Other important ocular conditions that impact Healthy Sight include pterygium and pinguecula, tumors of the eyelid and conjunctiva. Low vision, which can arise as a result of many ocular conditions, is also an important consideration for the Healthy Sight Counselor.
Pterygium
Pterygium is a chronic inflammatory disorder of the ocular surface characterized by the invasion and overgrowth of vascularized conjunctival tissue at the limbus, with gradual progression onto the corneal surface. This occurs as a 2-stage process that involves chronic inflammation, cellular proliferation, and connective tissue remodeling and angiogenesis, with the development of new blood vessels. Pterygia produce ocular problems in 2 ways: 1) because of their vascularity and elevated irregular surface consistency, they tend to produce ocular surface drying and irritation and can cause an unsightly local hyperemia; and 2) pterygia can adversely affect vision, either directly when they grow to extend into the visual axis, or indirectly by inducing a mechanical corneal astigmatism.
Mild pterygia can be treated symptomatically with topical lubricants and decongestants. More severe pterygia that compromise vision require surgical excision, although recurrences postoperatively are not uncommon. Undoubtedly the best treatment for pterygia is prevention.
Pterygia are most commonly seen at the nasal limbus. (Temporal pterygia do occur, but are almost always in accompaniment of—and less extensive than—nasal pterygia.) An interesting mechanism has been proposed to explain this preferential distribution wherein peripheral light directed at the temporal limbus is deflected by the anterior portion of the eye, resulting in a focus of light that is 20-fold greater in intensity at the nasal limbus. The intensity of this focus depends on the shape of the cornea and the depth of the anterior chamber of the eye.
There is a strong relationship between the development of pterygia and geographic/environmental factors. Pterygia are most commonly seen in individuals of darker complexion who spend considerable time outdoors. Multiple epidemiologic studies have strongly linked chronic UVR exposure to pterygia. For example, among indigenous people of the upper Amazon basin where exposure to UVR is high, pterygia are much more common in those who reside riverside than in forest dwellers. The Chesapeake Bay Watermen Study is a key source of data on exposure to sunlight and long-term ocular health in which the authors reported a higher prevalence of pterygia and climatic droplet keratopathy in people with histories of higher exposure to blue or visible light.
Risk Factors for Pterygium
Risk factors for pterygia include the following:
- Increased exposure to UVR, particularly in subtropical and tropical climates
- Engaging in occupations requiring extensive time spent outdoors (eg, farmers, fishermen, construction workers)
In addition, a genetic predisposition to the development of pterygia appears to exist in certain families. Males are affected more frequently than females, although this finding may reflect the greater time they spend outdoors with increased exposure to solar radiation.