The cornea is the transparent, dome-shaped outer layer of the eye that covers the iris, pupil, and anterior chamber. It plays a crucial role in focusing light onto the retina, enabling vision. Here's a breakdown of its anatomy:
1. **Epithelium**: The outermost layer of the cornea is the epithelium. It acts as a barrier to protect the eye from foreign particles, bacteria, and viruses. The epithelium also helps in maintaining the smoothness of the corneal surface, which is essential for clear vision.
2. **Bowman's Layer**: Beneath the epithelium lies Bowman's layer, a thin, tough layer composed mainly of collagen fibers. It provides structural support to the cornea.
3. **Stroma**: The stroma is the thickest layer of the cornea, making up about 90% of its thickness. It consists of collagen fibers arranged in a precise pattern, which gives the cornea its strength, elasticity, and transparency. The regular arrangement of collagen fibers is crucial for maintaining the cornea's clarity.
4. **Descemet's Membrane**: Descemet's membrane is a thin, acellular layer located between the stroma and the endothelium. It serves as a protective barrier against pathogens and helps maintain the shape of the cornea.
5. **Endothelium**: The innermost layer of the cornea is the endothelium, which is a single layer of cells responsible for regulating fluid and nutrient exchange between the cornea and the aqueous humor (the fluid in the anterior chamber of the eye). The endothelium plays a vital role in maintaining the cornea's transparency by pumping excess fluid out of the stroma.
The cornea lacks blood vessels, relying on the tear film and aqueous humor for oxygen and nutrient supply. Its transparency is essential for clear vision, and any damage or irregularity in its structure can lead to visual impairment. Conditions such as corneal dystrophies, infections, and injuries can affect the cornea's anatomy and function, leading to vision problems.