|
|
| |
SIGNS AND SYMPTOMS
In most cases, routine ocular evaluation reveals
pterygia in asymptomatic individuals or in patients
who present with cosmetic concern about a tissue
"growing over the eye." In some instances,
the vascularized pterygium may become red and inflamed,
motivating
the patient to seek immediate care. In other cases,
the irregular ocular surface can interfere with
the stability
of the precorneal tear film, creating a symptomatic
dry eye syndrome.
Rarely, the pterygium may induce irregular corneal
warpage, or even obscure the visual axis of the
eye,
resulting in diminished acuity.
Clinical inspection of pterygia reveals a raised,
whitish, triangular wedge of fibrovascular tissue,
whose base lies within the interpalpebral conjunctiva
and whose apex encroaches the cornea. The leading
edge of this tissue often displays a fine, reddish-brown
iron deposition line (Stocker's line). |
|
The vast majority of pterygia (about 90 percent) are located
nasally. These lesions are more commonly encountered in
warm, dry climates, or in patients who are chronically
exposed to outdoor elements or smoky/dusty environments.
PATHOPHYSIOLOGY
Ultraviolet light exposure (both UV-A and UV-B) appears
to be the most significant factor in the development of
pterygia. This may explain why the incidence is vastly
greater in populations near the equator and in persons
who spend a great deal of time outdoors. Other agents
that may contribute to the formation of pterygia include
allergens, noxious chemicals and irritants (e.g., wind,
dirt, dust, air pollution). Heredity may also be a factor.
Whatever the etiology, pterygia represent a degeneration
of the conjunctival stroma with replacement by thickened,
tortuous elastotic fibers. Activated fibroblasts in the
leading edge of the pterygium invade and fragment Bowman's
layer as well as a variable amount of the superficial
corneal stroma. Histologically, pterygium development
resembles actinic degeneration of the skin.
MANAGEMENT
Because pterygia appear to be linked to environmental
exposure, manage asymptomatic or mildly irritative cases
with UV-blocking spectacles and liberal ocular lubrication.
Advise patients to avoid smoky or dusty areas as much
as possible. Treat more inflamed or irritated pterygia
with topical decongestant/antihistamine combinations (e.g.,
Naphcon-A) and/or mild topical corticosteroids (e.g.,
FML, Vexol) four times daily in the affected eye.
• Surgical excision of pterygia is indicated only
for unacceptable cosmesis and/or significant encroachment
of the visual axis. The treatment of choice involves dissection
and removal of the fibrous tissue down to the level of
Tenon's capsule. Free conjunctival flaps are then grafted
over the bare sclera. Postoperative adjuvant therapy with
b-radiation, topical thiotepa, mitomycin-C and other antimetabolic
agents may diminish the chance of recurrence. In cases
that involve significant corneal scarring, lamellar or
penetrating keratoplasty may be indicated.
10% of recurrence rate is known after either surgical
approach.
|
|
