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Refractive Errors
What are refractive errors?
The cornea and lens bend or refract light rays so they can be focused on the retina, the nerve layer that lines the back of the eye. The retina receives the picture formed by these light rays and sends the image to the brain through the optic nerve. A refractive error means that the shape of the eye does not allow the light to be properly refracted, making images blurry.
Refractive errors include:
- Myopia (near-sightedness)
Myopia (near-sightedness) occurs when light rays are focused in front of the retina instead of directly on the retina. Nearsighted people have difficulty seeing objects at a distance, such as highway signs, but usually can see up-close for tasks such as reading or sewing. - Hyperopia (farsightedness)
Hyperopia or farsightedness occurs when light rays are not bent enough to focus on the retina. People with hyperopia can sometimes see distant objects very well but may have difficulty seeing close objects. - Astigmatism
Regular astigmatism occurs when light rays are focused at more than one point on the retina. Astigmatism is the most common vision problem. It occurs when the cornea surface is not ideally rounded but is curved more along one axis than the other — that is when the eye is shaped more like the side of a football than a soccer ball. Light entering the eye does not focus symmetrically on the retina. The result is astigmatism, which blurs both near and distance vision. This refractive error may occur in patients who are either myopic (nearsighted) or hyperopic (farsighted). There are various types of astigmatism which include regular, mixed and irregular astigmatism. - Presbyopia
With increasing age, the lens inside of the eyes loses the ability to focus on nearby objects. The problem usually manifests itself around age 40 and can be corrected with bifocals or reading glasses. This is a normal ageing process. - Monovision
Monovision is a method of correcting presbyopia and essentially leaves one eye for near and one eye for distance. This is achieved either through contact lenses or refractive surgery. Contact lenses or glasses may be required for best distance or night vision activities, including driving. This option is not suitable for everyone and a trial period of monovision using contact lenses may help decide if it is right for you.
How are refractive errors treated?
Eye specialists correct or treat refractive errors with glasses, contact lenses or surgery. Refractive surgery is done to correct the refractive error using different options laser eye surgery options, such as:
- Lasik
- Photorefractive keratectomy or PRK
- Phakic intraocular lenses
- Multifocal intraocular lenses
Your eye specialist will recommend the right eye surgery for you.
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