Yes, the eyes produce a form of mucus, and it is normal to find it collected around the corners, especially upon waking. This substance is commonly known as “sleep crust,” “eye gunk,” or medically, rheum. Rheum is the residue of the eye’s continuous self-cleaning process, combining protective secretions and debris. While awake, blinking washes this material away through the tear ducts. During sleep, however, the debris accumulates because there is no blinking action to flush it out. The presence of this discharge is typically a sign of a healthy eye maintaining its protective tear film.
Defining Eye Discharge: Function and Composition
Normal eye discharge is a mixture of substances from the tear film and debris cleared from the eye’s surface. A primary component is mucin, a thin, watery mucus produced by the conjunctiva, the clear membrane covering the white of the eye and the inner eyelid. Mucin acts as a sticky trap for foreign particles and provides lubrication.
Oil, known as meibum, is also incorporated into the discharge. It is secreted by the meibomian glands located along the eyelid margins. Meibum helps prevent the watery part of the tears from evaporating too quickly, stabilizing the tear film. The rheum also contains shed skin cells and environmental dust trapped throughout the day.
The moisture in the tear film evaporates overnight, leaving behind the dried or sticky residue of mucin, oil, and debris. This accumulation causes the discharge to be crusty in the morning, ranging from clear to a pale cream or slight yellow color. The normal function of this process is to remove irritants and waste products from the front surface of the eye.
Identifying Abnormal Discharge: Indicators and Underlying Causes
While a small amount of clear or whitish crust in the morning is typical, a change in the color, consistency, or volume of discharge suggests an underlying issue. The appearance of the discharge provides clues about the specific cause of irritation or infection. Excessive or unusual discharge that persists throughout the day signals that the eye’s cleansing system is overwhelmed.
Bacterial Infections
A thick, opaque discharge that is yellow, green, or gray often indicates a bacterial infection, most commonly bacterial conjunctivitis. This discharge is frequently pus-like and can cause the eyelids to stick completely shut upon waking. The color comes from white blood cells sent by the immune system to fight the infection.
Viral and Allergic Causes
Clear, watery, or slightly stringy discharge is often associated with viral infections or allergies. Viral conjunctivitis, which is highly contagious, typically produces a clear, excessive, and watery discharge. Allergic conjunctivitis, triggered by irritants like pollen or dander, also results in a watery discharge, sometimes accompanied by a stringy, white mucus component.
Other Conditions
A stringy, white, or foamy discharge can also be a sign of dry eye syndrome or blepharitis (inflammation of the eyelids). Dry eye disrupts the balance of the tear film, leading to a sticky, mucus-heavy residue. Blepharitis, often related to clogged oil glands, causes waxy or crusty debris along the lash line and can sometimes produce foamy discharge. Abnormal discharge can also result from a blocked tear duct, which prevents proper drainage and leads to a constant buildup.
Hygiene Practices and When to Consult a Doctor
The safest way to remove normal or mildly excessive eye discharge is through gentle cleaning with a warm compress. Soak a clean washcloth in warm water, wring it out, and apply it to the closed eye for a few minutes to soften any crusty material. Gently wipe the discharge away, moving from the inner corner of the eye outward. Use a fresh, clean part of the cloth or a new cotton ball for each wipe.
Avoid touching the eyes with unwashed hands to prevent spreading infection. If an infection is suspected, wash linens frequently in hot water and avoid sharing them. Contact lens wearers must switch to glasses until symptoms have fully resolved.
You should seek medical advice if the discharge is accompanied by concerning symptoms:
- Severe eye pain.
- Sudden changes in vision or blurred vision.
- Extreme sensitivity to light.
- Swelling around the eye area.
- Discharge that is dark yellow or green and constant throughout the day.
If the discharge does not clear up after a week of home management, consult a doctor to determine the underlying cause and appropriate treatment.