I did a search for diagnosis of some of my symptoms and came up with cataract. what do doctors look for to diagnose it?

Vision, observation: Your basic symptoms for a cataract is lowered vision with no other cause for the lowering. Cataracts are slow in onset and painless. A common early symptom is glare from oncoming headlights. When your ophthalmologist cannot improve eyeglasses to see well, then he will look for cataracts inside the eye with his instruments as a probable cause.