most unsatisfactory; rather we can say that till
date there is no effective treatment for the disease.
1. Measures to stop progression, which have been
tried from time to time, without any breakthrough
include: vasodilators, placental extracts,
transplantation of rectus muscles into
suprachoroidal space, light exclusion therapy,
ultrasonic therapy and acupuncture therapy.
Recently vitamin A and E have been
recommended to check its progression.
2. Low vision aids (LVA) in the form of ‘magnifying
glasses’ and ‘night vision device’ may be of
some help.
3. Rehabilitation of the patient should be carried
out as per his socio-economic background.
4. Prophylaxis. Genetic counselling for no
consanguinous marriages may help to reduce the
incidence of disease. Further, affected individuals
should be advised not to produce children.
CENTRAL SEROUS RETINOPATHY (CSR)
Central serous retinopathy (CSR) is characterised by
spontaneous serous detachment of neurosensory
retina in the macular region, with or without retinal
pigment epithelium detachment. Presently it is termed
as idiopathic central serous choroidopathy (ICSC).
Etispathogenesis
It is not known exactly. The condition typically affects
males between 20 and 40 years of age. It is now
believed that an increase in choroidal
hyperpermeability causes a breach in the outer blood
retinal barrier (a small opening or blow out of RPE).
Leakage of fluid across this area results in
development of localized serous detachment of
neurosensory retina. What triggers the choroidal
hyperpermeability is poorly understood. It is being
suggested that an imbalance between the sympathetic
parasympathetic drive that maintains autoregulation
within the choroidal vasculature may be defective in
patients with CSR. Factors reported to induce or
aggravate CSR include: emotional stress,
hypertension, and administration of systemic steroids.
Clinical features
Symptoms. Patient presents with a sudden onset of
painless loss of vision (6/9-6/24) associated with
relative positive scotoma, micropsia and
metamorphopsia.
Ophthalmoscopic examination reveals, mild
elevation of macular area, demarcated by a circular
ring-reflex. Foveal reflex is absent or distorted
(Fig. 11.22).
CSR is usually self-limiting but often recurrent.
Resolution may take three weeks to one year
and often leaves behind small areas of atrophy
and pigmentary disturbances.
Fundus fluorescein angiography helps in confirming
the diagnosis. Two patterns are seen:
Ink-blot pattern. It consists of small hyperfluorescent
spot which gradually increases in size
(Fig. 11.23A).
Smoke-stack pattern. It consists of a small
hyperfluorescent spot which ascends vertically
like a smoke-stack and gradually spreads laterally
to take a mushroom or umbrella configuration
(Fig. 11.23B).
Treatment
1. Reassurance is the only treatment required in
majority of the cases, since CSR undergoes
spontaneous resolution in 80 to 90 percent cases.
Visual acuity returns to normal or near normal
within 4 to 12 weeks.
2. Laser photocoagulation is indicated in following
cases:
Long-standing cases (more than 4 months)
with marked loss of vision.
Patients having recurrent CSR with visual loss.
Patients having permanent loss of vision in
the other eye due to this condition
spontaneous serous detachment of neurosensory
retina in the macular region, with or without retinal
pigment epithelium detachment. Presently it is termed
as idiopathic central serous choroidopathy (ICSC).
Etispathogenesis
It is not known exactly. The condition typically affects
males between 20 and 40 years of age. It is now
believed that an increase in choroidal
hyperpermeability causes a breach in the outer blood
retinal barrier (a small opening or blow out of RPE).
Leakage of fluid across this area results in
development of localized serous detachment of
neurosensory retina. What triggers the choroidal
hyperpermeability is poorly understood. It is being
suggested that an imbalance between the sympathetic
parasympathetic drive that maintains autoregulation
within the choroidal vasculature may be defective in
patients with CSR. Factors reported to induce or
aggravate CSR include: emotional stress,
hypertension, and administration of systemic steroids.
Clinical features
Symptoms. Patient presents with a sudden onset of
painless loss of vision (6/9-6/24) associated with
relative positive scotoma, micropsia and
metamorphopsia.
Ophthalmoscopic examination reveals, mild
elevation of macular area, demarcated by a circular
ring-reflex. Foveal reflex is absent or distorted
(Fig. 11.22).
CSR is usually self-limiting but often recurrent.
Resolution may take three weeks to one year
and often leaves behind small areas of atrophy
and pigmentary disturbances.
Fundus fluorescein angiography helps in confirming
the diagnosis. Two patterns are seen:
Ink-blot pattern. It consists of small hyperfluorescent
spot which gradually increases in size
(Fig. 11.23A).
Smoke-stack pattern. It consists of a small
hyperfluorescent spot which ascends vertically
like a smoke-stack and gradually spreads laterally
to take a mushroom or umbrella configuration
(Fig. 11.23B).
Treatment
1. Reassurance is the only treatment required in
majority of the cases, since CSR undergoes
spontaneous resolution in 80 to 90 percent cases.
Visual acuity returns to normal or near normal
within 4 to 12 weeks.
2. Laser photocoagulation is indicated in following
cases:
Long-standing cases (more than 4 months)
with marked loss of vision.
Patients having recurrent CSR with visual loss.
Patients having permanent loss of vision in
the other eye due to this condition
DIABETIC RETINOPATHY
It refers to retinal changes seen in patients with
diabetes mellitus. With increase in the life expectancy
of diabetics, the incidence of diabetic retinopathy (DR)
has increased. In Western countries, it is the leading
cause of blindness.
Etiopathogenesis
Risk factors associated with occurence of DR are:
1. Duration of diabetes is the most important
determining factor. Roughly 50 percent of patients
develop DR after 10 years, 70 percent after 20
years and 90 percent after 30 years of onset of
the disease.
2. Sex. Incidence is more in females than males (4:3).
3. Poor metabolic control is less important than
duration, but is nevertheless relevant to the
development and progression of DR.
4. Heredity. It is transmitted as a recessive trait
without sex linkage. The effect of heredity is
more on the proliferative retinopathy.
5. Pregnancy may accelerate the changes of diabetic
retinopathy.
6. Hypertension, when associated, may also
accentuate the changes of diabetic retinopathy.
7. Other risk factors include smoking, obesity and
hyperlipidemia.
Classification
Diabetic retinopathy has been variously classified.
Presently followed classification is as follows:
I. Non-proliferative diabetic retinopathy (NPDR)
Mild NPDR
Moderate NPDR
Severe NPDR
Very severe NPDR
II. Proliferative diabetic retinopathy (PDR)
III. Diabetic maculopathy
IV. Advanced diabetic eye disease (ADED)
I. Non-proliferative diabetic retinopathy (NPDR)
Ophthalmoscopic features of NPDR include:
Microaneurysms in the macular area (the earliest
detectable lesion).
Retinal haemorrhages both deep (dot and blot
haemorrhages) and superficial haemorrhages
(flame-shaped). Hard exudates-yellowish-white waxy-looking
patches are arranged in clumps or in circinate
pattern. These are commonly seen in the macular
area.
