The part of an eye examination that determines whether there is any reduction in the ability to see. Most vision tests (for example the Snellen chart) are tests of visual acuity. In this type of test, a device called a phoropter is used to hold different lenses in front of each eye. The lenses in the phoropter are changed until the letters near the bottom of the Snellen chart can be read. Tests of visual field may also be performed to assess disorders of the eye and the nervous system. Refraction tests can detect hypermetropia, myopia, or astigmatism; the effect of lenses on movements of light reflected from the eye is observed to calculate the corrective glasses or contact lenses needed. If presbyopia is suspected, close-reading tests are used to assess accommodation.
Vision tests |
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