Your Complex Cornea – More Than Meets the Eye
You can really amaze your friends at parties with this information, and it helps you to make an informed decision on deciding if Laser Eye Surgery is right for you.
How the Cornea Works in Sight
The eye is set into a bony shell, called the orbit, and surrounding by soft fatty tissue. The eye’s movement are controlled by extraocular muscles, so you can look around in various directions without having to turn your whole head.
The glass-like cornea is the outermost part of the eye; it’s the bit that gets easily irritated by dust. It’s about a half a millimetre thick and about 12mm across, and is basically a section of the sphere that makes up the entire eyeball.
It’s the part that is responsible for refracting most of the light that enters the eye, so it’s hugely important in your ability to focus properly. Even the tiniest change in the shape of your cornea makes a big difference in the resulting focus.
This is why most laser eye surgery is Refractive Surgery, as it involves changing the shape of the cornea to treat focusing or refractive errors.
Layers of the Cornea
The cornea actually has several layers to it, called the epithelium, stroma and endothelium. The Bowman membrane lies between the epithelium and the stroma and the Descemet layer between the stroma and the endothelium.
This is great party trivia-although you might find yourself standing alone in a corner. With your cornea chat and your drink.
Self-Healing Epithelium Layer
The epithelium is made up of lots of cells-5 layers of them to be exact- which have the ability to multiply, and is covered by the tear film.
Because of its ability to regenerate itself, it’s essentially self-healing and usually fixes itself within a couple of days, which is very handy for eye surgery patients.
Strong Stroma Layer
The stroma, the main layer of the cornea, takes up most of the space and is made of collagen fibres, which form lamellar sheets like the pages of a notebook.
It’s the packing and spacing of these collagen fibres that provides the transparency of the eye, and the stromal cells (keratocytes) can’t reproduce themselves, and don’t have nerve endings so feel no pain. They give your eye its strength and its dome-like shape, and that’s why refractive surgery is generally performed on this layer.
Important Role of Thin Endothelium Layer
The endothelium, which is the innermost layer of the cornea, looks like a transparent honeycomb under a microscope. It’s only one layer of cells, but it plays a vital function in keeping the cornea transparent; there is a balance of liquid in the cornea and this is maintained by pumping excess liquid by means of the endothelium.