A conjuctival cyst is a small, water-filled, sac that is growing on the conjuntiva of the eye. This type of cyst can be caused by a blocked duct, or by a small fold in the conjunctiva. Symptoms of a conjunctival cyst are trouble closing your eye or feeling that there is something in your eye. If you are experiencing these symptoms it is best to have your eyes examined by a doctor to rule out anything more serious. These kinds of cysts are easily treated with eye drops or ointments.