Oh I know that full well and when I brought a rather nice and expensive pair of eyeglasses back in 2015 from Lenscrafters they had me looking into a machine that took a blood vessel map of my eyes. The map showed some damage to my eyes, but I was if I control my diet properly that the damage can be reversed.Actually that is one of those it depends situations. When a diabetic condition manifests the extended period of high blood sugar levels causes the lense of the eye to swell reshaping the lense and making everything blurry. That is usually not permanent and will go back to normal over time once the diabetic has their sugar levels under control. That said there is a second avenue for damaged vision caused by diabetes. When you are diabetic it weakens your blood vessels. Your eyes have thousands of very tiny blood vessels all through them. Sometimes the weakening causes the blood vessels to burst. Usually requires a laser procedure to cauterize the bleed. Everytime that happens you get a blind spot at the site of the bleed. Enough of them and you can be declared legally blind. Yes I am a type 2 diabetic and have personally experienced the first example. I have a close relative who is a type 1 diabetic and while not legally blind he does have significant vision loss because of the second example. I have to undergo a procedure every year to check for bleeds in my eyes.
The last a eye doctor examined my vision he did said he could tell my diabetes is well controlled.