Where is the cornea in the eye

The cornea is a very important part of the eye. If there is a problem with the cornea, the patient's vision will be greatly damaged, and there will even be a risk of blindness. However, many people do not know where the cornea is in the eye. In fact, it is at the front of the eye. This is one of the reasons why the eyes are very fragile, and we must protect our eyes.

The cornea is the transparent front part of the eye, covering the iris, pupil and anterior chamber, and providing most of the eye's refractive power. Combined with the refractive power of the lens, light can be accurately focused on the retina to form an image.

The cornea has very sensitive nerve endings. If foreign objects touch the cornea, the eyelids will close involuntarily to protect the eyes. In order to maintain its transparency, the cornea has no blood vessels and obtains nutrients and oxygen from the outside air, tears and aqueous humor.

The cornea is divided into five layers, from front to back: epithelial cell layer (epithelium), anterior elastic layer (lamina elastica anterior also known as Bowman's membrane), stroma, posterior elastic layer (lamina elastica porterior also known as Descemet's membrane), and endothelial cell layer (endothelium). The epithelial cell layer is about 50um thick, accounting for 10% of the entire corneal thickness, and is composed of 5-6 layers of cells. The epithelium in the peripheral part of the cornea is thickened, and the number of cells increases to 8-10 layers.

In the past, it was believed that the anterior elastic layer was a special membrane. Observation under an electron microscope showed that the membrane was mainly composed of collagen fibers.

The stroma is composed of collagen fibers, about 500um thick, accounting for 90% of the thickness of the entire cornea. The parenchyma layer contains a total of 200-250 lamellar layers that overlap each other. The lamellae are parallel to the surface of the cornea, and the lamellae are also parallel to each other, ensuring the transparency of the cornea. The Descemet's membrane is the basement membrane of the corneal endothelial cells, which can be easily separated from the adjacent stroma and endothelial cells. The Descemet's membrane is strong and resistant to chemical substances and pathological damage. Endothelial cells are a single layer of cells, composed of approximately 500,000 hexagonal cells, 5um high and 18-20um wide. The nucleus is located in the center of the cell, is oval in shape, and has a diameter of approximately 7um.

1. The corneal epithelium is about 50 microns thick and is easily separated from the Bowman's layer. It is composed of 5 to 7 layers of cells, with a total of 3 types of cells: basal cells, wing cells, and flat cells. Epithelial cells are connected by bridge bodies to form a dense plasma membrane. This dense and strong barrier can prevent the invasion of most microorganisms and prevent the fluid and electrolytes in the tears from entering the matrix layer, leaving the cornea in a relatively dehydrated state.