Hi Wendy,
As you mention in your question, the reason for blindness is the cataracts. When you do receive him I recommend that you have that confirmed. Next, determine if the cataracts are being caused by an underlying condition such as diabetes and if that is present then start treating it to slow the development of cataracts. I assume if he has received good medical care in the past such as routine blood work, then this would have already been found. Otherwise, I would assume these cataracts are congenital. If that is the case, then there are no supplements or vitamins that will prevent the issue. These treatments have not been shown to work for other ocular conditions either such as retinal degeneration; at least there are no documented studies that support the use of them.
There are a few treatments for cataracts that you can consider. I recommend you book an appointment with a veterinary ophthalmologist to discuss these options including the cost and prognosis. Removing the lens which is where the cataracts form is one of the more common procedures. As it turns out its the cornea, or top surface of the eye, which is responsible for most of the focusing power and so without the lens, a dog can live a life with very good sight.
If surgery is not an option due to expense, then there are not many choices left. However, you are correct, I have seen time and time again that when our pets lose their sight, they seem to have a very little decline in their quality of life. You mention deafness in your question and I can’t determine whether he is suffering from this or not by your description. If he is, it gives me a little more worry because dogs will rely on their other senses if one is deficient or absent. Not that he would use hearing to locate things around him, but it does allow for more simulation and therefore less reduction in quality of life, potentially. I still think the chances are that you will see that he retains a good quality of life regardless. I want to mention as well, that this is not just a subjective opinion I have. It is actually what has been objectively reported to me by owners of dogs who went blind and in fact, most of these owners had great difficulty believing me that quality of life will be insignificantly affected. They learned that what I said was true and came back to tell me that they had been worrying for nothing. That’s truly how I’m able to give this advice and it was consistent in every single case I witnessed throughout my career.
I hope this information helps. Good for you for going through with the adoption regardless. This is a lucky dog and I wish you and him the best.
Thanks and good luck.
Dr. Greenway