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I understand your concern.
The haziness as you have mentioned in history can be due to Diabetic Retinopathy, as you rightly pointed out or can also be due to cataract which invariably affects most human beings beyond 60 years. But since in hsitory you mentioned that he's diabetic for last 8 years, a possibility of diabetic retinopathy can't be ruled out. There can be other causes also like ARMD ( Age related macular degeration ). So i will advise you to get a second ophthalmologist opinion, who can dilate your fundus, examine the retina properly and run a test OCT( to rule out other complications of diabetes ). Have you noticed his eyes turning red, or is there any itching recently?
Diabetes also leads on to one more complication called macualr edema, which also leads to some loss of sight and can be really quick at times. So he does need a comprehensive eye examination. Kindly get it done as soon as possible.
If possible put up the reports once they are ready.
Do get back to us for additional queries.