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Cornea Transplant
A cornea transplant (keratoplasty) is a surgical operation to remove all or part of a damaged cornea and replace it with healthy donor corneal tissue.
A cornea transplant is often referred to as keratoplasty or a corneal graft.
A cornea transplant can be used to improve sight, reduce pain and treat severe infection or damage.
One of the most common reasons for a cornea transplant is a condition called keratoconus, which causes the cornea to change shape.
Most cornea transplant procedures are successful. But as the all other types of surgeries, cornea transplant also carries a small risk of complications, such as rejection of the donor cornea, infection and further vision problems.
So what is the Cornea?
The cornea is a transparent and curved tissue located at the front of the eye that covers the iris, pupil and anterior chamber which refracts light to enter and protect the eye from external factors.
The anterior surface of the cornea is the primary refractive component of the eye (the other refractive component is the lens). The cornea and lens ensure that the light from the external environment is effectively focused on the retina. The refractive power of the cornea is not variable, whereas the refractive power of the lens is variable. In animals, the cornea is found in eyes that evolutionarily contain a lens and/or iris. In humans, it is an oval structure that forms 1/6 of the outer surface of the eye. Measured from the outside, it has a horizontal diameter of approximately 12.6 mm and a vertical diameter of approximately 11.7 mm. Its thickness is 0.5 mm in the middle and 1.2 mm in the edges.
The cornea has to be transparent for clear diffraction of light. Therefore, it does not contain blood vessels in its structure. Oxygenation and nutrition of the cornea is provided by tear secretion on the outside and intraocular visual fluid on the inside.
Since the cornea contains many nerve fibers in its structure, it is very sensitive to external factors. It protects and maintains the health of the cornea with its nerve fibers, blink reflex and supportive properties. Since the cornea is embryologically derived from ectoderm like hair, nails and skin, it is constantly renewed.
Corneal epithelium: This layer is the outermost layer of the cornea, it consists of five layers of cells, the cells located at the bottom and the cells in the limbus surrounding the cornea proliferate and move upwards to replace the old cells, so the corneal epithelium is renewed approximately every two weeks.
Bowman's membrane: It is not actually a membrane in the real sense, it is formed as a result of irregular compression of collagen fibers. Epithelial cells are firmly attached to Bowman's membrane, providing structural support to the cornea.
Corneal stroma: It is a transparent structure that forms the thickness of the cornea, consists of about 100 layers formed by regularly arranged collagen fibers, cells called keratocytes are sparsely contained in it. When this layer is damaged, healing often leads to loss of transparency and/or corneal curvature changes, negatively affecting vision.
Desme membrane: It is a basement membrane secreted by corneal endothelial cells. After damage or diseases, corneal endothelium is damaged and edema develops in the cornea.
Dua's layer: Dua's layer is a newly found layer and is a strong membrane on the cell-free desme with a fibrinoid tissue
Corneal endothelium: The innermost layer of the cornea, composed of hexagonal cells arranged in a single layer. The cells are adhered to each other by tight junctions, functioning as a semi-permeable membrane. Thanks to the pump enzymes located on the lateral surfaces of the cells, the water content of the corneal stroma is kept constant. The name endothelium is actually used incorrectly for these cells. These cells are in contact with the intraocular fluid, not with the blood or lymph fluid, and are of different origin from the vascular endothelium in terms of embryological origin.
Corneal Diseases
Like all living tissues, the cornea can be affected by all disease-causing causes. These diseases can be congenital or acquired. The shape, transparency and metabolism of the cornea may deteriorate after some congenital diseases, for example, the cornea may be smaller than it should be congenitally, this situation is called microcornea.
A significant part of acquired diseases of the cornea develop after infection by different microorganisms, corneal infection can be caused by viruses, bacteria, fungi or protozoa, corneal infections are called keratitis. The cornea can be affected by autoimmune diseases, some of these autoimmune diseases only specifically affect the cornea and its surrounding tissues, while some systemic autoimmune diseases may also affect the cornea, for example, rheumatoid arthritis, an autoimmune disease, may threaten corneal health by causing dry eye syndrome.
Some different systemic diseases or systemic infections may also affect the cornea, for example, diabetes, a systemic disease, may cause basement membrane thickening or nerve damage and non-healing epithelial openings.
The cornea can also be affected by allergic diseases, for example, vernal conjunctivitis, a type of allergic conjunctivitis, can cause damage to the cornea. There are also some dystrophic diseases specific to the cornea, many of which show familial inheritance, keratoconus is a dystrophic disease manifested by thinning of the cornea and associated advanced astigmatism and visual impairment. Some degenerative diseases can also be seen in the cornea due to aging and ultraviolet (ultraviolet) radiation damage.
Since the cornea is located in the outermost part of the eye, it can be traumatized frequently, these traumas can be mechanical, thermal, or chemical, radiation can affect the cornea as it affects all tissues. After corneal traumas, the integrity of the eyeball may be impaired, which is a condition that needs to be treated urgently.
The most important thing to do after the eye comes into contact with acid or alkaline chemicals is to immediately wash the eye and surrounding tissues with plenty of water and apply to the nearest eye clinic. In some cases, the eye may need to be washed with liters of water.
* The content of the page is for informational purposes only, please consult your doctor for diagnosis and treatment.
