Conjunctiva vs. Cornea — What's the Difference?

The conjunctiva is a thin, flexible membrane that lines the inside of the eyelids and covers the sclera (white part of the eye), playing a crucial role in lubricating the eye by producing mucus and tears. In contrast, the cornea is a clear, dome-shaped surface that covers the front of the eye, including the iris and pupil, and acts as the eye's primary focusing element, bending incoming light to help focus it onto the retina.

While the conjunctiva serves to protect the eye from microbial and mechanical injuries by secreting mucus and tears, thereby keeping the eye moist, the cornea provides a barrier against dirt, germs, and other particles that might cause injury. The cornea also significantly contributes to the eye's total optical power, and its transparency is critical for vision.

The conjunctiva can become inflamed due to infections, allergies, or irritants — a condition known as conjunctivitis, commonly referred to as pink eye. This contrasts with corneal conditions like keratitis (inflammation of the cornea) or corneal ulcers, which often result from infections or wearing contact lenses improperly and can significantly affect vision due to the cornea’s role in light focus.

In terms of anatomical location and structure, the conjunctiva is more flexible and less structured than the cornea, which needs to maintain a precise curvature and thickness to focus light effectively. The cornea is also one of the most sensitive tissues of the body, densely packed with nerve fibers, more so than the conjunctiva.

From a medical treatment perspective, issues with the conjunctiva are often treated with eye drops or simple hygiene measures. In contrast, corneal issues might require more invasive treatments such as corrective lenses, surgery, or in severe cases, corneal transplants, reflecting the critical role of the cornea in vision compared to the primarily protective function of the conjunctiva.