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.1.), 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.1.):

i. Head (apical part present on the cornea),

ii. Neck (limbal part), and

iii. Body (scleral part) extending between limbus and

the canthus.

Fig.1.Pterygium