Retinal oedema characterized by retinal
thickening.
Cotton-wool spots (if > 8, there is high risk of
developing PDR).
Venous abnormalities, beading, looping and
dilatation.
Intraretinal microvascular abnormalities
(IRMA).
Dark-blot haemorrhages representing haemorrhagic
retinal infarcts.
On the basis of severity of the above findings the
NPDR has been further classified as under:
1. Mild NPDR (Fig. 11.14A).
At least one microaneurysm or intraretinal
hemorrhage.
Hard/soft exudates may or may not be present.
2. Moderate NPDR (Fig. 11.14B)
Moderate microaneurysms/intraretinal hemorrhage.
Early mild IRMA.
Hard/soft exudates may or may not present.
3. Severe NPDR. Any one of the following (4-2-1
Rule) (Fig. 11.14C):
Four quadrants of severe microaneurysms/
intraretinal hemorrhages.
Two quadrants of venous beading.
One quadrant of IRMA changes.
4. Very severe NPDR. Any two of the following
(4-2-1 Rule) (Fig. 11.14D):
Four quadrants of severe microaneurysms/
intraretinal hemorrhages.
Two quadrants of venous beading.
One quadrant of IRMA changes.
II. Proliferative diabetic retinopathy (PDR)
Proliferative diabetic retinopathy (Figs. 11.14 E&F)
develops in more than 50 percent of cases after about
25 years of the onset of disease. Therefore, it is more
common in patients with juvenile onset diabetes. The
hallmark of PDR is the occurrence of
neovascularisation over the changes of very severe
non-proliferative diabetic retinopathy. It is
characterised by proliferation of new vessels from
the capillaries, in the form of neovascularisation at
the optic disc (NVD) and/or elsewhere (NVE) in the
fundus, usually along the course of the major temporal
retinal vessels. These new vessels may proliferate in
the plane of retina or spread into the vitreous as
vascular fronds. Later on condensation of connective
tissue around the new vessels results in formation of
fibrovascular epiretinal membrane. Vitreous
detachment and vitreous haemorrhage may occur in
this stage.
Types. On the basis of high risk characteristics
(HRCs) described by diabetic retinopathy study
(DRS) group, the PDR can be further classified as
below:
1. PDR without HRCs (Early PDR) (Fig. 11.14E), and
2. PDR with HRCs (Advanced PDR). High risk
characteristics (HRC) of PDR are as follows
(Fig. 11.14F):
NVD 1/4 to 1/3 of disc area with or without
vitreous haemorrhage (VH) or pre-retinal
haemorrhage (PRH)
NVD < 1/4 disc area with VH or PRH
NVE > 1/2 disc area with VH or PRH
III. Diabetic maculopathy
Changes in macular region need special mention, due
to their effect on vision. These changes may be associated with non-proliferative diabetic
retinopathy (NPDR) or proliferative diabetic
retinopathy (PDR). The diabetic macular edema occurs
due to increased permeability of the retinal capillaries.
It is termed as clinically significant macular edema
(CSME) if one of the following three criteria are
present on slit-lamp examination with 90D lens:
Thickening of the retina at or within 500 micron
of the centre of the fovea.
Hard exudate at or within 500 micron of the centre
of fovea associated with adjacent retinal
thickening.
Development of a zone of retinal thickening one
disc diameter or larger in size, at least a part of
which is within one disc diameter of the foveal
centre.
Clinico-angiographically diabetic maculopathy can be
classified into four types:
1. Focal exudative maculopathy (Fig. 11.14G). It is
characterised by microaneurysms, haemorrhages,
macular oedema and hard exudates which are usually
arranged in a circinate pattern. Fluorescein
angiography reveals focal leakage with adequate
macular perfusion.
2. Diffuse exudative maculopathy. It is characterised
by diffuse retinal oedema and thickening throughout
the posterior pole, with relatively few hard exudates.
Fluorescein angiography reveals diffuse leakage at
the posterior pole.
3. Ischaemic maculopathy. It occurs due to
microvascular blockage. Clinically it is characterised
by marked visual loss with microaneurysms,
haemorrhages, mild or no macular oedema and a few
hard exudates. Fluorescein angiography shows areas
of non-perfusion which in early cases are in the form
of enlargement of foveal avascular zone (FAZ), later
on areas of capillary dropouts are seen and in
advanced cases precapillary arterioles are blocked.
4. Mixed maculopathy. In it combined features of
ischaemic and exudative maculopathy are present.
IV. Advanced diabetic eye disease
It is the end result of uncontrolled proliferative
diabetic retinopathy. It is marked by complications
such as:
Persistent vitreous haemorrhage,
Tractional retinal detachment and
Neovascular glaucoma.
Investigations
Urine examination,
Blood sugar estimation.
Fundus fluorescein angiography should be carried
out to elucidate areas of neovascularisation,
leakage and capillary nonperfusion.
Management
I. Screening for diabetic retinopathy. To prevent
visual loss occurring from diabetic retinopathy a
periodic follow-up is very important for a timely
intervention. The recommendations for periodic
fundus examination are as follows:
Every year, till there is no diabetic retinopathy or
there is mild NPDR.
Every 6 months, in moderate NPDR.
Every 3 months, in severe NPDR.
Every 2 months, in PDR with no high risk
characteristic.
II. Medical treatment. Besides laser and surgery to
the eyes (as indicated and described below), the
medical treatment also plays an essential role. Medical
treatment for diabetic retinopathy can be discussed
as:
1. Control of systemic risk factors is known to
influence the occurrence, progression and effect
of laser treatment on DR. The systemic risk factors
which need attention are.
Strict metabolic control of blood sugar,
Lipid reduction,
Control of associated anaemia, and
Control of associated hypoproteinemia
2. Role of pharmacological modulation. Pharmacological
inhibition of certain biochemical
pathways involved in the pathogenesis of retinal
changes in diabetes is being evaluated These
include:
Protein kinase C (PKC) inhbitors,
Vascular endothelial growth factors (VEGF)
inhibitors,
Aldose reductase and ACE inhibitors, and
Antioxidants such as vitamin E
3. Role of intravitreal steroids in reducing diabetic
macular oedema is also being stressed recently
by following modes of administration:
Flucinolone acetonide intravitreal implant and
Intravitreal injection of triamcinolone
(2 to 4 mg)
III. Photocoagulation. It remains the mainstay in the
treatment of diabetic retinopathy and maculopathy.
Either argon or diode laser can be used. The protocol
of laser application is different for macula and rest of
the retina as follows (Fig. 11.15):
i. Macular photocoagulation. Macula is treated
by laser only if there is clinically significant
macular oedema (CSME). Laser treatment is
contraindicated in ischaemic diabetic maculopathy.
