Clearing up refractive errors
Several ocular conditions corrected with glasses or contact lenses can be improved with laser surgery. The type of surgery, whether it's LASIK, LASEK or lens implants, depends on the patients' specific condition and the extent of refractive error. Specifically, these conditions are defined as:
- Astigmatism
Occurs when light is focused in two different places in the eye, causing blurred vision. An astigmatic cornea can be considered oval shaped and not round. 
Hyperopia (farsightedness)
Occurs when light strikes the retina before sharp focus is attained. This is caused by an eye that is too short to properly focus light on the retina and means you have a hard time seeing things up close.
Myopia (nearsightedness)
Occurs when light is focused in front of the retina, caused by an eye that is too long to focus light on the retina properly, or a cornea that is too curved. This means you have a hard time seeing things at a distance.- Presbyopia (age-related impairment)
Occurs when the aging lens becomes less elastic, marked by the need for reading glasses or bifocals usually after the age of 40.
How the eye works
Vision is all about light rays and reflection. Refractive errors can occur when the cornea is not shaped properly or when the eye is too short or too long. As a result, light rays are refracted incorrectly causing focus to occur either behind or in front of the retina. The result is blurred vision in far or near ranges.
The cornea is the clear front covering of the eye where light rays enter. When the cornea is curved properly, light rays are refracted (bent) in angles that allow sharp focus. The pupil is the black portion of the eye that regulates light by expanding or contracting. The iris, or the colored portion of the eye, also helps regulate light and contains much of the muscle structure that controls the pupil's movement. Behind the iris is a crystalline lens that focuses an image to the inner back portion of the eye, called the retina. The retina is responsible for transmitting light pulses through the optical nerve to the brain where the image is interpreted into what we see.
When the process works correctly, vision is considered 20/20. When it does not, there may be refractive errors, a collective term for eye conditions like astigmatism, hyperopia (farsightedness), myopia (nearsightedness) and age-related impairment (presbyopia).
Refractive surgery involves changing the refractive power of the eye, either by reshaping the cornea or replacing the natural lens with a lens implant. This modification will improve the image developed by the brain.