Blue Shield of California and an insurance company affiliate are encouraging vision plan members to buy eyeglasses that protect eyes against ultraviolet light.

California Blue, San Francisco, will provide up to $200 in benefits, with a $130 eyeglass frame allowance, for vision plan members who buy “photochromic” lenses, the company says.

Photochromic lenses become darker when exposed to UV light.

Studies have suggested that exposure to UV light might cause cataracts and other eye problems.