I have red eye more than 1 week without any help with antibiotic eye drops. what other underlying causes of red eye other than conjunctivitis?

Viral: Majority of pink eyes or conjunctivitis are viral, therefore they have to run their course usually 10-14 days. Antibiotics alone won't make any difference. Antibiotics and mild steroids given under opththalmologists care can decrease the redness. But either way it will there for the full course of it. If only one eye is red then there are many more dx:, iritis, foreign body, to name a couple.

Many things: Red eyes can be from inflammation from chronic allergies, dry eye syndrome, blepharitis (minor infection of the eyelid margin), meibomianitis (blocked ducts on eyelid margin. In addition, you may have inflammation on the top of the eye, episcleritis or scleritis or in the front to the eye, irtis. You need the right diagnosis to get the treatment to get rid of red eyes. You need eye exam.