Contact Lens Update

Often referred to as the clear front part of the eye, this tissue serves to bend light and helps focus light rays onto the retina. The cornea accounts for approximately 60% of the refractive power of the eye (the lens accounts for approximately 30-40%) and contains several layers that functions to help maintain transparency to light.
The outermost layer is called the corneal epithelium, it is a protective barrier against the outside elements and prevents entry of micro-organisms and serves a small role in dehydrating the corneal stroma. It also contains glycoproteins that interact with the tear film.
The corneal stroma lies beneath the corneal epithelium and is constructed of collagen arranged in a highly regular fashion. Disruption of fibre regularity, either as a result of trauma or edema will result in decreased corneal transparency.
The corneal endothelium is the inner most layer of the cornea and its main function is to remove water from the stromal layer. In young patients, endothelial cells are arranged in an organized hexagonal pattern, but with aging, the arrangement becomes irregular as the number of endothelial cells decrease and endothelial pump function begins to decline.