A pterygium of the eye (plural ''pterygia'' or ''pterygiums'', also called surfer's eye) is a pinkish, roughly triangular tissue growth of the

conjunctiva The conjunctiva is a thin mucous membrane that lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of non-keratinized, stratified squamous epithelium with goblet cells, stratified columnar epitheliu ...

onto the

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical po ...

of the

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and con ...

. It typically starts on the cornea near the nose. It may slowly grow but rarely grows so large that it covers the

pupil The pupil is a black hole located in the center of the iris of the eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company. It appears black ...

and impairs vision. Often both eyes are involved. The cause is unclear. It appears to be partly related to long term exposure to

UV light Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiatio ...

and dust. Genetic factors also appear to be involved. It is a benign growth. Other conditions that can look similar include a pinguecula, tumor, or Terrien's marginal corneal degeneration. Prevention may include wearing sunglasses and a hat if in an area with strong sunlight. Among those with the condition, an eye lubricant can help with symptoms. Surgical removal is typically only recommended if the ability to see is affected. Following surgery a pterygium may recur in around half of cases. The frequency of the condition varies from 1% to 33% in various regions of the world. It occurs more commonly among males than females and in people who live closer to the equator. The condition becomes more common with age. The condition has been described since at least 1000 BC.

Signs and symptoms

Symptoms of pterygium include persistent redness, inflammation, foreign body sensation, tearing, dry and itchy eyes. In advanced cases the pterygium can affect vision as it invades the cornea with the potential of obscuring the optical center of the cornea and inducing astigmatism and corneal scarring. Many patients do complain of the cosmetic appearance of the eye either with some of the symptoms above or as their major complaint. The use of standard contact lenses can become uncomfortable or even impossible although custom shaping may improve the fit to some extent.

Cause

The exact cause is unknown, but it is associated with excessive exposure to wind, sunlight, or sand. Therefore, it is more likely to occur in populations that inhabit the areas near the equator, as well as windy locations. In addition, pterygia are twice as likely to occur in men than women.

Pathology

Pterygium in the conjunctiva is characterized by elastotic degeneration of

collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whol ...

(

actinic elastosis Actinic elastosis, also known as solar elastosis, is an accumulation of abnormal elastin (elastic tissue) in the dermis of the skin, or in the conjunctiva of the eye, which occurs as a result of the cumulative effects of prolonged and excessive su ...

) 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. The predominance of pterygia on the nasal side is possibly a result of peripheral light focusing, where the sun's rays passing laterally through the

, where they undergo refraction and become focused on the limbic area. Sunlight passes unobstructed from the

lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction * Lateral cricoarytenoid muscle * Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics * Lateral c ...

side of the eye, focusing on the medial limbus after passing through the cornea. On the

contralateral Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pr ...

(medial) side, however, the shadow of the nose medially reduces the intensity of sunlight focused on the

/ temporal

limbus Limbus (Lat. "edge, boundary") may refer to: * Corneal limbus, the border of the cornea and the sclera (the white of the eye) * Limbus of fossa ovalis, in the heart * Limbus 3 and Limbus 4, two line-ups of a German avant-garde musical group * L ...

. Some research also suggests a genetic predisposition due to an expression of

vimentin Vimentin is a structural protein that in humans is encoded by the ''VIM'' gene. Its name comes from the Latin ''vimentum'' which refers to an array of flexible rods. Vimentin is a type III intermediate filament (IF) protein that is express ...

, which indicates cellular migration by the keratoblasts embryological development, which are the cells that give rise to the layers of the cornea. Supporting this fact is the congenital pterygium, in which pterygium is seen in infants. These cells also exhibit an increased P53 expression likely due to a deficit in the

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

suppressor gene. These indications give the impression of a migrating

because the cellular origin of the pterygium is actually initiated by the limbal epithelium. The pterygium is composed of several segments: * Fuchs' Patches (minute gray blemishes that disperse near the pterygium head) * Stocker's Line (a brownish line composed of iron deposits) * Hood (fibrous nonvascular portion of the pterygium) * Head (apex of the pterygium, typically raised and highly vascular) * Body (fleshy elevated portion congested with tortuous vessels) * Superior Edge (upper edge of the triangular or wing-shaped portion of the pterygium) * Inferior Edge (lower edge of the triangular or wing-shaped portion of the pterygium).

