What Causes Poor Vision?

My Friend Bob is having visual problems it started in one eye now is in both eyes. He has been to a specialist and their is no retinal bleeding, the symptoms leading to this were slow to adjust washed out vision then he could focus on objects at a distance , this would occur during a bright day, also he lost the ability to read due to contrast issues he must use very bright light. He also cannot drive on bright days, he has diabeties, this on set of vison changes happend suddnely.