Pterygium

Pterygium (L. Pterygion = a wing) is a wing-shaped
fold of conjunctiva encroaching upon the cornea from
either side within the interpalpebral fissure.
Etiology. Etiology of pterygium is not definitely
known. But the disease is more common in people
living in hot climates. Therefore, the most accepted
view is that it is a response to prolonged effect of
environmental factors such as exposure to sun
(ultraviolet rays), dry heat, high wind and abundance
of dust.
Pathology. Pathologically pterygium is a
degenerative and hyperplastic condition of
conjunctiva. The subconjunctival tissue undergoes
elastotic degeneration and proliferates as
vascularised granulation tissue under the epithelium,
which ultimately encroaches the cornea. The corneal
epithelium, Bowman's layer and superficial stroma are
destroyed.
Clinical features. Pterygium is more common in
elderly males doing outdoor work. It may be unilateral
or bilateral. It presents as a triangular fold of
conjunctiva encroaching the cornea in the area of
palpebral aperture, usually on the nasal side (Fig.4.28),
but may also occur on the temporal side. Deposition of
iron seen sometimes in corneal epithelium anterior to
advancing head of pterygium is called stocker's line.
Parts. A fully developed pterygium consists of three
parts (Fig.4.28):
i. Head (apical part present on the cornea),
ii. Neck (limbal part), and
iii. Body (scleral part) extending between limbus and
the canthus.

Types. Depending upon the progression it may be
progressive or regressive pterygium.
Progressive pterygium is thick, fleshy and
vascular with a few infiltrates in the cornea, in
front of the head of the pterygium (called cap of
pterygium).
Regressive pterygium is thin, atrophic, attenuated
with very little vascularity. There is no cap.
Ultimately it becomes membranous but never
disappears.
Symptoms. Pterygium is an asymptomatic condition
in the early stages, except for cosmetic intolerance.
Visual disturbances occur when it encroaches the
pupillary area or due to corneal astigmatism induced
due to fibrosis in the regressive stage. Occasionally
diplopia may occur due to limitation of ocular
movements.
Complications like cystic degeneration and infection
are infrequent. Rarely, neoplastic change to
epithelioma, fibrosarcoma or malignant melanoma,
may occur.
Differential diagnosis. Pterygium must be
differentiated from pseudopterygium. Pseudopterygium
is a fold of bulbar conjunctiva attached to
the cornea. It is formed due to adhesions of chemosed
bulbar conjunctiva to the marginal corneal ulcer. It
usually occurs following chemical burns of the eye.
Differences between pterygium and pseudopterygium
are given in Table 4.3.
Table 4.3. Differences between pterygium and
pseudopterygium
Pterygium Pseudopterygium
1. Etiology Degenerative Inflammatory
process process
2. Age Usually occurs Can occur at any
in elderly age
persons
3. Site Always situated Can occur at any
in the palpebral site
aperture
4. Stages Either progressive, Always stationary
ssive,
regressive or
stationary
5. Probe Probe cannot A probe can be
test be passed passed under the
underneath neck
Treatment. Surgical excision is the only satisfactory
treatment, which may be indicated for: (1) cosmetic
reasons, (2) continued progression threatening to
encroach onto the pupillary area (once the pterygium
has encroached pupillary area, wait till it crosses on
the other side), (3) diplopia due to interference in
ocular movements.
Recurrence of the pterygium after surgical excision
is the main problem (30-50%). However, it can be
reduced by any of the following measures:
1. Transplantation of pterygium in the lower fornix
(McReynold's operation) is not performed now.
2. Postoperative beta irradiations (not used now).
3. Postoperative use of antimitotic drugs such as
mitomycin-C or thiotepa.
4. Surgical excision with bare sclera.
5. Surgical excision with free conjunctival graft taken
from the same eye or other eye is presently the
preferred technique.
6. In recurrent recalcitrant pterygium, surgical
excision should be coupled with lamellar
keratectomy and lamellar keratoplasty.
Surgical technique of pterygium excision
1. After topical anaesthesia, eye is cleansed, draped
and exposed using universal eye speculum.
2. Head of the pterygium is lifted and dissected off
the cornea very meticulously (Fig. 4.29A).

3. The main mass of pterygium is then separated
from the sclera underneath and the conjunctiva
superficially.
4. Pterygium tissue is then excised taking care not
to damage the underlying medial rectus muscle
(Fig. 4.29B).
5. Haemostasis is achieved and the episcleral tissue
exposed is cauterised thoroughly.
6. Next step differs depending upon the technique
adopted as follows:
i. In simple excision the conjunctiva is sutured
back to cover the sclera (Fig. 4.29C).
ii. In bare sclera technique, some part of
conjunctiva is excised and its edges are
sutured to the underlying episcleral tissue
leaving some bare part of sclera near the
limbus (Fig. 4.29D).
iii. Free conjunctival membrane graft may be
used to cover the bare sclera (Fig. 4.29E).
This procedure is more effective in reducing
recurrence. Free conjunctiva from the same
or opposite eye may be used as a graft.
iv. Limbal conjunctival autograft transplantation
(LLAT) to cover the defet after
pterygium excision is the latest and most
effective technique in the management of
pterygium.