Pterygium is a wing-shaped fold of conjunctiva encroaching upon the cornea from either side within the interpalpebral fissure. The cornea is the clear front covering of the eye. This benign or noncancerous growth is often shaped like a wedge. It usually doesn’t cause problems or require treatment, but it can be removed if it interferes with your vision.
Etiology of Pterygium
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.
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.
- Age: Usually seen in old age.
- Sex: More common in males doing outdoor work than females.
- Laterality: It may be unilateral or bilateral. Usually present on the nasal side but may also occur on the temporal side.
Symptoms of Pterygium
- Cosmetic intolerance may be the only issue in otherwise asymptomatic condition in early stages. Foreign body sensation and irritation may be experienced.
- Defective vision occurs when it encroaches the pupillary area or due to corneal astigmatism induced by fibrosis in the regressive stage.
- Diplopia may occur occasionally due to limitation of ocular movements.
- Pterygium presents as a triangular fold of conjunctiva encroaching on the cornea in the area of palpebral aperture usually on the nasal side (Fig. 5.32) but may also occur on the temporal side. Very rarely, both nasal and temporal sides are involved (primary double pterygium).
Parts of a fully developed pterigium are as follows:
- Head: Apical part present on the cornea.
- Neck: Constricted part present in the limbal area, and
- Body: Scleral part, extending between limbus and the canthus.
- Cap: Semilunar whitish infiltrate present just in front of the head.
Types of pterygyum
Depending upon the progression it may be progressive or regressive pterigium.
It is thick, fleshy and vascular with a few whitish infiltrates in the cornea, infront of the head of the pterygium known as Fuch’s spots or islets of Vogt also called cap of pterygium.
It is thin, atrophic, attenuated with very little vascularity. There is no cap, but deposition of iron (Stocker’s line) may be seen sometimes, just anterior to the head of pterygium. Ultimately, it becomes membranous but never disappears.
- Cystic degeneration and infection are infrequent.
- Neoplastic change to epithelium, fibrosarcoma or malignant melanoma, may occur rarely.
Pterigyum must be differentiated from pseudopterygium. Psuedopterygium 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
|Etiology||Degenerative Process||Inflamatory Process|
|Age||Usually occurs in elderly persons||Can occur at any age|
|Sites||Always situated in the palpebral aperture||Can occur at any site|
|Stages||Either Progressive, regressive or Stationary||Always Stationary|
|Probe Test||Probe cannot be passed underneath||A probe can be passed under the neck|
Surgical excision is the only satisfactory treatment, which may be indicated for:
- Cosmetic disfigurement
- Visual impairment due to significant regular or irregular astigmatism.
- Continued progression threatening to encroach onto the pupillary area (once this has encroached pupillary area, wait till it crosses on the other side).
- 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:
- Surgical excision with free conjunctival limbal autograft(CLAU) taken from the same eye or other eye is presently the preferred technique.
- Also, Surgical excision with amniotic membrane graft and mitomycin-C MMC) (0.02%) application may be required in recurrent pterygium or when dealing with a very large one.
- Surgical excision with lamellar keratectomy and lamellar keratoplasty may be required in deeply infiltrating recurrent recalcitrant pterygia.
- Old methods to prevent recurrence (not preferred now) included transplantation of pterygium in the lower fornix (McRaynold’s operation) and postoperative use of beta irradiations.
Surgical technique of pterygium excision
- After topical anaesthesia, eye is cleansed, drap and exposed using universal eye speculum.
- Head of the pterygium is lifted and dissected the cornea very meticulously.
- Main mass of pterygium is then separated fro the sclera underneath and the conjunctiv superficially.
- This tissue is then excised taking care not damage the underlying medial rectus muscle.
- Haemostasis is achieved and the episcleral tissue exposed is cauterised thoroughly.
- Conjunctival limbal autograft (CLAU) transplant ation to cover the defect after pterygium excision. It is the latest and most effective technique in the management of pterygium. Use of fibrin glue to stick the autograft in place reduce operating time as well as discomfort associated with the sutures.