The experience of waking up to find a gooey or crusty substance collected in the corner of the eye is common. This material, often called “sleep” or “eye gunk,” is medically known as rheum or gound. Rheum is essentially a mix of mucus, oil, and discarded cells the eye uses to clean itself throughout the day. While a small amount of this discharge is a routine sign of healthy eye function, changes in its color, consistency, or volume can signal an underlying health issue.
The Normal Stuff: Understanding Rheum
The eye constantly produces a tear film composed of three layers: watery, oily (meibum), and mucus (mucin). Mucin helps spread the tear film evenly across the eye’s surface, while meibum prevents the watery layer from evaporating too quickly. As the eye cleans itself, it flushes away debris, dust, and old cells, which become trapped in this tear film.
During the day, the continuous action of blinking washes this material through the tear ducts, preventing it from building up. However, when a person sleeps, the eyes are closed and the blinking mechanism stops, allowing this debris to collect. As the liquid portion of the tears evaporates overnight, the remaining combination of mucus, oil, and cellular waste dries out, forming the crusty or gooey substance known as rheum.
Normal rheum is typically clear, whitish, or a light cream color, and it is easily wiped away. This minor accumulation is a function of a healthy, working tear system. The substance is protective, as it removes waste products from the front surface of the eye. If the discharge is mild, clear, and does not accompany symptoms like pain or redness, it is considered a normal byproduct of sleep.
When Discharge Signals Infection
An eye infection often causes a marked change in the appearance and volume of eye discharge. The most common infectious cause is conjunctivitis, frequently referred to as pink eye, which inflames the thin, transparent membrane lining the eyelid and covering the white part of the eye. Differentiating between the types of pink eye is often possible by examining the discharge consistency and color.
Bacterial conjunctivitis typically produces a thick, opaque discharge that is yellow or greenish in color. This type of discharge is frequently abundant and sticky enough to cause the eyelids to mat or seal shut, especially after waking from sleep. Common bacteria responsible include Staphylococcus aureus and Streptococcus pneumoniae. This heavy, pus-like material indicates the presence of white blood cells fighting the infection.
Viral conjunctivitis, often caused by adenoviruses, usually results in clear, watery discharge, though it may include a white or light yellow mucus component. This type is highly contagious and often causes excessive tearing and severe redness. Viral infections are sometimes accompanied by symptoms of an upper respiratory infection like a cold.
Non-Infectious Causes of Discharge
Not all instances of excessive or abnormal eye discharge point toward an infection; many are related to environmental factors or chronic conditions. Allergic conjunctivitis, triggered by allergens like pollen or dust, produces discharge that is typically clear, watery, and sometimes stringy. This discharge is also accompanied by intense itching and often affects both eyes simultaneously.
Dry eye syndrome is another common cause, manifesting when the tears are either insufficient in quantity or poor in quality. When the tear film is imbalanced, the mucus and oil components can combine to form a sticky, stringy, or even foamy discharge. This foamy or stringy mucus is the eye’s compensatory response to the lack of adequate moisture. The discharge from dry eye can often be crusty upon waking, but it is more noticeable and persistent throughout the day.
Environmental irritants and poor hygiene practices also provoke the eye to produce abnormal discharge. Exposure to smoke, dust, or chemicals can cause the eye to secrete a watery discharge to flush out the foreign body. Similarly, wearing contact lenses for extended periods or failing to clean them properly can irritate the eye, leading to increased mucus production. In these non-infectious scenarios, the discharge is generally less thick and less opaque than that caused by a bacterial infection.
When to Seek Professional Help
While most mild, clear, or white morning discharge is harmless, certain symptoms warrant a consultation with an eye care professional. A sudden or sustained change in vision clarity, severe eye pain, or intense sensitivity to light should be addressed immediately.
You should seek prompt medical attention if the discharge is thick, yellow, or green and causes your eyelids to be sealed shut. This presentation is highly suggestive of a bacterial infection that may require prescription antibiotic treatment. Any discharge that is persistent, worsens over a period of 24 to 48 hours, or is accompanied by a fever or chills also requires professional evaluation.
If you wear contact lenses and develop any eye irritation or discharge, remove the lenses and wear glasses until a professional can determine the cause. For mild cases of irritation, a warm compress may help remove crusted discharge. If home care steps do not resolve the symptoms within a couple of days, or if you suspect an infection, consulting a doctor is the appropriate next step.