My female red eyed tree frog got a cloudy patch on one of her eyes last year. I left it untreated for a while to see if it would get better but it just got progressively worse.

I first tried a week of preservative free eye drops nightly to clean it out. This didn't work.
Then I left her alone for a while before treating her for a week of nightly methylene blue drops in the eye. This did nothing but mess up the tank with blue stains!
Then I left her alone for a while again and now I have been treating her with Tetracycline drops for almost a week now and again see no improvement.

Her behavior hasn't changed she is very lively and always takes food.

Her other eye now has started to show a small amount of cloudiness, just how the bad one started out. I have 3 other red eyes in with her for years and they are all normal.

I am now thinking it could be either:
A cholesterol issue which I have heard can be caused by crickets as they are high in them? I'm not sure... I don't over feed her anyway, I always tong feed. She gets maybe 3-4 medium/large crickets a week if that sometimes less.
or it could just be old age as red eyes don't usually live longer than 5 years old. I have had her just over 4 years, she was fully grown when I got her and I have no idea how old she was then.

Here are some pictures, the bottom left pic is of her other eye that has now started to get cloudy too.