The eye is made up of various parts which determine what and how we see. Before we can understand anything about LASIK surgery and what it does to correct visual disorders, it is important to know the different parts of the eye and how the eye sees. When light enters the eye, it first passes through the cornea. This transparent layer of the eye is the region where 70 percent of light entering our eyes is focused or refracted.
Extending outwards and surrounding the cornea is the sclera, the white opaque coat that makes up most of the eye ball. Its purpose is to shape the eyeball with its thickness and strength. Next, light rays pass through the lens, which is responsible for about 30 percent of the focusing. The lens does this by changing its shape – becoming flatter and thinner or rounder and thicker – with the help of specialised muscles and ligaments in the eye. The function of the lens is to adjust the focus of light onto the retina. This is referred to as accommodation.
The choroid or middle layer of the eye, is found between the sclera and retina. This layer contains numerous blood vessels, and supplies blood and nourishment to the tissues in the eye. The images of what we see are projected onto the retina. The retina contains numerous light-sensitive receptors called rods and cones, which are responsible for giving colour and contrast to our vision. Most of the light rays are focused onto a small part of the retina called the fovea, which is sometimes referred to as the “yellow spot”. The fovea contains the highest density of light receptors. When nerve cells in the retina are stimulated by light, they send nerve impulses to the brain via the optic nerve. This allows us to perceive images.
LASIK surgery involves re-shaping the cornea to correct visual disorders such as short-sightedness, long-sightedness and astigmatism. Click here to learn more about LASIK surgery.