Hypermetropia

Hypermetropia (hyperopia) or long-sightedness is the
refractive state of the eye wherein parallel rays of
light coming from infinity are focused behind the
retina with accommodation being at rest (Fig. 3.22).
Thus, the posterior focal point is behind the retina,
which therefore receives a blurred image.

Etiology
Hypermetropia may be axial, curvatural, index,
positional and due to absence of lens.
1. Axial hypermetropia is by far the commonest
form. In this condition the total refractive power
of eye is normal but there is an axial shortening
of eyeball. About 1–mm shortening of the anteroposterior
diameter of the eye results in 3 dioptres
of hypermetropia.
2. Curvatural hypermetropia is the condition in
which the curvature of cornea, lens or both is
flatter than the normal resulting in a decrease in
the refractive power of eye. About 1 mm increase
in radius of curvature results in 6 dioptres of
hypermetropia.
3. Index hypermetropia occurs due to decrease in
refractive index of the lens in old age. It may also
occur in diabetics under treatment.
4. Positional hypermetropia results from posteriorly
placed crystalline lens.
5. Absence of crystalline lens either congenitally or
acquired (following surgical removal or posterior
dislocation) leads to aphakia — a condition of
high hypermetropia.
Clinical types
There are three clinical types of hypermetropia:
1. Simple or developmental hypermetropia is the
commonest form. It results from normal biological
variations in the development of eyeball. It includes
axial and curvatural hypermetropia.
2. Pathological hypermetropia results due to either
congenital or acquired conditions of the eyeball which
are outside the normal biological variations of the
development. It includes :
Index hypermetropia (due to acquired cortical
sclerosis),
Positional hypermetropia (due to posterior
subluxation of lens),
Aphakia (congenital or acquired absence of lens)
and
Consecutive hypermetropia (due to surgically
over-corrected myopia).
3. Functional hypermetropia results from paralysis
of accommodation as seen in patients with third nerve
paralysis and internal ophthalmoplegia.
Nomenclature (components of hypermetropia)
Nomenclature for various components of the
hypermetropia is as follows:
Total hypermetropia is the total amount of refractive
error, which is estimated after complete cycloplegia
with atropine. It consists of latent and manifest
hypermetropia.
1. Latent hypermetropia implies the amount of
hypermetropia (about 1D) which is normally
corrected by the inherent tone of ciliary muscle.
The degree of latent hypermetropia is high in
children and gradually decreases with age. The
latent hypermetropia is disclosed when refraction
is carried after abolishing the tone with atropine.
2. Manifest hypermetropia is the remaining portion
of total hypermetropia, which is not corrected by
the ciliary tone. It consists of two components,
the facultative and the absolute hypermetropia.
i. Facultative hypermetropia constitutes that
part which can be corrected by the patient's
accommodative effort.
ii. Absolute hypermetropia is the residual part
of manifest hypermetropia which cannot be
corrected by the patient's accommodative
efforts.
Thus, briefly:
Total hypermetropia = latent + manifest (facultative +
absolute).
Clinical picture
Symptoms
In patients with hypermetropia the symptoms vary
depending upon the age of patient and the degree of
refractive error. These can be grouped as under:
1. Asymptomatic. A small amount of refractive error
in young patients is usually corrected by mild
accommodative effort without producing any
symptom.
2. Asthenopic symptoms. At times the hypermetropia
is fully corrected (thus vision is normal) but due

to sustained accommodative efforts patient
develops asthenopic sysmtoms. These include:
tiredness of eyes, frontal or fronto-temporal
headache, watering and mild photophobia. These
asthenopic symptoms are especially associated
with near work and increase towards evening.
3. Defective vision with asthenopic symptoms.
When the amount of hypermetropia is such that
it is not fully corrected by the voluntary
accommodative efforts, then the patients complain
of defective vision which is more for near than
distance and is associated with asthenopic
symptoms due to sustained accommodative
efforts.
4. Defective vision only. When the amount of
hypermetropia is very high, the patients usually
do not accommodate (especially adults) and there
occurs marked defective vision for near and
distance.
Signs
1. Size of eyeball may appear small as a whole.
2. Cornea may be slightly smaller than the normal.
3. Anterior chamber is comparatively shallow.
4. Fundus examination reveals a small optic disc
which may look more vascular with ill-defined
margins and even may simulate papillitis (though
there is no swelling of the disc, and so it is called
pseudopapillitis). The retina as a whole may shine
due to greater brilliance of light reflections (shot
silk appearance).
5. A-scan ultrasonography (biometry) may reveal a
short antero-posterior length of the eyeball.
Complications
If hypermetropia is not corrected for a long time the
following complications may occur:
1. Recurrent styes, blepharitis or chalazia may
occur, probably due to infection introduced by
repeated rubbing of the eyes, which is often
done to get relief from fatigue and tiredness.
2. Accommodative convergent squint may develop
in children (usually by the age of 2-3 years) due
to excessive use of accommodation.
3. Amblyopia may develop in some cases. It may be
anisometropic (in unilateral hypermetropia),
strabismic (in children developing accommodative
squint) or ametropic (seen in children with
uncorrected bilateral high hypermetropia).
4. Predisposition to develop primary narrow angle
glaucoma. The eye in hypermetropes is small
with a comparatively shallow anterior chamber.
Due to regular increase in the size of the lens
with increasing age, these eyes become prone to
an attack of narrow angle glaucoma. This point
should be kept in mind while instilling mydriatics
in elderly hypermetropes.
Treatment
A. Optical treatment. Basic principle of treatment is
to prescribe convex (plus) lenses, so that the light
rays are brought to focus on the retina (Fig. 3.23).
Fundamental rules for prescribing glasses in
hypermetropia include:

1. Total amount of hypermetropia should always be
discovered by performing refraction under
complete cycloplegia.
2. The spherical correction given should be
comfortably acceptable to the patient. However,
the astigmatism should be fully corrected.
3. Gradually increase the spherical correction at 6
months interval till the patient accepts manifest
hypermetropia.
4. In the presence of accommodative convergent
squint, full correction should be given at the first
sitting.
5. If there is associated amblyopia, full correction
with occlusion therapy should be started.
Modes of prescription of convex lenses
1. Spectacles are most comfortable, safe and
easy method of correcting hypermetropia.
2. Contact lenses are indicated in unilateral
hypermetropia (anisometropia). For cosmetic
reasons, contact lenses should be prescribed
once the prescription has stabilised, otherwise,
they may have to be changed many a times.

Surgical Treatment:

Refractive surgery for hyperopia
In general, refractive surgery for hyperopia is not as
effective or reliable as for myopia. However, following
procedures are used:
1. Holmium laser thermoplasty has been used for
low degree of hyperopia. In this technique, laser spots
are applied in a ring at the periphery to produce central
steepening. Regression effect and induced
astigmatism are the main problems.
2. Hyperopic PRK using excimer laser has also been
tried. Regression effect and prolonged epithelial
healing are the main problems encountered.
3. Hyperopic LASIK is effective in correcting
hypermetropia upto +4D.
4. Conductive keratoplasty (CK) is nonablative and
nonincisional procedure in which cornea is steepened
by collagen shrinkage through the radiofrequency
energy applied through a fine tip inserted into the
peripheral corneal stroma in a ring pattern. This
technique is effective for correcting hyperopia of upto
3D.