CORNEA

CORNEA

The cornea has unmyelinated nerve endings sensitive to touch, temperature and chemicals; a touch of the cornea causes an involuntary reflex to close the eyelid . Because transparency is of prime importance ,the cornea does not have blood vessels and it receives nutrients via diffusion from the tear fluid at the outside and the aqueous humour at the inside and also from neurotrophins supplied by nerve fibres that innervate it. It borders with the sclera by the corneal limbus.

Size:

In humans, the cornea has a diameter of about 11.5 mm and a thickness of 0.5–0.6 mm in the center and 0.6–0.8 mm at the periphery. Transparency, avascularity, and immunologic privilege makes the cornea a very special tissue. The cornea is the only part of a human body that has no blood supply; it gets oxygen directly through the air.In humans, the refractive power of the cornea is approximately 43 Diopters.

Treatment and management

Surgical procedures
Various Refracive Eye Surgery techniques change the shape of the cornea in order to reduce the need for corrective lenses or otherwise improve the refractive state of the eye. In many of the techniques used today, reshaping of the cornea is performed by photoablation using the excimer laser.

If the corneal stroma develops visually significant opacity, irregularity, or edema, a cornea of a deceased donor can be Transpalanted. Because there are no blood vessels in the cornea, there are also few problems with rejection of the new cornea.
There are also synthetic corneas (keratoprostheses) in development. Most are merely plastic inserts, but there are also composed of biocompatible synthetic materials that encourage tissue ingrowth into the synthetic cornea, thereby promoting biointegration.

Non-surgical procedures

ORTHOKERATOLOGY is a method using specialized hard or rigid gas-permeable contct Lenses to transiently reshape the cornea in order to improve the refractive state of the eye or reduce the need for eyeglasses and contact lenses.