In patients with PDR associated with CSME,
macular photo-coagulation should be considered
first i.e., before PRP since the latter may worsen
macular oedema. Macular photocoagulation
includes two techniques:
Focal treatment (Fig. 11.15A) with argon laser
is carried out for all lesions (microaneurysms,
IRMA or short capillary segments) 500-3000
microns from the centre of the macula, believed
to be leaking and causing CSME. Spot size of
100-200 μm of 0.1 second duration is used.
Grid treatment. Grid pattern laser burns are
applied in the macular area for diffuse diabetic
macular oedema (Fig. 11.15B).
ii. Panretinal photocoagulation (PRP) or scatter
laser consists of 1200-1600 spots, each 500 μm in
size and 0.1 sec. duration. Laser burns are applied
2-3 disc areas from the centre of the macula
extending peripherally to the equator (Fig. 11.15C).
In PRP temporal quadrant of retina is first
coagulated. PRP produces destruction of
ischaemic retina which is responsible for the
production of vasoformative factors.
Indications for PRP are:
PDR with HRCs,
Neovascularization of iris (NVI),
Severe NPDR associated with:
– Poor compliance for follow up,
– Before cataract surgery/YAG capsulotomy,
– Renal failure,
– One-eyed patient, and
– Pregnancy
IV. Surgical treatment. It is required in advanced
cases of PDR. Pars plana vitrectomy is indicated for
dense persistent vitreous haemorrhage, tractional
retinal detachment, and epiretinal membranes.
Associated retinal detachment also needs surgical
repair.
diabetes mellitus. With increase in the life expectancy
of diabetics, the incidence of diabetic retinopathy (DR)
has increased. In Western countries, it is the leading
cause of blindness.
Etiopathogenesis
Risk factors associated with occurence of DR are:
1. Duration of diabetes is the most important
determining factor. Roughly 50 percent of patients
develop DR after 10 years, 70 percent after 20
years and 90 percent after 30 years of onset of
the disease.
2. Sex. Incidence is more in females than males (4:3).
3. Poor metabolic control is less important than
duration, but is nevertheless relevant to the
development and progression of DR.
4. Heredity. It is transmitted as a recessive trait
without sex linkage. The effect of heredity is
more on the proliferative retinopathy.
5. Pregnancy may accelerate the changes of diabetic
retinopathy.
6. Hypertension, when associated, may also
accentuate the changes of diabetic retinopathy.
7. Other risk factors include smoking, obesity and
hyperlipidemia.
Classification
Diabetic retinopathy has been variously classified.
Presently followed classification is as follows:
I. Non-proliferative diabetic retinopathy (NPDR)
Mild NPDR
Moderate NPDR
Severe NPDR
Very severe NPDR
II. Proliferative diabetic retinopathy (PDR)
III. Diabetic maculopathy
IV. Advanced diabetic eye disease (ADED)
I. Non-proliferative diabetic retinopathy (NPDR)
Ophthalmoscopic features of NPDR include:
Microaneurysms in the macular area (the earliest
detectable lesion).
Retinal haemorrhages both deep (dot and blot
haemorrhages) and superficial haemorrhages
(flame-shaped). Hard exudates-yellowish-white waxy-looking
patches are arranged in clumps or in circinate
pattern. These are commonly seen in the macular
area.
Retinal oedema characterized by retinal
thickening.
Cotton-wool spots (if > 8, there is high risk of
developing PDR).
Venous abnormalities, beading, looping and
dilatation.
Intraretinal microvascular abnormalities
(IRMA).
Dark-blot haemorrhages representing haemorrhagic
retinal infarcts.
On the basis of severity of the above findings the
NPDR has been further classified as under:
1. Mild NPDR (Fig. 11.14A).
At least one microaneurysm or intraretinal
hemorrhage.
Hard/soft exudates may or may not be present.
2. Moderate NPDR (Fig. 11.14B)
Moderate microaneurysms/intraretinal hemorrhage.
Early mild IRMA.
Hard/soft exudates may or may not present.
3. Severe NPDR. Any one of the following (4-2-1
Rule) (Fig. 11.14C):
Four quadrants of severe microaneurysms/
intraretinal hemorrhages.
Two quadrants of venous beading.
One quadrant of IRMA changes.
4. Very severe NPDR. Any two of the following
(4-2-1 Rule) (Fig. 11.14D):
Four quadrants of severe microaneurysms/
intraretinal hemorrhages.
Two quadrants of venous beading.
One quadrant of IRMA changes.
II. Proliferative diabetic retinopathy (PDR)
Proliferative diabetic retinopathy (Figs. 11.14 E&F)
develops in more than 50 percent of cases after about
25 years of the onset of disease. Therefore, it is more
common in patients with juvenile onset diabetes. The
hallmark of PDR is the occurrence of
neovascularisation over the changes of very severe
non-proliferative diabetic retinopathy. It is
characterised by proliferation of new vessels from
the capillaries, in the form of neovascularisation at
the optic disc (NVD) and/or elsewhere (NVE) in the
fundus, usually along the course of the major temporal
retinal vessels. These new vessels may proliferate in
the plane of retina or spread into the vitreous as
vascular fronds. Later on condensation of connective
tissue around the new vessels results in formation of
fibrovascular epiretinal membrane. Vitreous
detachment and vitreous haemorrhage may occur in
this stage.
Types. On the basis of high risk characteristics
(HRCs) described by diabetic retinopathy study
(DRS) group, the PDR can be further classified as
below:
1. PDR without HRCs (Early PDR) (Fig. 11.14E), and
2. PDR with HRCs (Advanced PDR). High risk
characteristics (HRC) of PDR are as follows
(Fig. 11.14F):
NVD 1/4 to 1/3 of disc area with or without
vitreous haemorrhage (VH) or pre-retinal
haemorrhage (PRH)
NVD < 1/4 disc area with VH or PRH
NVE > 1/2 disc area with VH or PRH
III. Diabetic maculopathy
Changes in macular region need special mention, due
to their effect on vision. These changes may be associated with non-proliferative diabetic
retinopathy (NPDR) or proliferative diabetic
retinopathy (PDR). The diabetic macular edema occurs
due to increased permeability of the retinal capillaries.
It is termed as clinically significant macular edema
(CSME) if one of the following three criteria are
present on slit-lamp examination with 90D lens:
Thickening of the retina at or within 500 micron
of the centre of the fovea.
Hard exudate at or within 500 micron of the centre
of fovea associated with adjacent retinal
thickening.
Development of a zone of retinal thickening one
disc diameter or larger in size, at least a part of
which is within one disc diameter of the foveal
centre.
Clinico-angiographically diabetic maculopathy can be
classified into four types:
1. Focal exudative maculopathy (Fig. 11.14G). It is
characterised by microaneurysms, haemorrhages,
macular oedema and hard exudates which are usually
arranged in a circinate pattern. Fluorescein
angiography reveals focal leakage with adequate
macular perfusion.
