The sclera, the “white” part of the eye, is a protective outer layer covering much of the eyeball. While often seen as perfectly white, its appearance can vary naturally or due to underlying conditions. Understanding these variations helps determine when a deviation from pure white indicates a health concern.
Understanding Scleral Appearance
A healthy sclera appears white, providing a strong, opaque coat for internal eye tissues. It is not always a uniform, pristine white. Tiny, normal blood vessels are often visible, giving a subtle reddish tint in some individuals. With age, the sclera may develop a slight yellowish hue, a common and harmless variation. In infants, the sclera can appear bluish due to its thinner nature, allowing the underlying dark choroid layer to be more visible. These minor deviations are considered normal and do not signal a problem.
Why Eyes Might Appear Yellow
Yellowing of the sclera, known as jaundice, indicates an excess of bilirubin in the bloodstream. Bilirubin is a yellow pigment formed when red blood cells break down; normally, the liver processes and removes it. When the liver malfunctions, bilirubin accumulates, leading to yellowing of the skin and eyes.
Liver diseases like hepatitis cause yellowing by impairing the liver’s ability to filter bilirubin. Cirrhosis, a chronic scarring of the liver, also interferes with bilirubin processing. Blockages in the bile ducts, often from gallstones or tumors, prevent bilirubin excretion, leading to buildup. Certain medications can also induce yellowing by affecting liver function or causing hemolysis, the destruction of red blood cells.
Why Eyes Might Appear Red
Redness in the eyes can stem from various causes, from mild irritation to more serious conditions. Common reasons include fatigue or environmental irritants like dust or smoke. Allergies can trigger allergic conjunctivitis, where the immune system releases histamine, causing blood vessels to enlarge, leading to redness, watering, and itching.
A subconjunctival hemorrhage appears as a bright red patch on the sclera due to a broken tiny blood vessel, often caused by straining, coughing, or sneezing. Though dramatic, these are harmless and resolve within days to weeks. More concerning causes include infections like viral or bacterial conjunctivitis (pink eye), which inflames the conjunctiva and can produce discharge. Dry eye syndrome, where insufficient tears cause irritation, and acute angle-closure glaucoma, a sudden increase in eye pressure, can also manifest as red eyes, with glaucoma potentially causing severe pain and rapid vision changes.
Other Scleral Color Changes
Beyond yellow and red, the sclera can exhibit other color variations. A blue or grayish tint may occur if the sclera is thinner than usual, allowing the underlying dark blood vessels of the choroid to show through. This can be normal in infants or associated with genetic conditions affecting connective tissue, such as osteogenesis imperfecta (brittle bone disease), where collagen is not formed correctly, leading to thinner sclerae.
Brown spots on the sclera can be harmless, resembling freckles or nevi (moles) due to high melanin levels. However, some brown spots, like primary acquired melanosis (PAM), can be precancerous and require monitoring. Long-term use of certain medications, such as the antibiotic minocycline, can also lead to a blue-gray discoloration.
When to Consult a Doctor
Any sudden or significant change in sclera color warrants medical attention. If you notice persistent yellowing, especially with symptoms like abdominal pain, fatigue, or fever, seek prompt evaluation. Similarly, persistent redness, particularly if accompanied by eye pain, vision changes, discharge, or light sensitivity, should prompt a visit to an eye care professional. Early diagnosis and treatment are important for managing underlying health conditions indicated by these changes.