Pterygium: A Review
Dr Ramya Subramaniam, DNB
Dr Srinivas K Rao, DO, DNB, FRCSEd
Darshan Eye Clinic, Chennai
PTERYGIUM
A pterygium is a fibrovascular, wing-shaped encroachment of the conjunctiva onto the cornea, usually in the horizontal meridian of the palpebral fissure. Histopathology shows hyaline degeneration with elastotic proliferation.
RISK FACTORS
Exposure to ultraviolet light and environmental microtrauma to the ocular surface is thought to predispose to pterygium formation. A localized limbal stem cell dysfunction, possibly related to ultraviolet induced damage and a genetic predisposition has also been postulated.
PATHOGENESIS
Pterygium pathogenesis can be considered as occurring in two stages: the initial disruption of the limbal corneal-conjunctival epithelial barrier, and the progressive “conjunctivalization” of the cornea characterized by cellular proliferation, inflammation, connective tissue remodeling, and angiogenesis
MORPHOLOGY
Head—the part which rests on the cornea
Neck— constricted portion seen at the limbus
Body – remaining bulk of mass
Cap—a semilunar infiltrating portion in front of the head showing opaque spots (Fuch’s spots) suggestive of progression.
STAGES
A progressive pterygium is thick, fleshy and vascular showing the presence of opaque infiltrates ahead of the head of the pterygium. A atrophic pterygium is thin, with little vascularity. The presence of a pigment line in front of the pterygium commonly referred to as Stocker’s line is suggestive of long standing non-progressive pterygium. A classification of the stage of pterygium based on the visibility of the underlying episcleral structures has been proposed.
PRESENTATION
Patients may present with repeated episodes of redness, pain, and watering due to inflammation of the pterygium, or due to drop in vision caused by encroachment of the pterygia onto the pupillary axis or high astigmatism. Quite often though, it may be an incidental finding in an asymptomatic patient.
PTERYGIUM VS PSEUDOPTERYGIUM
A pseudopterygium is the result of corneal inflammation due to chemical burns, corneal perforation, or longstanding corneal ulcers, with the reparative process leading to the growth of the conjunctiva onto the cornea. It is differentiated from a true pterygium by the history of prior inflammation, presence in one eye, location other than the horizontal meridian, a configuration that does not resemble the “wing” structure of the true pterygium, non progressive nature, and the ability to pass a probe under the neck of the pterygium (in some cases).
WHAT TO LOOK FOR ?
- Position : nasal or temporal
- Laterality: true pterygia are usually bilateral as apposed to pseudopterygia.
- Progression: increased vascularity and fleshiness is usually seen in progressive pterygia as apposed to thinned out pale atrophic pterygia.
- Extent: of encroachment of the pterygia onto the cornea is required to predict outcome of intervention – especially with regard to vision recovery. The width of the pterygium at the limbus is also noted.
- Presence of subepithelial deposits ahead of the head of the pterygia is suggestive of progression.
- Presence of the Stocker’s line of pigmentation is suggestive of a long standing, non-progressive lesion.
- Restriction of movement is often seen in recurrent pterygia with conjunctival loss and scarring.
- Inflammation: the presence of conjunctival inflammation in the body of the pterygium should be noted.
- In patients, who have a recurrent pterygium after previous surgery the presence of corneal thinning that may affect the surgical procedure, must be noted.
- Similarly, if a conjunctival autograft is planned, the health of the bulbar conjunctiva, the presence of a glaucomatous bleb, and the possibility of future glaucoma risk in the patient, must be considered.
TREATMENT
The following are considered indications for the surgical treatment of a pterygium
- Encroachment upon the pupillary area causing visual disturbance.
- Recurrent inflammation.
- Definite evidence of progression like - absence of Stocker’s line, subepithelial deposits ahead of the pterygium head.
- Peripheral pterygium, but distortion of vision due to high astigmatism.
- Restriction of ocular movement, with diplopia
- Cosmetic reasons
- Rarely, for suspicion of metaplastic changes.
MEDICAL
Patients who are at high risk of the development of pterygia because of a positive family history of pterygia or because of extended exposure to ultraviolet irradiation need to be educated in the use of ultraviolet-blocking glasses and other means of reducing ocular exposure to ultraviolet light such as avoid direct sunlight,wear goggles, cap etc. The use of tear substitutes can be considered to minimize the effects of environmental microtrauma in those exposed to the same.
SURGICAL
1. Excision with simple closure of the wound.
2. Mc Gavics bare sclera method: where in the pterygia is excised and the conjunctival defect is left as it is.
3.Transplantation of the pterygia : done in recurrent pterygia/ large pterygia.
- Mac Reynold’s operation: head is sutured to the body itself
- Kehr’s operation: head is sutured to the inferior fornix
The bare sclera technique of pterygium excision was the preferred approach, until recently, owing to the simplicity of the procedure and short duration of surgery – often performed as an office procedure. Soon, however, came the realization, that the procedure resulted in unacceptably high rates of recurrence and granuloma formation – as high as 75 to 85% in some series. Hence, modifications of the procedure, described above, were introduced. Although these approaches increased the technical complexity of the procedure, the outcomes did not improve.
4. In order to reduce recurrence rates, the use of beta irradiation and thiotepa were considered to reduce the occurrence of the fibroblastic recurrence response.However the increased occurrence of scleral complications with these approaches, also reduced their applicability and these are also seldom in use today.
