Glossary of Terms
Photo: Photo means light. The excimer laser uses ultra-violet laser light to reshape the cornea, hence the term photo.
Refractive is the term used when a ray of light is bent as it passes through a transparent substance. The lens in a camera refracts light so that it is focused on the film and similarly your glasses or contact lenses refract light, allowing you to see more clearly. As the excimer laser reshapes the cornea it changes the cornea's ability to refract light, hence the term refractive.
The term keratectomy means removal of part of the cornea. This is precisely what the excimer laser does to reshape the cornea.
Light rays are refracted by the cornea and the lens in such a way that the focal point is in front of the retina. Distant objects appear out of focus. Depending on the degree of myopia, near objects appear in sharp focus.
Light rays are refracted by the cornea and the lens in such a way that the focal point is behind the retina. Depending on the extent of the farsightedness, objects which are close, and even distant ones in some cases, appear out of focus.
Through the increasing inflexibility of the lens, the light rays cannot be focused on the focal point of the retina. As a result, objects appear out of focus.
Astigmatism is a condition where the vertical curve of the cornea is not equal to the horizontal curve of the cornea. This is best visualised by imagining a soup spoon next to a dessert spoon. The curve of the soup spoon in the direction of the handle is the same as the curve from side to side and is therefore part of a perfect sphere-like a soccer ball-so it represents no astigmatism. A dessert spoon on the other hand has a flatter curve in the direction of the handle compared to the steeper curve from side to side. This makes it look like a slice cut off a rugby ball and therefore represents astigmatism because the two curves are different.
Laser:(Light Amplification by Stimulated Emission of Radiation):
Laser light is a pure wavelength (colour) and highly concentrated. Thus it is of very high energy.
In-situ means within the structure or substance.
Mileusis means the dissolving of tissue, and kerato indicates the cornea. Thus, it is the dissolving of the corneal tissue.