Conjunctiva Vs Sclera Explained with Key Differences

The main distinction between the sclera and conjunctiva is that the conjunctiva is the thin translucent layer that surrounds the whole eye, with the exception of the cornea, and the sclera is the thick white layer that forms the white portion of the eye. More than 80% of the eye, including the cornea, is covered with white sclera. The conjunctiva is the thin, translucent covering that covers the sclera and inner surface of the eyelids.

The sclera has a small blood supply, whereas the conjunctiva has a high level of vascularization. The togetherness of the conjunctiva and sclera is important for healthy eyes and when it is compromised the ocular system is affected. One such condition is Pinguecula, which is a nonmalignant, lesion in the interpalpebral bulbar conjunctiva. The yellowish lesion is due to the disintegration of elastic tissue and subepithelial collagen.

Conjunctiva of Eye

The conjunctiva of the eye seems to be the transparent, thin membrane that lines the interiors of the eyelids and a portion of the front of the eye. The conjunctiva is the membrane that covers the sclera, the tough white fibre layer that covers the eye, up to the edge of the cornea. It lines the eyelid (the clear layer in front of the iris and pupil). The conjunctiva contributes to the maintenance of the tear film and serves as a barrier against microscopic foreign objects and bacteria that can cause infections.

Conjunctiva Parts and Anatomy

The palpebral or tarsal, bulbar or ocular, and conjunctival fornices are the three parts of the conjunctiva. Marginal, tarsal, and orbital regions make up the remainder of the palpebral conjunctiva. Scleral and limbal portions make up the bulbar conjunctiva. The superior, inferior, lateral, and medial regions of the conjunctival fornices are the final divisions.

The conjunctiva palpebral lines the eyelids. On the eyeball, the anterior sclera is covered by the bulbar conjunctiva. It adheres to the underlying sclera thanks to Tenon’s capsule. The conjunctiva of this eye is 33 microns thick on average. Last but not least, the intersection of the palpebral and bulbar conjunctiva is formed by the conjunctival fornices. Contrary to its bulbar counterpart, this protective covering is loose and flexible, allowing the globe and eyelids to move. Conjunctiva layers from outside to inside are epithelium, adenoid layer, and Fibrous layer.

Functions of Conjunctiva

• Conjunctiva functions as eye lubricant through the production of mucus and tears, and thus protects the eye.

• It guards the immune system and stops microbes from getting inside the eye. It provides a covering for the sclera and lines the inside of the eyelids.

• It has numerous lymphatic vessels and is highly vascularized.

Sclera

Strong tissue that surrounds the eyeball is known as the sclera, or white of the eye. It shields your eyeball from harm and aids in maintaining its shape. The outermost, hard layer of the eyeball is called the sclera. It is white. The eyeball's sclera gives it structural support and guards against rupture and piercing. The entire sclera can change colour or develop coloured spots for a variety of reasons. Many scleral issues go away on their own in a few weeks, but not all of them do.

Sclera Parts and Anatomy

From the exterior to the interior, the sclera is made up of four layers: The episclera is the transparent, delicate tissue that covers the whites of your eyes. Fibroblast- and collagen-fiber-rich stroma fusing with the episclera. Between the sclera and the choroid and ciliary body, the outer layer is a layer known as the lamina fusca.

Functions of Sclera

The sclera serves as the eyeball’s retaining wall. It safeguards your eyeball from harm and aids in maintaining its shape. Conjunctiva, which is transparent mucous membranes that lubricate (moisturise) your eye, cover the sclera. Your eyeball can be moved side to side and up and down with the assistance of sclera-attached muscles.

Difference Between Sclera and Conjunctiva

The conjunctiva and sclera are two crucial components of the eye. Both are layers of the eye’s defence system. The sclera, or white component of the eye, covers the cornea and more than 80% of the rest of the eye. The inside lining of the eyelids and the sclera are covered by a thin, translucent membrane called the conjunctiva. The sclera has a small blood supply, but the conjunctiva has a high level of vascularization. Sclera and conjunctiva differences are compared side by side in the infographic below.

Interesting Facts

• The cornea lacks blood vessels, in contrast to other bodily tissues.

• The conjunctiva often recovers quickly from minor wounds on its own.

• Jaundice is indicated by the sclera becoming from white to pale yellow in colour.

• Special cells in the conjunctiva collaborate with the tear film to avoid dry eye syndrome.

Important Questions

1. What is the function of the iris and pupil?

Ans: In case of insufficient light iris allow more light to enter the eye by enlarging the pupil. When the light is bright it causes shrinkage of the pupil allowing less light to enter the eye.

2. What is aqueous humour and its function?

Ans: Aqueous humor is the fluid of the eye that allows the maintenance of the eye in pressurised state. It also provides nutrition to the eye and removes waste from the cornea and lens.

Key Features

• The exterior structures of the eye are made up of two connective tissues called cornea and sclera.

• Sclera discolouration is a relatively frequent occurrence. Because of the lipids that are deposited, the sclera’s colour can change with age, becoming darker, redder, and yellower.

• The main distinction between the sclera and conjunctiva is that the former is the thick white layer that makes up the white portion of the eye, whilst the latter is the thin translucent layer that covers the entire eye, with the exception of the cornea.