In this case, the focus of the eyes can be corrected with an external lens, such as glasses or contact lenses, or through surgery.
Visual perception is the ability to interpret information and surroundings from visible light reaching the eye.
The various physiological components involved in vision are referred to collectively as the visual system, and are the focus of much research in psychology, cognitive science, neuroscience and molecular biology.
[3] The human eye's non-image-forming photosensitive ganglion cells in the retina receive the light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock.
In the term "20/20 vision" the numerator refers to the distance in feet from which a person can reliably distinguish a pair of objects.
Intraocular lenses are surgically implanted most commonly after cataract removal, but recently for purely refractive purposes.
Modern glasses are typically supported by pads on the bridge of the nose and by temple arms placed over the ears.
Lenses now have a slight bluish tint which is a thin UV coating; this reduces glare and cornea damage much like a pair of sunglasses.
[citation needed] Photorefractive keratectomy (PRK) and Laser-Assisted Sub-Epithelial Keratectomy (or Laser Epithelial Keratomileusis[7]) (LASEK) are laser eye surgery procedures intended to correct a person's vision, reducing dependency on glasses or contact lenses.
The first LASEK procedure was performed at Massachusetts Eye and Ear Infirmary in 1996 by ophthalmologist, refractive surgeon, Dimitri Azar.
[8] The procedure was later popularized by Camellin, who coined the term LASEK for laser epithelial keratomileusis.
Insertion of an intraocular lens for the treatment of cataracts is the most commonly performed eye surgical procedure.