Diabetic Retinopathy:

Although diabetes does not necessarily lead to diabetic retinopathy, people with the diabetic retinopathy may experience a condition in which their diabetes causes blood vessels that feed the retina of the eye to break. The resulting damage may appear as spots or blanks in the field of vision. This condition is called Diabetic Retinopathy. In more severe cases of diabetic retinopathy, blood clots and scar tissue can develop on the retina, which can lead to complete vision loss. All people with diabetes should have regular eye exams and maintain good diabetic management. If diabetic retinopathy is detected, leaking vessels may sometimes be closed using a laser.

Typical reading solutions are desktop magnifiers.

Also See:
Age Related Macular Degeneration
Retinitis Pigmentosa