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What is Sclera?

The Sclera is known to be the white part of the eye surrounding the corona. It covers almost 80% of the area of the eye that the sclera covers, starting from the cornea and extending to the optic nerve. The optic nerve is extended to the back portion of the eye. We can only see a very little portion of the sclera as we can also see the eyeball. The sclera is actually what is the white part of the eye called. Now that we know what is the sclera, let us learn its functions and related issues in detail.

Sclera of Eye

The sclera of the eye is one type of connecting tissue continuing with the stroma layer of the corona. Limbus is known to be the connection part between the clear cornea and the white sclera. The thickness of the sclera ranges from 0.3 mm up to 1 mm. It is made up of small fibres or fibrils of collagen that are generally interlacing and irregular bundles. The flexibility and strength of the eyeball depend on these connective tissues as these form an interweaving arrangement. The sclera has a limited supply of blood and so is usually metabolically inactive. Though sclera has no blood vessels or is known to be avascular, many blood vessels pass through it.

Episclera is a thin layer of connective tissue present in the top of the sclera, the white part of the eye. It’s that transparent conjunctiva that covers the part of the episclera and sclera. It also generates some blood vessels, which are the primary reason for the nourishment of the sclera. Underlying chloride is another reason for the nourishment of sclera. Chloride is nothing but one vascular layer from the eyeball that’s placed between the retina and sclera.

Function of Sclera

  • It maintains the proper function of the eye or eyeball. Intraocular pressure (IOP) also helps in the same sclera function.

  • It protects the eye from any serious damage that might happen from rupture or laceration. 

  • It also protects the eyeball from any external trauma. 

  • Extraocular muscles are responsible for eye movement. The sclera provides one type of sturdy attachment to these muscles. This is another important sclera function. It helps to locate the sight, particularly where one individual is looking. It makes it easier when it comes to non-verbal communication.

  • Low-velocity injury can’t go through the sclera. 

  • It is rarely injured by heat hence protecting the eye indirectly. 

  • The sclera is also resistant to toxic chemicals, thereby protecting the eye. The reflexive mechanism that is tears easily wash away the chemicals. Sclera eye function protects the eye in many ways.

Different Problems Related to the Sclera

Scleral Icterus or yellow eyes is one eye condition where the sclera becomes yellowish. This happened when someone got liver issues or hepatitis. Though there is some controversy regarding the fact where researchers state that jaundice or yellowing of the eye actually occurs in the part of the conjunctiva. However, many doctors call such issues scleral icterus. Bilirubin or blood serum increment is known to be the reason for jaundice or yellow eye. If you have any such issues immediately, the doctor's suggestion would be to do a blood test that will identify the issue if it's related to a liver problem or not.

Blue Sclera is thinning of sclera from any kind of disease that finally shows choroidal issues that appear through it. Hereditary and congenital diseases are the main reason for such conditions. Brittle bone disease (osteogenesis imperfect) and connective tissue disorder or Marfan's syndrome are some of the reasons. Anaemia or iron deficiency can also cause blue sclera.

Episcleritis or episclera inflammation is a common disease associated with the sclera. This has two types. One is nodular episcleritis, and another is simple episcleritis. The former one is the redness of the overlying tissue portion of the sclera. Later one happens when dilated blood vessels (episcleral) occur in the presence of a nodule. But the fact is most of the reasons for episcleritis are yet unknown. But a few people who get this condition generally go through systematic disorders like rheumatoid arthritis, rosacea, ulcerative colitis, gout, etc.

Scleritis is one eye condition where both episclera and underlying sclera inflammation starts. This is a red-eye condition with a painful situation. This also is the reason for systemic diseases. This can cause vision loss conditions even permanent damage to the eyes.

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FAQs on Sclera

1. What is the colour of the normal sclera?

White parts of the eye sclera are normally white in colour. This covers almost 80% of the eye area. This has connecting tissues throughout. This provides the eyeball with protection from external threats. A healthy Sclera is always known to be white in colour. However, many a time, people notice sclera colour to be discoloured or yellowish. This may happen due to many reasons. Different systematic disorders or diseases could be the reasons. Sometimes, gout, arthritis, anaemia etc., are the main reasons for discolouration. But the good news is these diseases are curable, and once cured, the colour of the sclera becomes normal white again. 

2. What do you understand by scleral buckle?

This is not a sclera related issue. It is just the name of a surgical procedure that is used to repair a detached retina. In this process, a silicon band, semi-hard plastic or rubber is usually placed from the mid-range of the sclera. This buckles the sclera inward, resulting in the loosening up of rental tissue and eventually giving the inner wall of the eye resting. Then the eye surgeon usually uses extreme cold or cryopexy or laser photocoagulation to repair or seal retinal tissue against the eyeball wall. This technique has been used to repair the detached retina. 

3. What is the scleral lens, and how does it work?

The scleral lens is known to be very useful for different ocular conditions. A scleral lens is an oxygen permeable large-diameter lens. This is in no way related to the cornea. This helps in the process of vision restoration and can be done in a very comfortable manner. This protects the coronal from the external environment. This also provides oxygen to the cornea allowing gradually healing of the eye. The technicality of this lens creates an optical surface over the compromised cornea and replaces those distorted surfaces. In every case, it has been noticed that the scleral lens improved comfort and vision of the eye drastically.