The sexually transmitted bacteria Chlamydia can cause conjunctivitis. It’s usually spread there by somebody who already has it on their genitals, & touches their eye. It can also be transmitted during oral sex if your eye comes in contact with your partner’s secretions. It’s not very common, and not so dangerous.
Conjunctivitis is infection or irritation of the conjunctiva, the clear membrane that covers the sclera (our firm, leathery eyeball) (see Diagram – The Eye). All types of conjunctivitis cause itching and tearing, not pain (which would suggest more serious eye disease). We might suspect Chlamydia as a cause if we see a cobblestone-like pattern of redness on the inside of the lower eyelid (see picture below). Then, we’d ask about sex life, though there may not be any genital symptoms. Diagnosis is made by a test for chlamydia.
There’s another type of Chlamydia eye infection called Trachoma, that plagues children in poor countries, and is the world’s leading cause of blindness. But it’s not present in the U.S.
Follicles on Lower Eyelid in Chlamydial Conjunctivitis