A pterygium is a triangular, wing shaped, fibrovascular subepithelial ingrowth of degenerative bulbar conjunctival tissue over the limbus onto the cornea ( pterygos - “wing”)
It is a degenerative condition of subconjunctival tissues which proliferate as a vascularized granulation tissue to invade the cornea, destroying the superficial layers of the stroma and Bowman’s membrane, the whole being covered by conjunctival epithelium
It is loosely adherent in its whole length to the underlying sclera, the area of adherence being always smaller than its breadth, so that there are folds at the upper and lower borders .
- it is a fibrovascular proliferation of conj tissue onto cornea
- it is hyperplasia, not dysplasia
- stains with elastic tissue stains, but unlike elastic tissue, it is not digested by elastase, hence termed elastotic degeneration.
- body of pterygium incorporates the underlying Tenon’s capsule, but not the episclera, hence it can be easily mobilized over the sclera
- at the limbus – no Tenon’s – hence adherent to episclera
- Head of the pterygium grows in a plane between Bowman’s layer and the basement membrane of corneal epithelium – Bowman’s membrane initially pushed posteriorly – later gets destroyed and pterygium tissue grows into stroma – pterygium becomes firmly adherent.
- primary pterygium are histopathologically different from recurrent pterygium : Recurrent pterygium is composed of only fibrovascular tissue, no elastotic degeneration, involves underlying episclera, sclera, rectus muscle sheath and corneal stroma and is firmly adherent to underlying structures throughout its extent, is highly vascularized.
A small, grey, corneal opacity develops, near the nasal limbus.
The conjunctiva overgrows the opacity and progressively encroaches onto the cornea in a triangular fashion.
Anatomically divided into : head, neck and tail.
Head – part on the cornea
Neck – at the limbus
Tail – part on the sclera
A deposit of iron (Stocker line) may be seen in the corneal epithelium anterior to the advancing head of the pterygium in slow growing pterygiums, due to pooling of tears at the leading edge of pterygium
A probe can be slipped under the upper and lower folded borders of the body of the pterygium for a short extent and not across the entire breadth.
- surgical dissection of the pterygium starting from the head of the pterygium with lamellar keratectomy and extending to remove the body of the pterygium. The head, neck and body of pterygium are removed in one piece, leaving behind bare scleral area slightly more than the body of the removed pterygium. Hemostasis achieved using thermal cautery
Adhesion of the conjunctiva to the peripheral cornea due to inflammatory causes, always stationary.
May occur on any quadrant of the cornea, at any age
Lacks firm adhesion throughout the underlying structures, and occasionally has a broad leading edge on the corneal surface, a probe can be passed under the neck
These findings differentiate it from true pterygium.
Pseudopterygium may result from a peripheral corneal ulcer and ocular surface inflammation such as cicatrizing conjunctivitis, chemical burns, or may also occur secondary to chronic mechanical irritation from contact lens movement associated with inadequate lubrication of the corneal surface.
- fibrofatty tumours are congenital tumors consisting of fibrous tissue and fat, are not encapsulated
- more common in children
- signs : soft, movable, subconjunctival mass most commonly located at outer canthus
- treatment : should be avoided as surgery may be complicated by scarring, ptosis, dry eye and ocular motility problems. However, if they are particularly unsightly, then debulking the anterior portion.