2. Diffuse exudative maculopathy. It is characterised
by diffuse retinal oedema and thickening throughout
the posterior pole, with relatively few hard exudates.
Fluorescein angiography reveals diffuse leakage at
the posterior pole.
3. Ischaemic maculopathy. It occurs due to
microvascular blockage. Clinically it is characterised
by marked visual loss with microaneurysms,
haemorrhages, mild or no macular oedema and a few
hard exudates. Fluorescein angiography shows areas
of non-perfusion which in early cases are in the form
of enlargement of foveal avascular zone (FAZ), later
on areas of capillary dropouts are seen and in
advanced cases precapillary arterioles are blocked.
4. Mixed maculopathy. In it combined features of
ischaemic and exudative maculopathy are present.
IV. Advanced diabetic eye disease
It is the end result of uncontrolled proliferative
diabetic retinopathy. It is marked by complications
such as:
Persistent vitreous haemorrhage,
Tractional retinal detachment and
Neovascular glaucoma.
Investigations
Urine examination,
Blood sugar estimation.
Fundus fluorescein angiography should be carried
out to elucidate areas of neovascularisation,
leakage and capillary nonperfusion.
Management
I. Screening for diabetic retinopathy. To prevent
visual loss occurring from diabetic retinopathy a
periodic follow-up is very important for a timely
intervention. The recommendations for periodic
fundus examination are as follows:
Every year, till there is no diabetic retinopathy or
there is mild NPDR.
Every 6 months, in moderate NPDR.
Every 3 months, in severe NPDR.
Every 2 months, in PDR with no high risk
characteristic.
II. Medical treatment. Besides laser and surgery to
the eyes (as indicated and described below), the
medical treatment also plays an essential role. Medical
treatment for diabetic retinopathy can be discussed
as:
1. Control of systemic risk factors is known to
influence the occurrence, progression and effect
of laser treatment on DR. The systemic risk factors
which need attention are.
Strict metabolic control of blood sugar,
Lipid reduction,
Control of associated anaemia, and
Control of associated hypoproteinemia
2. Role of pharmacological modulation. Pharmacological
inhibition of certain biochemical
pathways involved in the pathogenesis of retinal
changes in diabetes is being evaluated These
include:
Protein kinase C (PKC) inhbitors,
Vascular endothelial growth factors (VEGF)
inhibitors,
Aldose reductase and ACE inhibitors, and
Antioxidants such as vitamin E
3. Role of intravitreal steroids in reducing diabetic
macular oedema is also being stressed recently
by following modes of administration:
Flucinolone acetonide intravitreal implant and
Intravitreal injection of triamcinolone
(2 to 4 mg)
III. Photocoagulation. It remains the mainstay in the
treatment of diabetic retinopathy and maculopathy.
Either argon or diode laser can be used. The protocol
of laser application is different for macula and rest of
the retina as follows (Fig. 11.15):
i. Macular photocoagulation. Macula is treated
by laser only if there is clinically significant
macular oedema (CSME). Laser treatment is
contraindicated in ischaemic diabetic maculopathy.
In patients with PDR associated with CSME,
macular photo-coagulation should be considered
first i.e., before PRP since the latter may worsen
macular oedema. Macular photocoagulation
includes two techniques:
Focal treatment (Fig. 11.15A) with argon laser
is carried out for all lesions (microaneurysms,
IRMA or short capillary segments) 500-3000
microns from the centre of the macula, believed
to be leaking and causing CSME. Spot size of
100-200 μm of 0.1 second duration is used.
Grid treatment. Grid pattern laser burns are
applied in the macular area for diffuse diabetic
macular oedema (Fig. 11.15B).
ii. Panretinal photocoagulation (PRP) or scatter
laser consists of 1200-1600 spots, each 500 μm in
size and 0.1 sec. duration. Laser burns are applied
2-3 disc areas from the centre of the macula
extending peripherally to the equator (Fig. 11.15C).
In PRP temporal quadrant of retina is first
coagulated. PRP produces destruction of
ischaemic retina which is responsible for the
production of vasoformative factors.
Indications for PRP are:
PDR with HRCs,
Neovascularization of iris (NVI),
Severe NPDR associated with:
– Poor compliance for follow up,
– Before cataract surgery/YAG capsulotomy,
– Renal failure,
– One-eyed patient, and
– Pregnancy
IV. Surgical treatment. It is required in advanced
cases of PDR. Pars plana vitrectomy is indicated for
dense persistent vitreous haemorrhage, tractional
retinal detachment, and epiretinal membranes.
Associated retinal detachment also needs surgical
repair.
RETINAL VEIN OCCLUSION
It is more common than the artery occlusion. It
typically affects elderly patients in sixth or seventh
decade of life.
Etiology
1. Pressure on the vein by a sclerotic retinal artery
where the two share a common adventitia (e.g.,
just behind the lamina cribrosa and at
arteriovenous crossings).
2. Hyperviscosity of blood as in polycythemia,
hyperlipidemia and macroglobulinemia.
3. Periphlebitis retinae which can be central or
peripheral.
4. Raised introcular pressure. Central retinal vein
occlusion is more common in patients with primary
open-angle glaucoma.
5. Local causes are orbital cellulitis, facial erysipelas
and cavernous sinus thrombosis.
Classification
1. Central retinal vein occlusion (CRVO) It may be
non-ischaemic CRVO (venous stasis retinopathy)
or ischaemic CRVO (haemorrhagic retinopathy).
2. Branch retinal vein occlusion (BRVO)
Non-ischaemic CRVO
Non-ischaemic CRVO (venous stasis retinopathy)
is the most common clinical variety (75%). It is
characterised by mild to moderate visual loss. Fundus
examination in early cases (Fig. 11.9) reveals mild
venous congestion and tortuosity, a few superficial
flame-shaped haemorrhages more in the peripheral
than the posterior retina, mild papilloedema and mild
or no macular oedema. In late stages (after 6-9
months), there appears sheathing around the main
veins, and a few cilioretinal collaterals around the
disc. Retinal haemorrhages are partly absorbed.
Macula may show chronic cystoid oedema in
moderate cases or may be normal in mild cases.
Treatment is usually not required. The condition
resolves with almost normal vision in about 50 percent
cases. Visual loss in rest of the cases is due to chronic
cystoid macular oedema, for which no treatment is
effective. However, a course of oral steroids for 8-12
weeks may be effective.Ischaemic CRVO
Ischaemic CRVO (Haemorrhagic retinopathy) refers
to acute (sudden) complete occlusion of central retinal
vein. It is characterised by marked sudden visual loss.
Fundus examination in early cases (Fig. 11.10) reveals
massive engorgement, congestion and tortuousity
of retinal veins, massive retinal haemorrhages (almost whole fundus is full of haemorrhages giving a
‘splashed-tomato’ appearance), numerous soft
exudates, and papilloedema. Macular area is full of
haemorrhages and is severely oedematous. In late
stages, marked sheathing around veins and
collaterals is seen around the disc.
