The color of the sclera, or “whites” of the eyes, can vary from person to person. However, in most cases, the sclera has a white or off-white appearance. This is because the sclera is composed of dense connective tissue containing collagen and extracellular matrix that scatters light. A healthy, normal sclera appears white or pale yellow as a result of this light scattering. Certain medical conditions orfactors can cause the sclera to become yellowish or jaundiced in appearance. Understanding the causes of yellowish sclera can help provide insight into a person’s health.
Anatomy of the Eye
The sclera is the outermost layer of the eyeball and consists of dense irregular connective tissue. It helps maintain the shape of the eye and protects the inner structures. Under the sclera is a vascularized layer called the choroid, followed by the retina. The choroid contains blood vessels that provide oxygen and nourishment to the eye. At the front of the eye, the sclera transitions into the cornea, which is transparent and allows light to enter the eye. The white appearance of the sclera is due to the arrangement of collagen fibers in the connective tissue matrix as well as minimal vascularization. This causes light passing through to be reflected and scattered, giving it a white look.
Normal Sclera Color
The normal color of the sclera ranges from white to pale yellow in healthy individuals. The whiteness comes from the light scattering properties of the collagen matrix as mentioned earlier. However, there can be subtle variations in color between different people. Several factors contribute to this:
– Thickness of the sclera – Thinner sclera transmits more vascularized choroid underneath, causing a slightly bluish hue. Thicker sclera appears more white.
– Pigmentation – Higher levels of melanin pigment in the sclera lead to a whiter appearance. Those with less pigment have more choroidal show-through and a subtle yellowish/blueish color.
– Blood vessel redness – More blood flow to the choroid layer can cause the sclera to take on a slightly reddish or pinkish hue. This is often seen transiently with eye strain.
– Natural variations – There are simply inherent differences in collagen density and melanin levels between individuals that account for normal variety in sclera hues.
So while the sclera is classically described as “white”, normal, healthy eyes can range from white to pale yellow without necessarily indicating any medical problems. However, more prominent or localized yellowing may be a sign of underlying issues.
Causes of Yellow Sclera
There are various medical conditions that can cause the sclera to take on a yellow or jaundiced appearance:
– Jaundice – Elevated bilirubin levels in the blood from liver diseases like hepatitis turn the sclera yellow along with the skin in jaundice patients. Bilirubin accumulates in the collagen fibers of the sclera.
– Infection – Yellow eye discharge in bacterial or viral conjunctivitis can stain the sclera yellow. Also seen in epidemic keratoconjunctivitis.
– Pinguecula – Yellowish patches on the white of the eye due to UV light exposure aging the conjunctiva. Common in elderly.
– Pterygium – Fleshy tissue growth on conjunctiva that can look yellowish in the sclera. Caused by UV damage and dry eyes.
– Hyperlipidemia – High cholesterol and triglycerides leading to yellowish cholesterol deposits called xanthelasma.
– Aniridia – Genetic defect causing partial or total absence of the colored iris. This uncovers the yellowish choroid below giving the sclera a yellow tint.
– Neroflbromatosis – Genetic disorder causing yellowish choroidal nodules visible through the sclera.
– Medications – Certain drugs like tamoxifen and chloroquine can bind to melanin in the sclera and cause brownish discoloration.
– Chemical exposure – Industrial chemical fumes may react with melanin in the sclera, turning it yellow-brown. Seen in copper and sulfur dioxide toxicity.
– Aging – With age, the sclera can gradually become more yellow due to fat deposits, thinning, and collagen changes.
When to See a Doctor
While some causes of yellowish sclera like age-related changes may be benign, others can signal more serious illnesses. You should see an optometrist or ophthalmologist if the yellowing:
– Is accompanied by other symptoms like itchiness, discharge, pain, swelling, excessive tearing, vision changes, jaundice of the skin.
– Only affects one eye.
– Has an unequal or irregular distribution rather than being diffusely yellow.
– Is associated with growths, lumps, or colored patches on the white of the eye.
– Appears suddenly rather than gradually developing.
– Occurs in children or young adults with no family history or risk factors.
– Is unexplained – you haven’t started any new medications, don’t have pre-existing conditions, and haven’t suffered eye injuries.
An eye exam can help determine if infections, structural defects, masses, inflammation or other problems are causing the yellowish discoloration. Blood tests may also diagnose conditions like jaundice.
Treatment
Treatment for yellow sclera focuses on the underlying cause. Some options include:
– Antibiotics for infectious conjunctivitis
– Steroids and immunosuppressants for autoimmune conditions
– Antiviral medications for viral infections
– Surgery to remove pterygia or xanthelasma growths
– Lowering cholesterol and triglycerides
– Stopping causative medications
– Phototherapy for neonatal jaundice
– Supplements like lutein and zeaxanthin for age-related yellowing
For benign causes like aging, no specific treatment may be needed beyond routine eye exams. The yellowish discoloration itself is not harmful in those cases. However, any changes in appearance should be monitored by an ophthalmologist.
Prevention
You can take some steps to help prevent yellowing of the sclera:
– Wear sunglasses to block UV rays that can damage the conjunctiva and collar areas.
– Use preservative-free lubricating eye drops if you have dry eye problems.
– Maintain normal lipid levels through diet and exercise.
– Have routine dilated eye exams to check for early signs of pinguecula, pterygium, or growths.
– Avoid irritants and rubbing your eyes which can worsen problems like infections and dry eyes.
– Wear protective goggles when exposed to chemical sprays at work.
– Treat illnesses like hepatitis to prevent bilirubin buildup and jaundice.
– Follow medication instructions carefully and notify your doctor of any eye changes.
Conclusion
The normal sclera is white, but can range naturally in appearance from white to pale yellow depending on pigmentation, vascularity, thickness, and other factors. However, prominent yellowing or jaundice of the sclera is often indicative of underlying illness such as liver problems, cholesterol issues, infections, autoimmune conditions, and ocular diseases. Elderly individuals may gradually develop more yellowing due to aging changes. Seeing an ophthalmologist promptly for evaluation is recommended if the yellowing is new, unilateral, irregular, associated with other symptoms, or without obvious explanation. Treatment depends on the cause but may include medications, supplements, surgery, lifestyle changes, and regular eye exams. Precautions like sunglasses, eye lubrication, controlling lipid levels, and avoiding irritants can help minimize certain risks. Overall, while some scleral yellowing can be normal, significant changes in color warrant medical assessment.
