Refractive Error, also known as refraction error, is a problem with focusing of light on the retina due to the shape of the eye.

The most common types of refractive error are:

•  Near-sightedness (myopia)
•  Far-sightedness (hypermetropia)
•  Astigmatism
•  Presbyopia

Near-sightedness results in far objects being blurry, far-sightedness result in close objects being blurry, astigmatism causes objects to appear stretched out or blurry, and presbyopia results in a poor ability to focus on close objects. Other symptoms may include double vision (dipplopia), headache and eye strain.

Near-sightedness is due to the length of the eyeball being too long, far-sightedness the eyeball too short, astigmatism the cornea being of different curvetures, and presbyopia ageing of the lens of the eye such that it cannot change shape sufficiently. Some refractive errors are inherited from a person's parents. Diagnosis is by eye examination.

Refractive errors can be corrected by:

Spectacles

•  Single vision lenses and biofocal / multifocal / progressive lenses.



Contact lenses

•  Most lenses are made up of silicone hydrogel. Other materials like Lotrafilcon, Nelfilcon and Phemfilcon.



Intraocular lenses

•  Phakic IOL, PIOL, removal of crystiline lens with IOLI.



Corneal surgical procedures

•  LASIK, PRK, LASEK, RK

Hypermetropia

Myopia