Neovascularisation may be seen at the disc (NVD) or
in the periphery (NVE). Macula shows marked
pigmentary changes and chronic cystoid oedema.
The pathognomic features for differentiating
ischaemic CRVO from non-ischaemic CRVO are
presence of relative afferent pupillary defect (RAPD),
visual field defects and reduced amplitude of b-wave
of electroretinogram (ERG).
Complications. Rubeosis iridis and neovascular
glaucoma (NVG) occur in more than 50 percent cases
within 3 months (so also called as 90 days glaucoma),
A few cases develop vitreous haemorrhage and
proliferative retinopathy.
Treatment. Panretinal photocoagulation (PRP) or
cryo-application, if the media is hazy, may be required
to prevent neovascular glaucoma in patients with
widespread capillary occlusion. Photocoagulation
should be carried out when most of the intraretinal
blood is absorbed, which usually takes about 3-4
months.
Branch retinal vein occlusion (BRVO)
It is more common than the central retinal vein
occlusion. It may occur at the following sites: main
branch at the disc margin causing hemispheric
occlusion, major branch vein away from the disc, at
A-V crossing causing quadrantic occlusion and
small macular or peripheral branch occlusion. In
branch vein occlusion oedema and haemorrhages are
limited to the area drained by the affected vein (Fig.
11.11). Vision is affected only when the macular area
is involved. Secondary glaucoma occurs rarely in
these cases. Chronic macular oedema and
neovasculari-sation may occur as complications of
BRVO in about one third cases.
Treatment. Grid photocoagulation may be required
in patients with chronic macular oedema. In patients
with neovascularisation, scatter photocoagulation
should be carried out.
typically affects elderly patients in sixth or seventh
decade of life.
Etiology
1. Pressure on the vein by a sclerotic retinal artery
where the two share a common adventitia (e.g.,
just behind the lamina cribrosa and at
arteriovenous crossings).
2. Hyperviscosity of blood as in polycythemia,
hyperlipidemia and macroglobulinemia.
3. Periphlebitis retinae which can be central or
peripheral.
4. Raised introcular pressure. Central retinal vein
occlusion is more common in patients with primary
open-angle glaucoma.
5. Local causes are orbital cellulitis, facial erysipelas
and cavernous sinus thrombosis.
Classification
1. Central retinal vein occlusion (CRVO) It may be
non-ischaemic CRVO (venous stasis retinopathy)
or ischaemic CRVO (haemorrhagic retinopathy).
2. Branch retinal vein occlusion (BRVO)
Non-ischaemic CRVO
Non-ischaemic CRVO (venous stasis retinopathy)
is the most common clinical variety (75%). It is
characterised by mild to moderate visual loss. Fundus
examination in early cases (Fig. 11.9) reveals mild
venous congestion and tortuosity, a few superficial
flame-shaped haemorrhages more in the peripheral
than the posterior retina, mild papilloedema and mild
or no macular oedema. In late stages (after 6-9
months), there appears sheathing around the main
veins, and a few cilioretinal collaterals around the
disc. Retinal haemorrhages are partly absorbed.
Macula may show chronic cystoid oedema in
moderate cases or may be normal in mild cases.
Treatment is usually not required. The condition
resolves with almost normal vision in about 50 percent
cases. Visual loss in rest of the cases is due to chronic
cystoid macular oedema, for which no treatment is
effective. However, a course of oral steroids for 8-12
weeks may be effective.Ischaemic CRVO
Ischaemic CRVO (Haemorrhagic retinopathy) refers
to acute (sudden) complete occlusion of central retinal
vein. It is characterised by marked sudden visual loss.
Fundus examination in early cases (Fig. 11.10) reveals
massive engorgement, congestion and tortuousity
of retinal veins, massive retinal haemorrhages (almost whole fundus is full of haemorrhages giving a
‘splashed-tomato’ appearance), numerous soft
exudates, and papilloedema. Macular area is full of
haemorrhages and is severely oedematous. In late
stages, marked sheathing around veins and
collaterals is seen around the disc.
Neovascularisation may be seen at the disc (NVD) or
in the periphery (NVE). Macula shows marked
pigmentary changes and chronic cystoid oedema.
The pathognomic features for differentiating
ischaemic CRVO from non-ischaemic CRVO are
presence of relative afferent pupillary defect (RAPD),
visual field defects and reduced amplitude of b-wave
of electroretinogram (ERG).
Complications. Rubeosis iridis and neovascular
glaucoma (NVG) occur in more than 50 percent cases
within 3 months (so also called as 90 days glaucoma),
A few cases develop vitreous haemorrhage and
proliferative retinopathy.
Treatment. Panretinal photocoagulation (PRP) or
cryo-application, if the media is hazy, may be required
to prevent neovascular glaucoma in patients with
widespread capillary occlusion. Photocoagulation
should be carried out when most of the intraretinal
blood is absorbed, which usually takes about 3-4
months.
Branch retinal vein occlusion (BRVO)
It is more common than the central retinal vein
occlusion. It may occur at the following sites: main
branch at the disc margin causing hemispheric
occlusion, major branch vein away from the disc, at
A-V crossing causing quadrantic occlusion and
small macular or peripheral branch occlusion. In
branch vein occlusion oedema and haemorrhages are
limited to the area drained by the affected vein (Fig.
11.11). Vision is affected only when the macular area
is involved. Secondary glaucoma occurs rarely in
these cases. Chronic macular oedema and
neovasculari-sation may occur as complications of
BRVO in about one third cases.
Treatment. Grid photocoagulation may be required
in patients with chronic macular oedema. In patients
with neovascularisation, scatter photocoagulation
should be carried out.
HYPERTENSIVE RETINOPATHY
It refers to fundus changes occurring in patients
suffering from systemic hypertension.
Pathogenesis
Three factors which play role in the pathogenesis of
hypertensive retinopathy are vasoconstriction,
arteriosclerosis and increased vascular permeability.
1. Vasoconstriction. Primary response of the retinal
arterioles to raised blood pressure is narrowing
(vasoconstriction) and is related to the severity of
hypertension. It occurs in pure form in young
individuals, but is affected by the pre-existing
involutional sclerosis in older patients.2. Arteriosclerotic changes which manifest as
changes in arteriolar reflex and A-V nipping result
from thickening of the vessel wall and are a reflection
of the duration of hypertension. In older patients
arteriosclerotic changes may preexist due to
involutional sclerosis.
3. Increased vascular permeability results from
hypoxia and is responsible for haemorrhages, exudates
and focal retinal oedema.
Grading of hypertensive retinopathy
Keith and Wegner (1939) have classified
hypertensive retinopathy changes into following four
grades:
Grade I (Fig. 11.12A). It consists of mild
generalized arteriolar attenuation, particularly of
small branches, with broadening of the arteriolar
light reflex and vein concealment.
