Welcome to question of the day #359

 Eyetools question of the day #359

I am an eye care specialist working in community practice. I know that UV light is part of the process that forms cataracts and some of my colleagues advise patients with early cataracts to have photochromic spectacle lenses to slow down the cataract development process. Do photochromic lenses slow down the cataract development process?

UV light causes proteins inside lens cells show to clump together over time. , The clumped proteins scatter light rather than transmit it to the retina. The neat order of proteins inside the lens is disrupted and a cataract forms.

Therefore keeping UV out of the eye (and off the front surface of the eye and lid margins) will slow the cataract formation process and prevent corneal damage and lid margin cancer.

Most UV is absorbed by the cornea and the lens. Some does get through to the retina and there is a suggestion that UV might be part of the age-related macular degeneration process. UV consists of light of short-wavelengths and the shorter the wavelength the more potential for damage to human tissue.

Standard lenses do absorb UV but only around 90% of the incident amount. Photochromic (and other lens types) absorb 100% of UV that is incident on the eye.

It is clinically appropriate to highlight the UV absorption benefits of photochromic lenses to all patients but particularly those who have early signs of cataract.