I have eye issues temparary blindness.?

about ten years ago. I was in a pool when i opened my eyes. The only thing i could see was a black ring going to gray. Kinda like tunnel vision. well it didnt happen again till last november. All a sudden my breathing got bad. So i went to the doc. I was told i have diabetes. plus my liver and thiroid was failing. Blood pressure and cholesterol was extremly high. well i started getting eye issues. just the lower half of my vision was distorted. I went to an eye specalist for people with diabetes. he did every test and found nothing. well i lost 70 pounds since then. I exercise regularly. there are no signs of diabetes effects no more. Although i still have it. but some days my eyes get blurry on the bottom half only. and the bouts of blindness are more frequent. But yet all my other problems are in check. well since i went to the eye doc. And he is special for diabetes. He had to of checked for gloucoma and nerve pressure. seeing that is diabetes norm. Well my vision was blurry when he looked directly in my eyes. but yet nothing. I've talked to my doc and he keeps saying i need gles. yet wouldnt all my vision be screwed not just the bottom. he gave me two eye exams and it was 20/25. has anyone have an idea what this is. I really would appreciate some good advice. Thank you have a great day.