Grade II (Fig. 11.12B). It comprises marked
generalized narrowing and focal attenuation of
arterioles associated with deflection of veins at
arteriovenous crossings (Salus’ sign).
Grade III (Fig. 11.12C). This consists of Grade II
changes plus copper-wiring of arterioles, banking
of veins distal to arteriovenous crossings (Bonnet
sign), tapering of veins on either side of the
crossings (Gunn sign) and right-angle deflection
of veins (Salu’s sign). Flame-shaped
haemorrhages, cotton-wool spots and hard
exudates are also present.
Grade IV (Fig. 11.12D). This consists of all
changes of Grade III plus silver-wiring of arterioles
and papilloedema.Clinical types
Clinically, hypertensive retinopathy may occur in four
circumstances:
1. Hypertension with involutionary (senile) sclerosis.
When hypertension occurs in elderly patients (after
the age of 50 years) in the presence of involutionary
sclerosis the fundus changes comprise augmented
arteriosclerotic retinopathy.
2. Hypertension without sclerosis. It occurs in young
people, where elastic retinal arterioles are exposed to
raised blood pressure for a short duration. There are
few retinal signs. The arterioles are constricted, pale
and straight with acute-angled branching. There are
minimal signs of arteriovenous crossing. Occasionally
small haemorrhages may be found. Exudates and
papilloedema are never seen.
3. Hypertension with compensatory arteriolar
sclerosis. This condition is seen in young patients
with prolonged benign hypertension usually
associated with benign nephrosclerosis. The young
arterioles respond by proliferative and fibrous
changes in the media (compensatory arteriolar
sclerosis). Advanced fundus changes in these
patients have been described as ‘albuminuric or renal
retinopathy’.
4. Malignant hypertension. It is not a separate
variety of hypertension, but is an expression of its
rapid progression to a serious degree in a patient
with relatively young arterioles undefended by
fibrosis. The fundus picture is characterised by
marked arteriolar narrowing, papilloedema (an
essential feature of malignant hypertension), retinal
oedema over the posterior pole, clusters of superficial
flame-shaped haemorrhages and an abundance of
cotton wool patches.
RETINOPATHY IN PREGNANCY-INDUCED
HYPERTENSION
Pregnancy-induced hypertension (PIH), previously
known as ‘toxaemia of pregnancy’, is a disease of
unknown etiology characterised by raised blood
pressure, proteinuria and generalised oedema. Retinal
changes are liable to occur in this condition when
blood pressure rises above 160/100 mm of Hg and are
marked when blood pressure rises above 200/130 mm
of Hg. Earliest changes consist of narrowing of nasal
arterioles, followed by generalised narrowing. Severe
persistent spasm of vessels causes retinal hypoxia
characterised by appearance of ‘cotton wool spots’
and superficial haemorrhages. If pregnancy is allowed
to continue, further progression of retinopathy occurs
rapidly. Retinal oedema and exudation is usually
marked and may be associated with ‘macular star’ or
‘flat macular detachment’. Rarely it may be
complicated by bilateral exudative retinal detachment.
Prognosis for retinal reattachment is good, as it
occurs spontaneously within a few days of
termination of pregnancy.
Management. Changes of retinopathy are reversible
and disappear after the delivery, unless organic
vascular disease is established. Therefore, in preorganic
stage when patient responds well to
conservative treatment, the pregnancy may justifiably
be continued under close observation. However, the
advent of hypoxic retinopathy (soft exudates, retinal
oedema and haemorrhages) should be considered an
indication for termination of pregnancy; otherwise,
permanent visual loss or even loss of life (of both
mother and foetus) may occur.
suffering from systemic hypertension.
Pathogenesis
Three factors which play role in the pathogenesis of
hypertensive retinopathy are vasoconstriction,
arteriosclerosis and increased vascular permeability.
1. Vasoconstriction. Primary response of the retinal
arterioles to raised blood pressure is narrowing
(vasoconstriction) and is related to the severity of
hypertension. It occurs in pure form in young
individuals, but is affected by the pre-existing
involutional sclerosis in older patients.2. Arteriosclerotic changes which manifest as
changes in arteriolar reflex and A-V nipping result
from thickening of the vessel wall and are a reflection
of the duration of hypertension. In older patients
arteriosclerotic changes may preexist due to
involutional sclerosis.
3. Increased vascular permeability results from
hypoxia and is responsible for haemorrhages, exudates
and focal retinal oedema.
Grading of hypertensive retinopathy
Keith and Wegner (1939) have classified
hypertensive retinopathy changes into following four
grades:
Grade I (Fig. 11.12A). It consists of mild
generalized arteriolar attenuation, particularly of
small branches, with broadening of the arteriolar
light reflex and vein concealment.
Grade II (Fig. 11.12B). It comprises marked
generalized narrowing and focal attenuation of
arterioles associated with deflection of veins at
arteriovenous crossings (Salus’ sign).
Grade III (Fig. 11.12C). This consists of Grade II
changes plus copper-wiring of arterioles, banking
of veins distal to arteriovenous crossings (Bonnet
sign), tapering of veins on either side of the
crossings (Gunn sign) and right-angle deflection
of veins (Salu’s sign). Flame-shaped
haemorrhages, cotton-wool spots and hard
exudates are also present.
Grade IV (Fig. 11.12D). This consists of all
changes of Grade III plus silver-wiring of arterioles
and papilloedema.Clinical types
Clinically, hypertensive retinopathy may occur in four
circumstances:
1. Hypertension with involutionary (senile) sclerosis.
When hypertension occurs in elderly patients (after
the age of 50 years) in the presence of involutionary
sclerosis the fundus changes comprise augmented
arteriosclerotic retinopathy.
2. Hypertension without sclerosis. It occurs in young
people, where elastic retinal arterioles are exposed to
raised blood pressure for a short duration. There are
few retinal signs. The arterioles are constricted, pale
and straight with acute-angled branching. There are
minimal signs of arteriovenous crossing. Occasionally
small haemorrhages may be found. Exudates and
papilloedema are never seen.
3. Hypertension with compensatory arteriolar
sclerosis. This condition is seen in young patients
with prolonged benign hypertension usually
associated with benign nephrosclerosis. The young
arterioles respond by proliferative and fibrous
changes in the media (compensatory arteriolar
sclerosis). Advanced fundus changes in these
patients have been described as ‘albuminuric or renal
retinopathy’.
4. Malignant hypertension. It is not a separate
variety of hypertension, but is an expression of its
rapid progression to a serious degree in a patient
with relatively young arterioles undefended by
fibrosis. The fundus picture is characterised by
marked arteriolar narrowing, papilloedema (an
essential feature of malignant hypertension), retinal
oedema over the posterior pole, clusters of superficial
flame-shaped haemorrhages and an abundance of
cotton wool patches.
