The Sclera: The White of the Eye & Related Eye Conditions

In the simplest terms, the sclera represents the “white” of the eye or the white portion of the eye that surrounds the colored portion, or iris. 

Conditions that affect the sclera include ectasia, episcleritis, sclera coloboma, scleritis, and senile scleral plaques. Additional conditions can potentially trigger color changes in the sclera, such as a burst blood vessel causing pinkness or redness, or jaundice causing the sclera to take on a yellowish hue.

What Does the Sclera Do?

The sclera is designed to support the eyeball, protect it from injury and maintain its shape. Clear mucus membranes cover the sclera, which are called conjunctiva. They lubricate the eye, protecting it from dryness and disease.

The sclera provides an opaque coat for the intraocular tissues, giving the eyeball support when it moves or is affected by internal pressure. The connective tissue of the sclera then allows for better focusing.

Layers of the Sclera

The white of the eye is made up of four layers, as follows:

Episclera

This layer is a thin and clear tissue that rests on top of the white of the eyeball.

Stroma

This layer is made of collagen fibers and fibroblasts that mix with the episclera.

Lamina Fusca

This layer is transitional, resting between the sclera and the choroid. 

The choroid is a thick layer of tissue that is part of the mid layer of the eye’s wall. It sits between the sclera or white outer layer of the eye and the retina. 

The retina represents the inner layer of nerve tissue that is located in the back of the eye. This is the part of the eye that sends electrical signals to the optic nerve, so the eye can create images.

Endothelium

This layer is the innermost layer of the sclera. It is also called the basal layer of the sclera.

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Which Eye Conditions Affect the Sclera?

While any disease of the sclera is rare, its presentation can quickly destroy vision if the problem isn’t immediately addressed.  

Below are some of the conditions that affect the sclera sometimes. Most of these conditions have an underlying cause or emerge because of another health condition.

Ectasia

If you’ve been hit in the eye or the eyeball becomes inflamed, it may lead to a thinning or bulging of the sclera called ectasia.

Treatment

While this condition often heals on its own, you may have to be fitted with special contact lenses and wear them part-time for several days.

Episcleritis

This condition involves swelling and inflammation of the outer layer of the sclera. It is often related to an inflammatory ailment, such as rheumatoid arthritis. The eyes become tender, swollen, and red. Patients may also complain about sensitivity to light, or photophobia.

Treatment

Episcleritis normally resolves on its own, but it may return. Eye doctors treat the condition with an oral nonsteroidal anti-inflammatory drug,  which is usually taken three times per day. It may also be treated with alternative medicines such as indomethacin or flurbiprofen, given two and three times per day, respectively.

Sclera Coloboma

This congenital condition occurs when a piece of tissue is missing at birth. In turn, the patient’s eyeball develops a notch or bulge. Patients experience vision loss and sensitivity to light.

People with small eyes (microphthalmia) or who have conditions such as glaucoma or cataracts often have coloboma. 

Treatment

Depending on the severity of the condition, the eye doctor will help the patient make the most of the vision they already have. Therefore, intervention may include prescription lenses in the form of eyeglasses and contacts, vision aids, or surgery to improve the patient’s appearance.

Scleritis

While scleritis, an infection of the sclera, is similar to episcleritis, it is usually more painful and severe. The pain, which is described as piercing, typically worsens when the patient moves their eyes. This can lead to permanent eye damage and vision loss. It may emerge from an underlying inflammatory condition, injury, or fungus.

The infection commonly affects people from 47 to 60 years old, and it is more prevalent in women. Eyes become swollen, red, and sensitive to light.

Treatment

The eye doctor may treat the condition with corticosteroids or non-steroidal anti-inflammatory drugs (NSAIDs). 

Senile Scleral Plaques

As people get older, calcium deposits may collect on the whites of the eyes. The plaques appear as gray spots at the 3 o’clock and 9 o’clock parts of the sclera. In very rare cases, they may erode the conjunctival surface and cause an infection or irritation.

Scleral plaque buildup most often happens in people who are at least 70 years old.

Treatment

Scleral plaques are usually not treated because they do not present symptoms. However, senile scleromalacia with a scleral defect that can lead to perforation may be treated surgically. Doctors may apply a scleral graft to correct the defect. 

In this case, plaque calcification may lead to complications during surgery when correcting future eye problems or conditions. The sclera may be resistant to an incision. 

Conditions That Colorize the Sclera

Some conditions that affect the sclera change the color of the sclera or appear as colored dots.

