Cataracts are the usual cause. I think they are caused by low oxygen getting to the eye's....you will need to look that one up. If it is a temparary condition it is cause by low blood sugar. For years I had this problem and still do from time to time. I have low blood sugar naturaly so I foloow a diabetic diet to even out my blood sugar. When my eye gets like that, I know I need to eat something sweet ( fruit) and that resolves the problem. What you don't want is having to do that all day long. Eat healthy choices all day and you will not have that issue. I say this, but also note if you have blood sugar issues you might need to look at the medications your taking as well.
Hello,
there are many possible reasons ranging from age-related vision changes, to infection to cataracts, to diabetes, among many others.
However whatever the cause is the best possible outcome will only be achieved with early and aggressive medical treatment.
Please do go see a doctor immediately to get this addressed.
Best wishes