Most of the focusing power in the eye occurs along the front surface, called the cornea, which is the clear "window" in the front of the eyeball. The next structure involved in focussing is the lens, which sits behind the cornea inside the eye. The ideal cornea has a symmetrically curved surface, like a basketball. Astigmatism is caused by a cornea or a lens that is not symmetrical. As a result, people with significant astigmatism may have distorted or blurry vision.
Astigmatism is measured in...
Here's what you need to know about what sunglasses can do for you (apart from style) and how to choose them.
Eye on UV Risks
Just as the sun’s ultraviolet (UV) rays can damage skin, they can also harm the lens and cornea of the eyes.
UV radiation increases your odds of getting cataracts, which cloud the eye’s lens and lead to diminished eyesight. It has also been linked to macular degeneration, a treatable, but incurable disease of the macula, a part of the retina that is essential for sharp vision.
Other UV-related eye problems are pterygium and pingueculum. A pterygium occurs when the conjunctiva, the tissue that lays over the white of the eye, grows into the cornea. A pingueculum is a yellowish bump of tissue on the white of the eye.
Sunlight that bounces off highly reflective surfaces such as snow, water, sand, or pavement can be especially dangerous.
Photokeratitis is a corneal sunburn that’s also known as snow blindness. As the name suggests, skiers and snowboarders are particularly vulnerable to this temporary but acutely painful condition. “In photokeratitis, tiny blisters form on the surface of the cornea,” says Gail Royal, MD, an ophthalmologist in Myrtle Beach, S.C. “It’s a condition that will generally resolve on its own with proper medical treatment, but it’s uncomfortable enough to spoil your vacation.”
Sunglasses play a vital role in shielding the fragile tissue around the eye, says W. Lee Ball Jr., OD, an optometrist at Harvard Medical School’s Beth Israel Deaconess Medical Center. “This skin, including the eyelid itself, is very thin and vulnerable to skin cancer, and that’s especially troubling since dermatologists are reporting an epidemic in all types of skin cancer," Ball says.
Royal, who includes a review of proper sunglass use during patient visits, admits she sometimes appeals to her patients’ vanity.
“I’ll point out that sunglasses will protect not just against basal cell and squamous cell carcinomas and melanoma,” she says, “but also against the formation of wrinkles like crow’s feet and the unsightly thickening of the skin that can sometimes be caused by UV exposure.”