RETINOPATHY IN PREGNANCY-INDUCED
HYPERTENSION
Pregnancy-induced hypertension (PIH), previously
known as ‘toxaemia of pregnancy’, is a disease of
unknown etiology characterised by raised blood
pressure, proteinuria and generalised oedema. Retinal
changes are liable to occur in this condition when
blood pressure rises above 160/100 mm of Hg and are
marked when blood pressure rises above 200/130 mm
of Hg. Earliest changes consist of narrowing of nasal
arterioles, followed by generalised narrowing. Severe
persistent spasm of vessels causes retinal hypoxia
characterised by appearance of ‘cotton wool spots’
and superficial haemorrhages. If pregnancy is allowed
to continue, further progression of retinopathy occurs
rapidly. Retinal oedema and exudation is usually
marked and may be associated with ‘macular star’ or
‘flat macular detachment’. Rarely it may be
complicated by bilateral exudative retinal detachment.
Prognosis for retinal reattachment is good, as it
occurs spontaneously within a few days of
termination of pregnancy.
Management. Changes of retinopathy are reversible
and disappear after the delivery, unless organic
vascular disease is established. Therefore, in preorganic
stage when patient responds well to
conservative treatment, the pregnancy may justifiably
be continued under close observation. However, the
advent of hypoxic retinopathy (soft exudates, retinal
oedema and haemorrhages) should be considered an
indication for termination of pregnancy; otherwise,
permanent visual loss or even loss of life (of both
mother and foetus) may occur.
Retina Layers And Blood Supply
Microscopic structure
Retina consists of 3 types of cells and their synapses
arranged (from without inward) in the following ten
layers (Fig. 11.2):
1. Pigment epithelium. It is the outermost layer of
retina. It consists of a single layer of cells
containing pigment. It is firmly adherent to the
underlying basal lamina (Bruch’s membrane) of
the choroid.
2. Layer of rods and cones. Rods and cones are the
end organs of vision and are also known as
photoreceptors. Layer of rods and cones contains
only the outer segments of photoreceptor cells
arranged in a palisade manner. There are about
120 millions rods and 6.5 millions cones. Rods
contain a photosensitive substance visual purple
(rhodopsin) and subserve the peripheral vision
and vision of low illumination (scotopic vision).
Cones also contain a photosensitive substance
and are primarily responsible for highly
discriminatory central vision (photopic vision)
and colour vision.
3. External limiting membrane. It is a fenesterated
membrane, through which pass processes of
the rods and cones.
4. Outer nuclear layer. It consists of nuclei of the
rods and cones.
5. Outer plexiform layer. It consists of connections
of rod spherules and cone pedicles with the
dendrites of bipolar cells and horizontal cells.
6. Inner nuclear layer. It mainly consists of cell
bodies of bipolar cells. It also contains cell
bodies of horizontal amacrine and Muller’s cells
and capillaries of central artery of retina. The
bipolar cells constitute the first order neurons.
7. Inner plexiform layer. It essentially consists of
connections between the axons of bipolar cells
dendrites of the ganglion cells, and processes
of amacrine cells.
8. Ganglion cell layer. It mainly contains the cell
bodies of ganglion cells (the second order
neurons of visual 7pathway). There are two
types of ganglion cells. The midget ganglioncells are present in the macular region and the
dendrite of each such cell synapses with the
axon of single bipolar cell. Polysynaptic
ganglion cells lie predominantly in peripheral
retina and each such cell may synapse with
upto a hundred bipolar cells.
9. Nerve fibre layer (stratum opticum) consists of
axons of the ganglion cells, which pass through
the lamina cribrosa to form the optic nerve. For
distribution and arrangement of retinal nerve
fibres see Figs. 9.11 and 9.12, respectively and
page 216.
10. Internal limiting membrane. It is the innermost
layer and separates the retina from vitreous. It
is formed by the union of terminal expansions
of the Muller’s fibres, and is essentially a basement membrane.
Blood supply
Outer four layers of the retina, viz, pigment
epithelium, layer of rods and cones, external limiting membrane and outer nuclear layer get
their nutrition from the choroidal vessels.
Inner six layers get their supply from the central
retinal artery, which is a branch of the ophthalmic
artery.
Central retinal artery emerges from centre of the
physiological cup of the optic disc and divides
into four branches, namely the superior-nasal,
superior-temporal, inferior-nasal and inferiortemporal.
These are end arteries i.e., they do not
anastomose with each other.
The retinal veins. These follow the pattern of the
retinal arteries. The central retinal vein drains into
the cavernous sinus directly or through the
superior ophthalmic vein. The only place where
the retinal system anastomosis with ciliary system
is in the region of lamina cribrosa.
Retina consists of 3 types of cells and their synapses
arranged (from without inward) in the following ten
layers (Fig. 11.2):
1. Pigment epithelium. It is the outermost layer of
retina. It consists of a single layer of cells
containing pigment. It is firmly adherent to the
underlying basal lamina (Bruch’s membrane) of
the choroid.
2. Layer of rods and cones. Rods and cones are the
end organs of vision and are also known as
photoreceptors. Layer of rods and cones contains
only the outer segments of photoreceptor cells
arranged in a palisade manner. There are about
120 millions rods and 6.5 millions cones. Rods
contain a photosensitive substance visual purple
(rhodopsin) and subserve the peripheral vision
and vision of low illumination (scotopic vision).
Cones also contain a photosensitive substance
and are primarily responsible for highly
discriminatory central vision (photopic vision)
and colour vision.
3. External limiting membrane. It is a fenesterated
membrane, through which pass processes of
the rods and cones.
4. Outer nuclear layer. It consists of nuclei of the
rods and cones.
5. Outer plexiform layer. It consists of connections
of rod spherules and cone pedicles with the
dendrites of bipolar cells and horizontal cells.
6. Inner nuclear layer. It mainly consists of cell
bodies of bipolar cells. It also contains cell
bodies of horizontal amacrine and Muller’s cells
and capillaries of central artery of retina. The
bipolar cells constitute the first order neurons.
7. Inner plexiform layer. It essentially consists of
connections between the axons of bipolar cells
dendrites of the ganglion cells, and processes
of amacrine cells.
8. Ganglion cell layer. It mainly contains the cell
bodies of ganglion cells (the second order
neurons of visual 7pathway). There are two
types of ganglion cells. The midget ganglioncells are present in the macular region and the
dendrite of each such cell synapses with the
axon of single bipolar cell. Polysynaptic
ganglion cells lie predominantly in peripheral
retina and each such cell may synapse with
upto a hundred bipolar cells.
9. Nerve fibre layer (stratum opticum) consists of
axons of the ganglion cells, which pass through
the lamina cribrosa to form the optic nerve. For
distribution and arrangement of retinal nerve
fibres see Figs. 9.11 and 9.12, respectively and
page 216.
10. Internal limiting membrane. It is the innermost
layer and separates the retina from vitreous. It
is formed by the union of terminal expansions
of the Muller’s fibres, and is essentially a basement membrane.
Blood supply
Outer four layers of the retina, viz, pigment
epithelium, layer of rods and cones, external limiting membrane and outer nuclear layer get
their nutrition from the choroidal vessels.
