Editing Stimulus modality (section)

===Tests===
Some common tests that measure visual health include [[visual acuity]] tests, refraction tests, [[visual field test]]s and colour vision tests. Visual acuity tests are the most common tests and they measure the ability to bring details into focus at different distances. Usually this test is conducted by having participants read a map of letters or symbols while one eye is covered. Refraction tests measure the eye's need for glasses or [[corrective lenses]]. This test is able to detect whether a person may be [[nearsighted]] or [[farsighted]]. These conditions occur when the light rays entering the eye are unable to converge on a single spot on the [[retina]]. Both [[refractive errors]] require corrective lenses in order to cure blurriness of vision. Visual field tests detect any gaps in peripheral vision. In healthy normal vision, an individual should be able to partially perceive objects to the left or right of their field of view using both eyes at one time. The center field of vision is seen in most detail. Colour vision tests are used to measure one's ability to distinguish colours. It is used to diagnose colour blindness. This test is also used as an important step in some job screening processes as the ability to see colour in such jobs may be crucial. Examples include military work or law enforcement.<ref name="vision test">{{cite web|author=Healthwise Staff|title=Vision Tests|url=http://www.webmd.com/eye-health/vision-tests|publisher=WebMD|accessdate=29 July 2012}}</ref>