What is eye discharge? Eye discharge, or "sleep" in your eyes, is a combination of mucus, oil, skin cells and other debris that accumulates in the corner of your eye while you sleep. It can be wet and sticky or dry and crusty, depending on how much of the liquid in the discharge has evaporated. Other slang terms used to describe eye discharge include eye mattering, eye boogers, eye gunk, eye pus and goopy eyes. Sometimes called "rheum," eye discharge has a protective function, removing waste products and potentially harmful debris from the tear film and the front surface of your eyes. Your eyes produce mucus throughout the day, but a continuous thin film of tears bathes your eyes when you blink, flushing out the rheum before it hardens in your eyes. When you're asleep — and not blinking — eye discharge collects and crusts in the corners of your eyes and sometimes along the lash line, hence the term "sleep" in your eyes. Some sleep in your eyes upon waking is normal, but excessive eye discharge, especially if it's green or yellow in color and accompanied by blurry vision, light sensitivity or eye pain, can indicate a serious eye infection or eye disease and should be promptly examined by your eye doctor. Got gunk in your eye? Eye discharge is most likely nothing to worry about. But if it's sudden or excessive and you're concerned, book an appointment with an eye doctor today. It could merely be allergies or dry eyes. But it could also be conjunctivitis (pink eye) or some other type of infection. An eye doctor can help you discern what's causing that gunk... and help you get rid of it. Where does eye mucus come from? Eye discharge (rheum) is a function of your tear film and a necessary component of good eye health. It primarily consists of thin, watery mucus produced by the conjunctiva (called mucin), and meibum — an oily substance secreted by the meibomian glands which helps keep your eyes lubricated between blinks. Causes of eye discharge Sleep in your eyes usually isn't cause for alarm, but if you notice a difference in consistency, color and quantity of eye gunk, it could indicate an eye infection or disease. Common eye conditions associated with abnormal eye discharge include: Conjunctivitis Eye discharge is a common symptom of conjunctivitis (pink eye), an inflammation of the conjunctiva — the thin membrane that lines the "white" of the eye (sclera) and the inner surface of the eyelids. Thick, yellow eye discharge can be caused by an eye infection. In addition to itchy, gritty, irritated and red eyes, conjunctivitis typically is accompanied by white, yellow or green eye mucus which can form a crust along the lash line while you sleep. In some cases, eyelid crusting can be so severe that it temporarily seals your eye shut. There are three types of pink eye: viral, bacterial and allergic. Viral conjunctivitis is highly contagious and is caused by a virus such as the common cold or herpes simplex virus. Eye discharge associated with viral pink eye typically is clear and watery but may include a white or light-yellow mucus component. Bacterial conjunctivitis, as the name indicates, is caused by bacterial infection and can be sight-threatening if not treated promptly. Eye discharge is usually thicker and more pus-like (purulent) in consistency than viral pink eye, and is commonly yellow, green or even gray. Often, the sticky mattering will cause your eyelids to feel completely glued shut upon waking in the morning. Allergic conjunctivitis is triggered by allergens — pollen, dander, dust and other common irritants that cause eye allergies. It also can be caused by an allergic reaction to chemical pollutants, makeup, contact lens solutions, and eye drops. Eye discharge associated with allergic conjunctivitis is typically watery. Unlike viral and bacterial pink eye, allergic conjunctivitis is not contagious and always affects both eyes.