Inner six layers get their supply from the central
retinal artery, which is a branch of the ophthalmic
artery.
Central retinal artery emerges from centre of the
physiological cup of the optic disc and divides
into four branches, namely the superior-nasal,
superior-temporal, inferior-nasal and inferiortemporal.
These are end arteries i.e., they do not
anastomose with each other.
The retinal veins. These follow the pattern of the
retinal arteries. The central retinal vein drains into
the cavernous sinus directly or through the
superior ophthalmic vein. The only place where
the retinal system anastomosis with ciliary system
is in the region of lamina cribrosa.
RETINAL ARTERY OCCLUSION
Etiology
Occlusive disorders of retinal vessels are more
common in patients suffering from hypertension and
other cardiovascular diseases. Common causes of
retinal artery occlusion are:
Atherosclerosis-related thrombosis at the level
of lamina cribrosa is the most common cause
(75%) of CRAO.
Emboli from the carotid artery and those of
cardiac origin account for about 20% cases of
CRAO.
Retinal arteritis with obliteration (associated
with giant cell arteritis) and periarteritis (associated
with polyarteritis nodosa, systemic lupus erythematosus,
Wegner’s granulomatosis and scleroderma)
are other causes of CRAO.
Angiospasm is a rare cause of retinal artery
occlusion. It is commonly associated with
amaurosis.
Raised intraocular pressure may occasionally be
associated with obstruction of retinal arteries for
example due to tight encirclage in retinal
detachment surgery.
Thrombophilic disorders such as inherited
defects of anticoagulants may occasionally be
associated with CRAO in young individuals.
Clinical features
Clinically retinal artery occlusion may present as
central retinal artery occlusion or branch artery
occlusion. It is more common in males than females.
It is usually unilateral but rarely may be bilateral (1 to
2% cases).
1. Central retinal artery occlusion (CRAO). It occurs
due to obstruction at the level of lamina cribrosa.
Symptoms. Patient complains of sudden painless loss
of vision.
Signs. Direct pupillary light reflex is absent. On
ophthalmoscopic examination retinal arteries are
markedly narrowed but retinal veins look almost
normal. Retina becomes milky white due to oedema.
Central part of the macular area shows cherry-red
spot due to vascular choroid shining through the thin
retina of this region. In eyes with a cilioretinal artery,
part of the macular will remain normal (Fig. 11.7). Blood
column within the retinal veins is segmented (cattletrucking).
After a few weeks the oedema subsides,
and atrophic changes occur which include grossly
attenuated thread-like arteries and consecutive optic
atrophy (see page 302, 303 Fig 12.12B).
2. Branch retinal artery occlusion (BRAO). It usually
occurs following lodgement of embolus at a
bifurcation. Retina distal to occlusion becomes
oedematous with narrowed arterioles (Fig. 11.8). Later
on the involved area is atrophied leading to permanent
sectoral visual field defect.Management
Treatment of central retinal artery occlusion is
unsatisfactory, as retinal tissue cannot survive
ischaemia for more than a few hours. The emergency
treatment should include:
1. Immediate lowering of intraocular pressure by
intravenous mannitol and intermittent ocular
massage. It may aid the arterial perfusion and
also help in dislodging the embolus. Even
paracentesis of anterior chamber has been
recommended for this purpose.
2. Vasodilators and inhalation of a mixture of 5
percent carbon dioxide and 95 percent oxygen
(practically patient should be asked to breathe in
a polythene bag) may help by relieving element
of angiospasm.
3. Anticoagulants may be helpful in some cases.
4. Intravenous steroids are indicated in patients
with giant cell arteritis.
Complications
In some cases ‘neovascular glaucoma’ with incidence
varying from 1% to 5%, may occur as a delayed
complication of central retinal artery occlusion.
Occlusive disorders of retinal vessels are more
common in patients suffering from hypertension and
other cardiovascular diseases. Common causes of
retinal artery occlusion are:
Atherosclerosis-related thrombosis at the level
of lamina cribrosa is the most common cause
(75%) of CRAO.
Emboli from the carotid artery and those of
cardiac origin account for about 20% cases of
CRAO.
Retinal arteritis with obliteration (associated
with giant cell arteritis) and periarteritis (associated
with polyarteritis nodosa, systemic lupus erythematosus,
Wegner’s granulomatosis and scleroderma)
are other causes of CRAO.
Angiospasm is a rare cause of retinal artery
occlusion. It is commonly associated with
amaurosis.
Raised intraocular pressure may occasionally be
associated with obstruction of retinal arteries for
example due to tight encirclage in retinal
detachment surgery.
Thrombophilic disorders such as inherited
defects of anticoagulants may occasionally be
associated with CRAO in young individuals.
Clinical features
Clinically retinal artery occlusion may present as
central retinal artery occlusion or branch artery
occlusion. It is more common in males than females.
It is usually unilateral but rarely may be bilateral (1 to
2% cases).
1. Central retinal artery occlusion (CRAO). It occurs
due to obstruction at the level of lamina cribrosa.
Symptoms. Patient complains of sudden painless loss
of vision.
Signs. Direct pupillary light reflex is absent. On
ophthalmoscopic examination retinal arteries are
markedly narrowed but retinal veins look almost
normal. Retina becomes milky white due to oedema.
Central part of the macular area shows cherry-red
spot due to vascular choroid shining through the thin
retina of this region. In eyes with a cilioretinal artery,
part of the macular will remain normal (Fig. 11.7). Blood
column within the retinal veins is segmented (cattletrucking).
After a few weeks the oedema subsides,
and atrophic changes occur which include grossly
attenuated thread-like arteries and consecutive optic
atrophy (see page 302, 303 Fig 12.12B).
2. Branch retinal artery occlusion (BRAO). It usually
occurs following lodgement of embolus at a
bifurcation. Retina distal to occlusion becomes
oedematous with narrowed arterioles (Fig. 11.8). Later
on the involved area is atrophied leading to permanent
sectoral visual field defect.Management
Treatment of central retinal artery occlusion is
unsatisfactory, as retinal tissue cannot survive
ischaemia for more than a few hours. The emergency
treatment should include:
1. Immediate lowering of intraocular pressure by
intravenous mannitol and intermittent ocular
massage. It may aid the arterial perfusion and
also help in dislodging the embolus. Even
paracentesis of anterior chamber has been
recommended for this purpose.
2. Vasodilators and inhalation of a mixture of 5
percent carbon dioxide and 95 percent oxygen
(practically patient should be asked to breathe in
a polythene bag) may help by relieving element
of angiospasm.
3. Anticoagulants may be helpful in some cases.
4. Intravenous steroids are indicated in patients
with giant cell arteritis.
Complications
In some cases ‘neovascular glaucoma’ with incidence
varying from 1% to 5%, may occur as a delayed
complication of central retinal artery occlusion.
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