Cornea: Structure, Function, Disorders, Refractive Surgeries, Transplantation Quiz

Cornea: Structure, Function, Disorders, Refractive Surgeries, Transplantation

The cornea is a transparent structure towards the front of the eye, responsible for a significant portion of the eye's refractive power. It is composed mostly of water, with 80% hydration and only a small percentage of living cells.

Structure

The cornea is a dome-shaped structure that is about 1 cm in diameter and 0.5 mm thick in the center, and 1.2 mm thick near the periphery. It is composed of five layers:

1. Outer layer (epithelium): This layer is about 5 microns thick and has 5 to 6 layers of epithelial cells.
2. Anterior stroma (lamina propria): This layer is composed of irregularly arranged collagen fibers and contains 90% of the corneal thickness.
3. Posterior stroma: This layer contains regularly arranged collagen fibers and is responsible for the cornea's transparency.
4. Descemet's membrane: This layer is a fibrous membrane that separates the stroma from the corneal endothelium.
5. Corneal endothelium: This layer is a single layer of cells that pump out excess fluid from the cornea to maintain its transparency.

Function

The cornea serves several functions:

1. Refractive power: It is the primary refractive structure of the eye, focusing light towards the retina to create a sharp image.
2. Protection: It acts as a barrier to protect the eye from dust, dirt, and other foreign particles.
3. Light filtration: It filters out most of the ultraviolet and blue light, protecting the retina from damage.
4. Healing: It has a high capacity for self-repair and regeneration, making it resilient to injury.

Disorders

Several disorders can affect the cornea, including:

1. Infections: Bacterial, viral, and fungal infections can cause corneal ulcers or keratitis.
2. Trauma: Injuries from accidents or sports can cause corneal abrasions or lacerations.
3. Deterioration: Age-related deterioration can cause opacification, leading to vision loss.
4. Dry eye: Tear deficiency can lead to corneal drying and inflammation.
5. Allergies: Eye allergies can cause redness, itching, and watering of the eyes.

Refractive Surgeries

Refractive surgeries are procedures that change the shape of the cornea to improve vision:

1. LASIK (laser-assisted in situ keratomileusis): This procedure uses a laser to reshape the cornea, reducing the need for glasses or contact lenses.
2. PRK (photorefractive keratectomy): This procedure also uses a laser to reshape the cornea, but without creating a flap like LASIK.
3. RLE (refractive lens exchange): This procedure involves replacing the eye's natural lens with a lens implant to correct refractive errors.

Transplantation

Corneal transplantation, also known as keratoplasty, involves replacing a damaged or diseased cornea with a healthy one from a donor. This procedure can be used to treat conditions such as keratoconus, corneal ulcers, and corneal dystrophies.