Our cornea is the tissue with higher density of nerve endings of all those that make up our body. It is in the most external part of our eyes and has, on the one hand, a optical function and, on the other, mission to protect the rest of ocular tissues. In relation to all of them is the structure with greater optical power , despite the fact that its focus is fixed (unlike, for example, the adjustable approach of the lens). Its main characteristic is that it's transparent so as not to pose any obstacle to the light that penetrates into the interior of the eye. For that reason lacks blood vessels . As for its form, it is aspheric , that is to say, spherical in its central part but flattened in the external zones.
But, if it lacks blood vessels, where does it get the necessary supply of nutrients and oxygen? The answer has to do with our tears , on the one hand (the previous one), and with the aqueous humor on the other (the later). And once we know what is the cornea , let's proceed to focus on how the parts work what make it up
What is the cornea and how does it work: everything you need to know
Parts of the cornea
Regarding your protective function , prevents the iris and lens from being affected by the outbreak of external elements such as germs or dirt. And the first barrier that any harmful agent finds is the corneal epithelium , the external impermeable layer that prevents the passage of tear fluid to the inner part of the eye.
The next part of the cornea is the Bowman Membrane , formed by small collagen fibers (not by cells) and only present in primates. Besides assuming another extra protective layer, it provides stability to the structure of the cornea, which helps maintain its shape. Unlike the epithelium, which stands out for its rapid regeneration, in Bowman's Membrane any lesion results in a scar.
Behind is the stroma , which is composed of more collagen fibers, but also has cellular structures (keratocytes) and a fundamental substance. The keratocytes are responsible for accumulating and interlacing in the event of any damage to the stroma, which causes whitish scars that can cause loss of vision of greater or lesser importance.
In this journey through the different strata of the cornea we now arrive at a newly discovered layer that is named after its discoverer, Professor Harminder Dua. We talk about the Dua coat , which, despite its very small thickness, is extremely resistant and is expected to assume in itself a key advance with regard to improving cornea transplants .
Continuing towards the inner part of the eye we find the Membrane of Descemet , consisting of more collagen fibers and proteins, and, beyond that, with endothelium or posterior epithelium , a semipermeable layer of polygonal cells that allows the passage of nutrients present in the aqueous humor.