Pterygium (eye)
Template:Short description Template:For Template:Use dmy dates Template:Infobox medical condition (new) A pterygium of the eye (Template:Plural form: pterygia or pterygiums, also called surfer's eye) is a pinkish, roughly triangular tissue growth of the conjunctiva onto the cornea of the eye.<ref name=NEI2016/> It typically starts on the cornea near the nose.<ref name=Yan2009>Template:Cite book</ref> It may slowly grow but rarely grows so large that it covers the pupil and impairs vision.<ref name=NEI2016>Template:Cite web</ref> Often both eyes are involved.<ref name=Sm2005>Template:Cite book</ref>
The cause is unclear.<ref name=NEI2016/> It appears to be partly related to long term exposure to UV light and dust.<ref name=NEI2016/><ref name=Yan2009/> Genetic factors also appear to be involved.<ref name=Ang2014>Template:Cite journal</ref> It is a benign growth.<ref name=Hal2008>Template:Cite book</ref> Other conditions that can look similar include a pinguecula, tumor, or Terrien's marginal corneal degeneration.<ref name=Sm2005/>
Prevention may include wearing sunglasses and a hat if in an area with strong sunlight.<ref name=NEI2016/> Among those with the condition, an eye lubricant can help with symptoms.<ref name=NEI2016/> Surgical removal is typically only recommended if the ability to see is affected.<ref name=NEI2016/> Following surgery a pterygium may recur in around half of cases.<ref name=NEI2016/><ref name=Hal2008/>
The frequency of the condition varies from 1% to 33% in various regions of the world.<ref name=Dr2010/> It occurs more commonly among males than females and in people who live closer to the equator.<ref name=Dr2010/> The condition becomes more common with age.<ref name=Dr2010>Template:Cite journal</ref> The condition has been described since at least 1000 BC.<ref>Template:Cite journal</ref> Template:TOC limit
Signs and symptoms
Symptoms of pterygium include persistent redness,<ref name=Coroneo /> inflammation,<ref name=WillsEye4th>Template:Cite book</ref> foreign body sensation, tearing, dry and itchy eyes. In advanced cases the pterygium can affect vision<ref name=WillsEye4th /> as it invades the cornea with the potential of obscuring the optical center of the cornea and inducing astigmatism and corneal scarring.<ref>Template:Cite web</ref> 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.Template:Citation needed
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 (actinic elastosis<ref>Template:Cite book</ref>) 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 cornea, where they undergo refraction and become 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 (medial) side, however, the shadow of the nose medially reduces the intensity of sunlight focused on the lateral/temporal limbus.<ref name=Coroneo>Template:Cite journal</ref>
Some research also suggests a genetic predisposition due to an expression of vimentin, 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.<ref>Template:Cite web</ref> These cells also exhibit an increased P53 expression likely due to a deficit in the tumor suppressor gene. These indications give the impression of a migrating limbus because the cellular origin of the pterygium is actually initiated by the limbal epithelium.<ref>Template:Cite journal</ref>
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 is a practical test (technique) as the condition worsens.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>
Differential Diagnosis
Pterygium should be differentiated from pinguecula, which is histologically and etiologically similar to pterygium.<ref name="AAO">Template:Cite web</ref><ref name="Kanski">Template:Cite book</ref> 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.<ref name="Kanski" />
Prevention
As it is associated with excessive sun<ref>Template:Cite journal</ref> or wind exposure, 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. 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.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
Treatment
A pterygium typically does not require surgery unless it grows to such an extent that it causes visual problems.<ref name=NEI2016/> Some of the symptoms such as irritation can be addressed with artificial tears.<ref name=NEI2016/> Surgery may also be considered for unmanageable symptoms.<ref name=Mar2016>Template:Cite journal</ref>
Surgery
A Cochrane review found conjunctival autograft surgery was less likely to have reoccurrence of the pterygium at 6 months compared to amniotic membrane transplant.<ref name = Cle2016>Template:Cite journal</ref> More research is needed to determine which type of surgery resulted in better vision or quality of life.<ref name = Cle2016/> The additional use of mitomycin C is of unclear effect.<ref name = Cle2016/> Radiotherapy has also been used in an attempt to reduce the risk of recurrence.<ref>Template:Cite journal</ref>
Auto-grafting
Conjunctival auto-grafting is a surgical technique that is an effective and safe procedure for pterygium removal.<ref name=":0">Template:Cite book</ref> 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 attached 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 attached to the sclera using sutures, or glue adhesive.<ref>Template:Cite journal</ref><ref>Gulani AC. "Corneoplastique", Video Journal of Cataract and Refractive Surgery. Volume XXII. Issue 3, 2006.</ref><ref>Template:Cite journal</ref> Amniotic membrane by itself does not provide an acceptable recurrence rate.<ref>Template:Cite journal</ref>
References
External links
- Template:Commons-inline
- Pterygium eMedicine WebMD online article on pterygium (overview, differential diagnoses & workup, treatment & medication, and follow-up)