July 30, 2016
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Eyeglasses, Sunglasses, and Magnifiers (cont.)

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Sunglasses that can be purchased without a prescription come in hundreds of models with varying shapes, materials, coatings, configurations, and colors.

A must-have feature for all sunglasses is complete (100%) protection against the potentially damaging effects of the sun's ultraviolet A (UVA) and ultraviolet B (UVB) rays. Avoid buying dark sunglasses that do not offer 100% UV protection. Dark glasses prompt the pupil of the eye to dilate (enlarge), allowing UV rays to enter. So, if dark glasses lack complete UV protection, they can paradoxically promote damage to the eye.

Ultraviolet rays are well-known contributing causes of the following eye conditions:

Ultraviolet rays are well-known causes of the following eye conditions:

  • Macular degeneration is a potentially blinding condition in which the pigment cells in the optical center of the retina slowly degenerate during the dry form of this increasingly common disease, creating distorted vision. The rapidly changing form, or wet macular degeneration, can lead to sudden vision loss. Fortunately, remarkable new medications are now available to arrest and reverse damage caused by wet macular degeneration if caught in time.
  • Cataract is an extremely common condition in which the clear crystalline lens of the eye develops progressive clouding and opacity. People living at high altitudes, equatorial regions, and those with outdoor occupations generally develop cataracts at a younger age than others due to increased lifetime UV exposure.
  • Pterygium is a degenerative process on the ocular surface in which the normally clear mucous membrane, called the conjunctiva, overlying the white part of the eye, or sclera, gradually becomes cloudy and elevated, and then grows toward the center of the cornea. Advanced cases can lead to vision distortion and permanent loss of visual acuity. Once again, people from equatorial regions and those with outdoor occupations are much more likely to develop pterygium. Fishermen, farmers, sailors, surfers, construction workers, and sun worshippers are particularly susceptible.
  • Basal cell carcinoma is a slow growing superficial cancer in which abnormal skin cells turn cancerous, particularly on the lower eyelids, where there is more UV exposure than the upper eyelids. When detected early, basal cell carcinoma of the eyelid can be cured with surgical excision.
  • Squamous cell carcinoma is a more rapidly growing form of cancer in which abnormal conjunctival cells form a cancerous growth on the surface of the eyeball. This tumor type is more dangerous and invasive than the more common basal cell carcinoma, and it also benefits from early detection, surgical excision, and freezing or cryotherapy.

Some favorable features that consumers should be aware of include the following:

  • Polarization: Polarized sunglasses reduce glare from snow, water, highways, and other reflective surfaces. Consequently, wearers see better and squint less. These advantages can be crucial to automobile drivers, airline pilots, heavy-equipment operators, and athletes.
  • Impact resistance: Impact-resistant sunglasses resist breakage when dropped or mishandled. Glasses made of a trade-name plastic called CR-39 are lighter than glass and more impact-resistant. Glasses made of high-index plastic are even lighter than CR-39 glasses. In addition, these lenses have a coating that protects them against scratching.
  • Photochromicity: Photochromic sunglasses have lenses that brighten or darken in response to the intensity of sunlight. This transitional lens treatment does not in and of itself provide UV protection, a common misconception. Thus, be sure to look for the UV protection rating of photochromic lenses as a separate value.
  • Water-sheeting: Lenses with this feature help preserve visual acuity when water (from the rain, the sea, waterfalls, etc.) strikes the lens. With water-sheeting, the water forms in a see-through sheet on the lens rather than individual droplets that block or distort vision.
Medically Reviewed by a Doctor on 3/24/2016

Source: MedicineNet.com

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