Blue Sclera

If the whites of the eyes are thinner, the blood vessels may give them a blue or gray cast. This may occur when a person has a genetic bone disease or a disorder that affects the body’s connective tissue, such as Marfan syndrome. An iron deficiency or anemia can also give the sclera a blue coloring.

Some medications, such as minocycline (an antibiotic), can tint the sclera gray or blue.

Treatment

Treatment often entails addressing the underlying cause of the condition. Sometimes, switching out medications may help.

Icteric Sclera

An icteric sclera, or a yellow sclera, may develop when a person has jaundice. Jaundice is a liver disease that happens when the liver is not filtering the blood properly.

Treatment

Treatment involves addressing the underlying cause of the eye condition or treating the liver disease. In adults, treatment for jaundice may include removal of the gallbladder or a change in medication.

Injury to the Eyeball

If you injure your eyeball, you might notice a vivid red spot on the sclera. This discovery indicates a broken blood vessel. 

Treatment

When a sclera has a red spot or multiple red spots, the condition is usually harmless and will resolve itself after a week or two.

Irritated Eyes

The sclera may become irritated, indicated by red or bloodshot eyes, because of eye strain, allergies, or smoke.

Treatment

Resting the eye as well as reducing your exposure allergens and smoke can reduce irritation. The redness will generally clear on its own.

Melanosis

Some sclerae may show hyperpigmentation. This congenital condition often appears in Asian individuals. The spots, which are harmless, result from high levels of melanin. 

Treatment

Also called scleral melanocytosis, this condition is not treated when it affects people of Asian descent. In Caucasian individuals, the condition may increase the risk of uveal melanoma. Therefore, these patients require lifetime monitoring.

Primary acquired melanosis (PAM) occurs when the small spots (usually brown) on the sclera change over time. This type of condition should be reported immediately, as it could indicate a precancerous condition.

Pinguecula

In some cases, a small and slightly yellow growth, called a pinguecula, may project from the sclera. The raised growth develops on the conjunctiva next to the border where the iris and sclera meet. You can have more than one growth in an eye, and it may appear bilaterally.

This damage comes from overexposure to dust, wind, or UV rays. When this happens, the growth may become inflamed and become pink or red. To prevent the growth, you should always protect the eyes with eyewear that shields from wind and UV rays.

Treatment

If the pinguecula becomes inflamed, the eye doctor may advise that you apply artificial tears, ointments, or gels to lubricate the eye. This frequently will reduce irritation and pain. If the condition becomes more severe, topical steroid drops may be used to reduce the inflammation.

Pterygium

If you don’t treat a pinguecula, it can get bigger and form into a pterygium. If this happens, the growth can expand into the cornea and distort or block your eyesight. This growth is also called surfer’s eye.

Treatment

Only surgery can treat this type of lesion. An eye doctor may use one of several techniques to safely remove the growth.

Prompt Treatment Needed for Sclera Conditions

While conditions affecting the sclera are not all that common, they should be addressed as soon as possible. Any hyperpigmentation, colored spots, or growths require immediate medical attention. 

If you are unsure if something is a legitimate issue, it’s always best to have it examined by an eye doctor.

References

1. What Is Scleritis? (September 2022). American Academy of Ophthalmology.

2. Scleral Structure, Organisation and Disease. A Review. (March 2004). Experimental Eye Research.

3. Episcleritis. (September 2022). EyeWiki, American Academy of Ophthalmology.

4. At a Glance: Coloboma. (December 2021). National Eye Institute.

5. At a Glance: Anophthalmia and Microphthalmia. (October 2021). National Eye Institute.

6. Scleritis. (January 2022). StatPearls.

7. Senile Scleral Plaque. (October 2022). EyeWiki, American Academy of Ophthalmology.

8. Unilateral Bluish Sclera. (November–December 2018). Indian Journal of Endocrinology and Metabolism.

9. Jaundice in Adults. (February 2017). American Family Physician.

10. Scleral Melanocytosis. (2009). Encyclopedia of Molecular Mechanisms of Disease.

11. Pinguecula. American Optometric Association.

12. What Is a Pinguecula and a Pterygium (Surfer’s Eye)? (September 2022). American Academy of Ophthalmology.

13. Management of Pterygium. (February 2023). American Academy of Ophthalmology.

14. Scleral Structure and Biomechanics. (January 2021). Progress in Retinal and Eye Research.