Cornea

The cornea of the eye is built of several different layers (from outside inward): epithelium, basal layer, Bowman's layer, stroma, Descemet's membrane and endothelium. The cornea contributes 2/3 of the eye's optical power (40D out of 60D). The cornea has a spherical shape in its central third, which has a diameter of about 4mm. The thickness of the cornea in the central zone is the thinnest and measures 0.5mm, compared with the periphery, which reaches a thickness of up to 1.0mm.

The epithelial layer (Corneal Epithelium) and the basal layer (Basal Lamina)

The anterior surface of the cornea is covered by nonkeratinized stratified squamous epithelium. The basal layer is columnar and attached to the lamina by hemidesmosomes. Above the basal layer there are several layers of polygonal cells (wing cells) connected to one another by zonules, forming a membrane layer for the epithelium.

News and articles in the field of cornea

Pterygium surgery: side effects and complications

December 24, 2021

Are there side effects to pterygium surgery, and why? Many patients ask me whether pterygium surgery has side effects. Does pterygium surgery have complications? Well, pterygium surgery is a procedure

Corneal replacement surgery

January 30, 2022

What is corneal replacement surgery? Corneal replacement surgery (corneal transplant) is a surgery in which the cornea is replaced with corneal tissue from a deceased donor, and it is one of the most common transplants performed. What is the cornea and why is replacement surgery needed

Eye drops for dryness

June 13, 2023

What is dry eye? The outer surface of the eye is constantly moistened by tears. This moisture is essential for keeping the eye's surface clean of debris and bacteria, which makes it essential for maintaining eye health.

The epithelial cells migrate in two planes

Inward -> outward:Migration from the deep layers to the superficial layers.

Peripheral -> central:Migration from the limbus layer (corneal limbus) toward the center. The stem cells are located in the limbus area, so significant damage to this area will lead to chronic defects in the corneal epithelium.

Bowman's layer

Beneath the basal layer there is a membrane named after Bowman (Bowman's membrane). It is in fact the outermost layer of the stroma of the cornea. Damage to this area leads to scarring in the cornea of the eye.

The stroma layer of the cornea (Corneal Stroma)

The stroma of the cornea makes up 90% of the cornea's thickness. The fibrils of the cornea are identical in size and precisely arranged so that the cornea remains transparent. 5% of the stroma's volume is occupied by keratocytes, which resemble fibrocytes; they too are arranged in a way that allows the cornea to remain transparent.

Descemet's membrane

Descemet's membrane constitutes the basal layer of the endothelial layer of the cornea. This layer thickens over time (from 4 micrometers at birth to 12 micrometers in adults).

The endothelium of the cornea

The corneal endothelium is built of a single layer of cells. The cell density is about 3000 cells per square millimeter.
An ophthalmologist skilled at this can identify the characteristics of these cells with the help of a specular microscope in the slit lamp. The number of cells in the endothelial layer decreases over the years. These cells are responsible for removing water from the stroma of the cornea and maintaining its transparency. Damage to this layer as a result of surgeries or congenital diseases such as Fuchs Endothelial Dystrophy will lead to edema in the stroma layer, impaired transparency of the cornea and ultimately to impaired vision.