- The cornea is the transparent, dome-shaped front part of the eye that covers the iris, pupil, and anterior chamber. It plays a crucial role in vision by acting as the eye’s primary refractive surface, bending (refracting) incoming light rays so they can be focused precisely on the retina at the back of the eye.
- The cornea accounts for about two-thirds of the eye’s total optical power, making it essential not only for clarity of vision but also for overall ocular health. Its transparency, avascularity, and smooth curvature allow it to function as a powerful lens while also serving as a protective barrier against environmental damage.
- Structurally, the cornea is composed of five distinct layers, each with specialized functions:
- Epithelium – the outermost layer that serves as a barrier to dust, water, and pathogens; it also absorbs oxygen and nutrients from tears.
- Bowman’s layer – a tough, acellular layer that provides additional structural integrity.
- Stroma – the thickest layer, consisting of regularly arranged collagen fibers and keratocytes, which maintain the cornea’s strength, elasticity, and transparency.
- Descemet’s membrane – a thin but strong basement membrane that supports the endothelial layer.
- Endothelium – the innermost layer, responsible for regulating fluid balance in the cornea and maintaining its clarity by actively pumping out excess water from the stroma.
- The cornea is avascular—it contains no blood vessels—so it relies on diffusion from tears, the aqueous humor, and surrounding capillaries for nourishment. Its rich supply of nerve endings makes it one of the most sensitive tissues in the body, allowing it to respond quickly to injury or foreign particles through blinking and tearing.
- Diseases and injuries affecting the cornea can significantly impair vision. Common conditions include keratitis (inflammation of the cornea), corneal ulcers, dry eye syndrome, keratoconus (progressive thinning and bulging of the cornea), and corneal dystrophies (genetic disorders that affect the cornea’s clarity). Trauma, infections, or systemic deficiencies—such as vitamin A deficiency leading to xerophthalmia or keratomalacia—can also damage the cornea. When the cornea becomes scarred or opaque, light cannot pass through properly, resulting in blurred or lost vision.
- Treatment for corneal conditions varies depending on the cause. It may include antibiotics or antivirals, lubricating eye drops, anti-inflammatory medications, or corrective lenses. In cases of severe damage or disease, corneal transplantation (keratoplasty) may be required, where the damaged corneal tissue is replaced with healthy donor tissue.
