An interesting fact is that iris color is actually the result of the amount or density of pigment cells in the iris. Pigment cells, called melanocytes, produce the pigment known as melanin. The amount and density of the 
melanin determines what colors of light are absorbed and what is reflected. In essence, the higher the concentration of melanin in the iris, the darker the iris color. But how does this affect vision or eye health?
The color of the iris does not affect visual acuity or the sharpness of a person’s vision. But, the amount of pigment can affect visual “comfort” in certain situations. For example, people with blue or light-green eyes may be more sensitive or experience more visual discomfort in bright sunny conditions than people with brown-colored eyes. This is because the higher concentration of melanocytes in the darker iris acts as a internal-sun shade of sorts. Light-colored eyes don’t have such a luxury. While everybody should have a quality pair of sunglasses, this becomes almost a requirement for those with light-colored eyes in order to increase visual comfort in sunny conditions.
The same type of action may explain how light colored irises may be associated with higher risks for certain eye problems. Since there is less of a filtering effect in the light-colored iris, more harmful UV light will pass through the iris and this may increase risks for cataracts and macular degeneration. Some studies have shown a higher incidence of these ocular conditions in patients with lighter-colored irises. Of course, this doesn’t mean that everyone with blue-colored eyes will get macular degeneration and early-onset cataracts, but it is something to consider in terms of increased risk factors. Yet, wearing sunglasses with UV-blocking lenses can reduce these risk factors and help all eyes stay healthy over the long haul.
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Best wishes,
Dr. Beach.