I don't think it will reverse the blindness. Dia-IonX helps more so in prevention rather than reversing damage already done. I would use Dia-IonX to improve regulation and reduce the rate of formation of other diabetic complications. You could ask your veterinarian about OcluVet eye drops. They were available quite a few years ago and were to diminish the formation of diabetic cataracts.
In addition I would give your dog Canine probiotics, Omega 3,6,9, MSM, and digestive enzymes. We carry the first two and the others can be found at a health food store.
These can support general health. Hope you can improve the quality of life for your dog.