Diabetes can affect the eyes that can cause permanent loss of vision and blindness. Diabetic retinopathy is the most common cause of vision loss in people with diabetes. The beginning stages of diabetic eye disease is usually unnoticed by most patients so regular check-ups are important and should be performed at least once a year.
Diabetes damages the small blood vessels of the eyes and can cause small bleeding in the eye (hemorrhages). It can also lead blood vessels to leak fluid (edema) and fat (hard exduates) in the retina (the retina is the tissue in the back of the eye that receives and processes the light that we see). When fluid and fat forms in the macula (the macula is the part of the retina that processes our central vision), there is vision loss and distortion which can be permanent. Fluid build up in the macula (macular edema) can be treated with injections in the eye with a special medicine (Anti-VEGF, ie Avastin) or laser treatment.
Long term damage to the blood vessels in the eye can cause a lack of oxygen to be delivered to the eye (ischemia) which can also cause permanent vision loss. Ischemia can also lead to new blood vessel growth in the eye (neovascularization). However, these new vessels are abnormal and can cause bleeding inside the eye (vitreous hemorrhage), glaucoma (elevated pressure in the eye causing nerve damage), and retinal detachment (when the retina comes off the back of the eye). Treatment of these abnormal vessels include injections with Anti-VEGF medications, laser, and surgery.
Finally, diabetes can accelerate cataracts in the eye. Cataracts are when the lens inside the eye becomes cloudy, causing glare and decreased vision. Cataracts can be cured with cataract surgery.
If you are diabetic and are having vision loss, it is important to visit your ophthalmologist for a check-up. You can read more about diabetic eye disease here