The normal eye works like a colour video camera. The iris (coloured part) acts as the diaphragm of the "camera", regulating the amount of light reaching the inside of the eye.
The clear window of the eye (cornea) acts with the lens inside the eye to bend (refract) light rays and bring them to a point focus on the retina. The retina is a thin layer of nerve tissue at the back of the eye that is sensitive to light, like a photographic film. The image formed on the retina is converted into nerve signals that are sent via the optic nerve to the brain.
With eyes that have myopia or short-sightedness, distant objects appear blurred while near objects may be seen clearly.
Light entering the eye is bent or refracted too much for the length of the eye and comes into focus in front of the retina. This is because the ability of the cornea and lens to refract light is too great for the length of the eye.
Myopia typically starts in your teens but occasionally earlier or later in life. It typically stabilises in your twenties. Myopia is the most common vision complaint treated with LASIK.
With eyes that have hyperopia (hypermetropia) or long-sightedness, near objects are more blurred than distant objects. Light entering the eye is not bent or refracted enough for the length of the eye and light comes to a focus behind the retina.
Young people with hyperopia can usually see quite well without glasses but may need reading glasses. As we age hyperopia becomes more of a problem, starting to affect distance as well as near vision. Dr Kent has been treating hyperopia since 1997. He has extensive experience with hyperopic LASIK.
Astigmatism is where the curvature of the cornea is different horizontally compared to vertically. The surface of the cornea is shaped like the side of an egg instead of a round ball. This difference in curvature of the cornea causes light to focus at more than one point inside the eye resulting in blurred vision at all distances.
Astigmatism often accompanies myopia or hyperopia and is corrected at the same time with the excimer laser