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How Sunlight Damages The Eyes

Although the eyelid is designed to protect the eye, its skin is exceedingly thin and contains many fragile tissues that may be injured by UV light. Inside the eye, the lens and the cornea, both transparent, filter UV rays, but by doing so for many years, they may become damaged. This is especially true for the lens, which through years of UV absorption, turns yellowish and cataractous. The lens is the eye’s transparent focusing mechanism, located between the iris and the vitreous humor (the clear, thick gel in the posterior compartment of the eye that fills the space between the lens and retina, giving the eye its form and shape). The cornea, the transparent area in front at the outer layer of the eye, admits light and images to the retina. UV damage is instrumental in causing:

Eyelid cancers: Skin cancers of the eyelid, including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) as well as melanoma, account for 5 to 10 percent of all skin cancers. Most occur on the lower lid, which receives the most sun exposure. Basal cell carcinomas make up about 90 percent and squamous cell carcinomas 5 percent or more of all eyelid cancers, while melanomas account for about 1-2 percent. basal cell carcinomas of the eyelid affect an estimated 16.9 men and 12.4 women per 100,000 people in the U.S. each year, and while basal cell carcinomas elsewhere on the body rarely spread, eyelid basal cell carcinomas have a significant risk of spreading to the eye itself and surrounding areas, causing major damage to the eye and disfigurement to the face.

Squamous cell carcinomas have a faster growth rate and a greater potential to spread. Both of these types of cancer are found mainly in patients with a history of sun exposure. Melanoma can spread rapidly in the eye area and can prove lethal if not treated promptly. Melanomas have been linked to a history of intense, intermittent sun exposure and sunburns.

When diagnosed and treated early, eyelid cancers usually respond well to surgery and follow-up care, with the eye and eyelid largely retaining normal function. With reconstruction, they generally remain cosmetically attractive. But left untreated, they are extremely dangerous and may even ultimately penetrate the brain. Watch for these early warning signs:

If you have any of these warning signals, consult a skin cancer specialist or ophthalmologist, even if you feel no discomfort.

Intraocular melanoma: Although rare, it is the most common eye cancer in adults. It starts in the uveal tract, the middle layer of the eye containing the iris (the part of the eye responsible for eye color) and the pupil, which lies in the center of the iris. Symptoms may include a dark spot on the iris, blurred vision, or a change in the pupil’s shape. Sometimes, however, there are no symptoms.

Conjunctival cancers: Once rare, these cancers have been rising rapidly in incidence in recent years, based on NCI data. Research covering 10 percent of the U.S. population showed that incidence among white men especially increased – 295 percent over a 27-year period.

Conjunctival melanomas may be more common in patients with atypical mole syndrome; these patients have 100 or more moles, one or more moles 8 mm (1/3 inch) or larger in diameter, and one or more moles that are atypical. All patients with cutaneous melanomas and/or atypical moles should have yearly ophthalmologic evaluations.

Cataracts: A progressive clouding and yellowing of the crystalline lens, the eye’s focusing mechanism. At least 10 percent of cataract cases are directly attributable to UV exposure. In the U.S. alone, more than one million operations to remove cataracts are performed every year. Cataracts are the most common cause of treatable blindness worldwide, and UVB has been directly linked to cataracts.

Macular degeneration: Often referred to as age-related, or senile, macular degeneration, it is caused by damage to the retina over time. The retina is the ocular membrane where images are formed and transmitted to the brain; the macula, the region of sharpest vision near the center of the retina, is the most likely area to be damaged. Macular degeneration is one of the major causes of vision loss in the U.S. for people over age 60. While further research is required, some studies point to UVA and HEV light as potential causes of macular degeneration.

Benign growths of the conjunctiva: Problems with the conjunctiva, the protective membrane covering the outside of the eye and the inside of the eyelids, usually develop later in life. Pterygia, fleshy benign growths on the conjunctiva that may ultimately interfere with vision, may require surgical removal. These unsightly growths most frequently occur in areas where UV is intense year-round.

Keratitis, or corneal sunburnExcessive exposure to UV from the sun or tanning machines can literally burn the cornea, the eye’s clear refracting surface that admits light and images to the retina. UV-protective lenses are therefore especially a must for anyone who uses a tanning machine, as well as for skiers or snowboarders, since UV is more intense at high altitudes, and since snow reflects back the sun’s rays, so that they hit your eyes a second time.

Virtually all of these UV-related eye conditions can be found by an ophthalmologist during a routine eye exam. Thus, it is important to have a complete ophthalmologic exam, including dilated funduscopy, on a yearly basis.

Credits: https://www.skincancer.org/prevention/sun-protection/for-your-eyes/how-sunlight-damages-the-eyes

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