Sunglasses are a healthy accessory to have along on a sunny summer day. They
reduce glare from the bright sunlight and also shield the eye from ultraviolet radiation and visible light.
The ultraviolet radiation from the sun may be related to eye conditions such as cataracts, pterygiums, pinguecula and skin cancers around the eyelid such as basal cell carcinoma, squamous cell carcinoma and melanoma.
Visible light (e.g. blue or violet) may also have a role in causing age related macular degeneration.
Sunglasses may not all be the same in terms of the amount of ultraviolet light they block out. The tint or color of the lens may also not be a good gauge when the tint is light or medium. In general, dark or very dark lenses block out more ultraviolet light but also visible light. Check if they comply to the American standard, European standard or Australian standard and you can determine the amount of protection they provide.
However, there are more considerations when choosing sunglasses. The size of the lens should not be too small. Also the fit of the frame should be such that it is not too distant from the forehead or light may leak in. Side shades or wrap around designs will also reduce light leakage.
Common colors of the sunglasses lens include gray, brown and green. These colours tend to not distort colors.
Sunglasses can also be made with prescriptions in built but these would tend to be expensive. An alternative would be to make photochromatic prescription glasses which change color when exposed to ultraviolet light. Be aware though that if you intend to also reduce glare while driving, photochromatic glasses will not change color as the windscreen glass will block out ultraviolet light. Sunglasses which clip on to existing glasses or fit over existing glasses are a cheap but good solution too.