Pterygium
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Roukoz A. Karam, M.D.[2]
Synonyms and keywords: pterygia
Overview
Pterygium usually refers to a benign growth of the conjunctiva. Alternately, it refers to any winglike triangular membrane occurring in the neck, eyelids, knees, elbows, ankles or digits. An example is popliteal pterygium syndrome, which affects the legs. The term comes from the Greek word pterygion meaning "wing".
When associated with the conjunctiva, a pterygium commonly grows from the nasal side of the sclera. It is associated with, and thought to be caused by ultraviolet-light exposure (e.g. sunlight), low humidity, and dust. The predominance of pterygia on the nasal side is possibly a result of the sun's rays passing laterally through the cornea where it undergoes refraction and becomes focused on the limbic area. Sunlight passes unobstructed from the lateral side of the eye, focusing on the medial limbus after passing through the cornea. On the contralateral side, however, the shadow of the nose medially reduces the intensity of sunlight focused on the lateral/temporal limbus.
Historical Perspective
Classification
Pathophysiology
- Pterygium in the conjunctiva is characterized by elastic degeneration of collagen and fibrovascular proliferation.
- It has an advancing portion called the head of the pterygium, which is connected to the main body of the pterygium by the neck.
- Sometimes a line of iron deposition can be seen adjacent to the head of the pterygium called Stocker's line.
- The location of the line can give an indication of the pattern of growth. As it is a benign growth, it requires no treatment unless it grows to such an extent that it covers the pupil, obstructing vision. Some patients may also choose surgery if the growth becomes too unsightly. The exact cause is unknown, but it is associated with excessive exposure to wind, sun, or sand. Wearing protective sunglasses with side shields and/or wide brimmed hats and using artificial tears throughout the day may help prevent their formation or stop further growth. For surfers and other water-sport athletes, they should wear eye protection that block 100% of the UV rays from the water.
Occasionally it is found as an incidental finding in middle aged patients who spend a lot of time in the sun. Pterygiums are also among younger men and women who surf, wakeboard, and kiteboard due to excessive exposure to UV rays bouncing off of the water. Skiiers and snowboarders protect their eyes on the snow so athletes participating in water sports also need to take heed of the UV rays and protect their eyes.
Causes
Differentiating Pterygium From Other Diseases
Epidemiology and Demographics
Age
Several population-based studies have found higher rates of pterygium to be associated with older age,
Gender
Race
Risk Factors
Screening
Natural History, Complications, and Prognosis
- The natural history of pterygium is poorly understood.
- Pterygium, when active, can grow over a period of several months to years.
- Activity is marked clinically by redness and localized thickening, which probably represent active inflammation. When inactive (white and flat), pterygium may remain static for decades with no measurable increase in size or clinical significance. It is unclear how pterygium converts from active to inactive, or if it can be reactivated.
Diagnosis
Diagnostic Study of Choice
- The diagnosis of pterygium is made by the classic clinical appearance of a wedge-shaped growth extending onto the cornea.
- However, pterygium does not always manifest in its classic form, and other conditions may have a similar appearance.
- It is important to distinguish pterygium from these other conditions, particularly neoplastic lesions.
History and Symptoms
- The most common symptoms caused by pterygium are redness and irritation.
- Visual impairment is less common. In the absence of symptoms, patients may also report a change in the appearance of their eye, or pterygium may be noted incidentally on physical examination.
Physical Examination
Laboratory Findings
Electrocardiogram
X-ray
Echocardiography or Ultrasound
CT scan
MRI
Other Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
While patients can be symptomatically treated with artificial tears, no reliable medical treatment exists to reduce or even prevent pterygium progression.
Surgery
Definitive treatment is achieved only by surgical removal. Long term follow up is required as pterygium may recur even after complete surgical correction.
Indications for surgical removal of pterygium include:
- Astigmatism leading to visual impairment
- Opacity in the visual axis
- Documented growth that is threatening to affect the visual axis via astigmatism or opacity
- Restriction of eye movement
- Significant cosmetic impact or intractable irritation
Primary Prevention
- There are no established measures for the primary prevention of pterygium.
Secondary Prevention
See also
External links
- Facts About the Cornea and Corneal Disease The National Eye Institute (NEI)
References