The cornea is the avascular and transparent layer that covers the pupil and the iris. It is the layer that continues with the sclera and reaches the optic nerve in the posterior part.
The anterior part is in contact with the tear film and the anterior part is in contact with the aqueous humor.
The cornea has the role of a lens that refracts the light that enters directly from the outside to the internal structures of the eye thanks to its anatomical structure:
- Epithelium: is in contact with the tear film.If there is any disease or foreign body that affects this layer, yes it can regenerate.
- Bowman’s membrane: these are collagen fibers. This layer, however, cannot regenerate.
- Stroma: collagen fibers.
- Dua layer
- Descemet membrane: composed of collagen fibers.
- Endothelium: it is in direct contact with the aqueous humor. It is permeable and allows the passage of nutrients from the aqueous humor to the stroma.
The cornea plays a very important role in vision, since the transparency and uniformity of the layers that form it are responsible for allowing external light to enter in order to transmit it to the retina and generate vision. For this reason it is considered one of the lenses that form the optical system of the eye.
FUNCTIONS OF THE CORNEA
The cornea has two functions:
- It functions as a shield for the eye, protecting it from dust, bacteria and other harmful substances. The cornea shares this function of protecting the eyelids, tears and sclera (the white part of the eye).
- It controls the focus of light entering the eye. In fact, it is the first of the lenses that completes the optical system and is responsible for two-thirds of the refractive power (focusing) of the eye.
In addition, corneal transparency, as mentioned above, is one of the most important characteristics of the cornea. Corneal transparency can be affected by injuries that can be caused by:
→ Chemical injury: by toxic liquid entering the eyes.
→ Abuse or misuse of contact lenses.
→ Diseases caused by fungi, bacteria or viruses.
DISEASES THAT DAMAGE THE CORNEA
- Blepharitis is an infectious disease of the eyelids caused by damage to the Meibomian glands, which are responsible for lubricating the surface of the eye and preventing condensation. Eyes with blepharitis show poor corneal hydration because these glands are blocked.
- Corneal ulcer, as the name implies, refers to changes on the surface of the cornea.
- Conjunctivitis is an infection of the conjunctiva, the mucous membrane that lines the inside of the eyelid. This can also spread and affect the cornea, thus impairing vision.
- Corneal opacification is a disease in which the cornea loses its natural transparency and becomes opaque. This affects human vision because light cannot pass through the eye properly and reach the eye. This can lead to disease, injury or inflammatory processes.
- Dry eye means that the lacrimal system cannot protect the surface of the eye from oil and moisture. It is characterized by foreign body sensation, red eyes, watery eyes and dry eyes.
- Keratitis is an eye disease that can be caused by dehydration, bacterial infection, bacterial infection or, for example, excessive sun exposure.
- Keratoconus is a common type of keratectasia or corneal ectasia, a degenerative disease that causes progressive degenerative changes of the corneal surface. It can grow in one or both eyes at the same time, although it is usually bilateral. As the disease progresses, the cornea becomes abnormally shaped.
CORNEAL TRANSPLANT
A corneal transplant is a procedure in which a diseased cornea is replaced with a healthy cornea from a donor.
The surgery is performed when there is opacity or any disease that affects the transparency of the cornea.
It can have many causes, such as diseases, trauma, dystrophies, degeneration, changes in the nucleus after cataract surgery, such as large corneal opacities. In these cases a procedure called keratoplasty is performed, which consists of replacing the damaged cornea with a healthy cornea.
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