The association between chronic exposure to UVR and increased risk of cataract has been established by multiple large, long-term epidemiologic studies including the Chesapeake Bay Watermen Study, the Blue Mountains Eye Study, and the Beaver Dam Eye Study. Chronic exposure to UVR has also been implicated in other ocular disorders such as pinguecula, pterygium, Labrador keratopathy, and age-related macular degeneration (AMD). This means that minimizing chronic exposure to UVR is an important preventive strategy.
Potential for Retinal Exposure
UVR is to some extent absorbed by the ocular tissues (most UVB is absorbed by the cornea, and most UVA is absorbed by the crystalline lens). However, some UVA and UVB can still penetrate through to the back of the eye, making retinal damage a possibility. And although only small amounts of UVA and UVB reach the inner eye, the vulnerability of delicate ocular tissues to the damaging effects of UVR and the cumulative effects of exposure can make these amounts clinically important, representing yet another important reason to protect the eyes from chronic UVR exposure.
Acute Unprotected Exposure to UVR
Both acute and chronic UVR exposure presents a danger to the eye. It is important to differentiate the cumulative effects of long-term, but less intense, ocular UVR exposure from the immediate effects of acute, intense short-term exposure.
Acute, intense, unprotected exposure to UVR causes sunburn of the eyelids and surrounding skin and photokeratitis, a type of sunburn of the cornea. Snow blindness is one form of photokeratitis, as are the corneal “burns” seen after use of commercial tanning beds without ocular protection. Sunbathers, individuals monitoring sky or sea conditions, and laboratory workers exposed to UVR are also at risk. Arc welding is another potential source of acute exposure that can cause ocular damage. Another example of acute ocular pathology associated with short-term intense unprotected UVR exposure is solar retinopathy, most frequently associated with direct, unshielded viewing of solar eclipses.
UVR-Mediated Damage to the Eyelids
Acute intense unprotected solar UVR exposure produces sunburn of the eyelids. Because of their thin delicate structure, the eyelids are especially vulnerable to sunburn and are often not adequately protected by the topical sunblocks applied to the rest of the facial skin and the exposed body. Sunburn of the skin is usually due primarily to UVB and is characterized by painful redness, swelling, and occasional blistering and exfoliation of the affected eyelid skin.
The association between chronic solar UVR exposure and photoaging of the skin and cutaneous neoplasia is well-recognized. Photoaging, characterized by thickening and wrinkling of the skin, is primarily due to UVA exposure; the eyelids are a common site.
UVR-related skin cancer is a major health concern, with cutaneous neoplasia representing the most common form of cancer. Ten percent of all non-melanoma skin cancers (ie, basal and squamous cell carcinomas) occur on the eyelids; most of these are preventable with adequate ocular UVR protection or at least treatable if detected early.
Longer Lives Mean Increased Risk and Increased Need for Protection
The greater longevity that people are enjoying in the 21st century increases the total potential lifetime exposure to UVR. This, along with profound alterations in the protective ozone layer, has served to increase the risk of UVR-related ocular disease.