Diagnosis

Pterygium (conjunctiva) can be diagnosed without need for a specific exam, however

corneal topography Corneal topography, also known as photokeratoscopy or videokeratography, is a non-invasive medical imaging technique for mapping the anterior curvature of the cornea, the outer structure of the eye. Since the cornea is normally responsible for so ...

is a practical test (technique) as the condition worsens.

Differential Diagnosis

Pterygium should be differentiated from pinguecula, which is histologically and etiologically similar to pterygium. Unlike pterygium, pinguecula is seen only on the conjunctiva, it will not progress to limbus or cornea. Another condition which is similar to pterygium is inflammatory adhesion of conjunctiva to cornea known as pseudopterygium. Unlike pterygium, it may occur anywhere around cornea and the adhesion is usually limited to its apex.

Prevention

As it is associated with excessive sun or wind exposure, wearing protective

sunglasses Sunglasses or sun glasses (informally called shades or sunnies; more names below) are a form of protective eyewear designed primarily to prevent bright sunlight and high-energy visible light from damaging or discomforting the eyes. They can so ...

with side shields and/or wide brimmed hats and using artificial tears throughout the day may help prevent their formation or stop further growth. Surfers and other water-sport athletes should wear eye protection that blocks 100% of the UV rays from the water, as is often used by snow-sport athletes. Many of those who are at greatest risk of pterygium from work or play sun exposure do not understand the importance of protection.

Treatment

A pterygium typically does not require surgery unless it grows to such an extent that it causes visual problems. Some of the symptoms such as irritation can be addressed with artificial tears. Surgery may also be considered for unmanageable symptoms.

Surgery

Pterygium removal surgery A

Cochrane review Cochrane (previously known as the Cochrane Collaboration) is a British international charitable organisation formed to organise medical research findings to facilitate evidence-based choices about health interventions involving health profess ...

found conjunctival autograft surgery was less likely to have reoccurrence of the pterygium at 6 months compared to amniotic membrane transplant. More research is needed to determine which type of surgery resulted in better vision or quality of life. The additional use of

mitomycin C Mitomycin C is a mitomycin that is used as a chemotherapeutic agent by virtue of its antitumour activity. Medical uses It is given intravenously to treat upper gastro-intestinal cancers (e.g. esophageal carcinoma), anal cancers, and breast c ...

is of unclear effect.

Radiotherapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Rad ...

has also been used in an attempt to reduce the risk of recurrence.

Auto-grafting

Conjunctival auto-grafting is a surgical technique that is an effective and safe procedure for pterygium removal. When the pterygium is removed, the tissue that covers the sclera known as the Tenons layer is also removed. Auto-grafting covers the bare sclera with conjunctival tissue that is surgically removed from an area of healthy conjunctiva. That "self-tissue" is then transplanted to the bare sclera and is fixated using sutures or tissue adhesive.

Amniotic membrane transplantation

Amniotic membrane transplantation is an effective and safe procedure for pterygium removal. Amniotic membrane transplantation offers practical alternative to conjunctival auto graft transplantation for extensive pterygium removal. Amniotic membrane transplantation is tissue that is acquired from the innermost layer of the human placenta and has been used to replace and heal damaged mucosal surfaces including successful reconstruction of the ocular surface. It has been used as a surgical material since the 1940s, and has been shown to have a strong anti-adhesive effect. Using an amniotic graft facilitates epithelialization, and has anti-inflammatory as well as surface rejuvenation properties. Amniotic membrane transplantation can also be fixated to the sclera using sutures, or glue adhesive. Amniotic membrane by itself does not provide an acceptable recurrence rate.

References

External links

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Pterygium
eMedicine WebMD online article on pterygium (overview, differential diagnoses & workup, treatment & medication, and follow-up) {{Eye pathology Disorders of conjunctiva Eye surgery Wikipedia medicine articles ready to translate Wikipedia neurology articles ready to translate