|MadSci Network: Medicine|
Since I do not know your educational background or age, I will try to answer this question as simply as I can.
Diabetes, as you may know, is a very important disease for the eyecare practioner because of the risk of diabetic retinopathy. There are several stages or classifications of diabetic retinopathy that can range from not affecting vision at all, to a vision threatening situation where surgical intervention is necessary to preserve vision. So in answer to your question, yes, diabetes can affect color vision. Usually, only in the severe forms of the disease, in which one's overall sensitivity to light is decreased, is color vision markedly decreased. It is harder to descriminate colors the more desensitized the retina is to light. Diabetic retinopathy is a small vessel disease, affecting the ability of the vessels to perfuse the retina with blood. In the elderly, color vision is also affected by age related optic atrophies, pupillary miosis (which decreases amount of light entering the eye), and age related lens changes.
The lens yellows as people age, therefore decreasing the amount of blue light reaching the retina. Blue-green distinction in the elderly is then impaired somewhat. Some poorly controlled diabetics can acquire diabetic cataracts that further impair color vision. Cataracts cause decreased contrast sensitivity by scattering incoming light. This effect decreases retinal illuminance, causes glare, and decreases visual acuity.
I hope this helps, good luck!
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