Sclera

Overview

What is the sclera?

The sclera, or white of the eye, is a protective covering that wraps over most of the eyeball. It extends from the cornea in the front to the optic nerve in the back.

This strong layer of tissue, which is no more than a millimeter thick, gives your eyeball its white color. It also protects and supports your eye. The plural for sclera is sclerae.

Function

What does the sclera do?

The sclera functions as the supporting wall of the eyeball. It helps maintain your eyeball’s shape, and protects it from injury.

The sclera is covered by conjunctiva, which are clear mucus membranes that lubricate (moisturize) your eye. Muscles attached to the sclera help move your eyeball up and down and side to side.

Anatomy

What is the anatomy of the sclera?

The sclera is made of tough collagen fibers, which crisscross in random directions. That random pattern gives your eyeball its white color and gives the sclera strength. This contrasts with the collagen fibers in your cornea, which are very organized and allow the cornea to be clear.

The sclera has four layers, from the outside to the inside:

  • Episclera, clear, thin tissue resting on top of the whites of your eyeballs.
  • Stroma, made up of fibroblasts and collagen fibers, blending into the episclera.
  • Lamina fusca, a transitional layer between the sclera and the choroid and ciliary body outer layers.
  • Endothelium, the basal, or innermost layer of the sclera.

Conditions and Disorders

Why isn't the sclera of my eye white?

Several things can cause the entire sclera to change color or spots of color to appear:

  • Blue sclera: If the sclera is thinner than normal, blood vessels may show through, giving your eyeballs a blue or gray hue. This may occur in people with certain health conditions. Examples include osteogenesis imperfecta (a genetic bone disease) and Marfan syndrome (a disorder in connective tissue throughout the body). Other examples include iron deficiency and anemia.
  • Icteric sclera and jaundice: If the entire sclerae turn yellow, that could mean you have jaundice. Jaundice indicates liver disease, which means the liver isn’t filtering blood properly.
  • Injury: If your eyeball is injured, it may have a bright red spot. This indicates a broken blood vessel that has leaked some blood. These red spots are usually harmless and go away in a few days or weeks.
  • Irritation: If your eyes are “bloodshot,” you can see redness throughout the sclerae. Eyes may be irritated due to smoke, allergies, exhaustion or infection.
  • Medication: Some medications can tint the sclerae blue or gray (for example, an antibiotic called minocycline).
  • Melanosis: Your sclera may contain a flat, brown spot, almost like a freckle. This is more common in Black people. The spots are caused by high levels of pigment called melanin, and they’re harmless.
  • Pinguecula: A small patch of yellow may bulge out from your sclera after damage from the sun, wind or dust. The patch may become inflamed and turn pink or red.
  • Pterygium: If a pinguecula goes untreated, it can get larger, expand into the cornea and block vision.
  • Primary acquired melanosis (PAM): If you have a flat brown spot on the eye that changes over time, this may indicate PAM. This condition can become cancerous, so report any new or changing spots on the sclera.

What other conditions and disorders affect the sclera?

Other problems with the sclera include:

  • Ectasia: When your eyeball experiences trauma (injury) or inflammation, the sclera may thin or bulge. This may heal on its own, or you may need special contact lenses.
  • Episcleritis: This is inflammation (swelling) of the episclera. Your eyes may be swollen, tender and red. The condition may be associated with an inflammatory condition, such as rheumatoid arthritis. Episcleritis usually goes away on its own in a few weeks, but it can come back.
  • Scleral coloboma: Sometimes, a piece of tissue is missing in the sclera from birth. It can cause a notch or a bulge in your eyeball. Treatment varies depending on how problematic the condition is. It usually involves helping people protect their eyes and making the most of the vision they have.
  • Scleritis: This condition is similar to episcleritis but is more serious and often more painful. Scleritis often involves piercing pain in your eye that gets worse with eye movement. It can cause permanent damage and vision loss. Treatment options include nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids. It may be caused by an underlying inflammatory disease, fungus or injury.
  • Senile scleral plaques: With age, the sclera can develop calcium deposits. These plaques may appear as gray spots at the 3 and 9 o’clock portions of your sclera. Only rarely can they erode through the conjunctival surface and cause irritation or infection.

How long does it take for the sclera to heal?

Minor injury or inflammation of the sclera often heals in a few days or weeks. But if you have any other symptoms or the problem doesn’t go away, talk to your healthcare provider or ophthalmologist. An ophthalmologist specializes in disorders and diseases of the eyes.

Care

How can I protect my sclerae?

You can help protect your sclerae from injury with several simple strategies:

  • Wear safety goggles when playing sports or doing home repairs.
  • Wear sunglasses to protect your eyes from sun damage, wind and debris.
  • Wash your hands before touching your eyes to prevent infection.

Frequently Asked Questions

When should I call a healthcare professional?

Talk to your healthcare provider if you notice anything different in your sclera, such as:

  • Blurry vision or loss of vision.
  • Bulging.
  • Change in color of the whites of your eyes.
  • Change in an existing spot on the white of your eye (for example, it changes color or gets larger).
  • Discharge (fluid or puss leaking out of your eye).
  • Pain or tenderness.
  • Sensitivity to light.
  • Swelling of your eyeball.

A note from Cleveland Clinic

The sclera is a protective covering that wraps over most of your eyeball. It supports your eyeball and forms the white of your eye. If you experience color changes in the whites of your eyes, especially with pain or vision changes, call your healthcare provider immediately.

Last reviewed by a Cleveland Clinic medical professional on 11/12/2021.

References

  • American Academy of Ophthalmology. Why Are the Whites of My Eyes Discolored? (https://www.aao.org/eye-health/tips-prevention/discolored-sclera-whites-of-my-eyes-turn-yellow) Accessed 11/12/2021.
  • American Academy of Ophthalmology. What Is Scleritis? (https://www.aao.org/eye-health/diseases/what-is-scleritis) Accessed 11/12/2021.
  • National Eye Institute. Keep Your Eyes Healthy. (https://www.nei.nih.gov/learn-about-eye-health/healthy-vision/keep-your-eyes-healthy) Accessed 11/12/2021.
  • Pradeep T, Mehra D. Histology, Eye. (https://www.statpearls.com/ArticleLibrary/viewarticle/32704) [Updated 10 May 2021]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. Accessed 11/12/2021.

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