Synonyms for ametropic or Related words with ametropic
Examples of "ametropic"
amblyopia, is a medical condition in which the retina cannot focus on the image of a distant object, a condition often described as reduced visual acuity. This is due to large uncorrected refractive errors in the patient's optic system of the eyes. Astigmatism is one of the most frequent causes of
An eye that has refractive error when viewing distant objects is said to have "ametropia" or be "
". This eye cannot focus parallel rays of light (light from distant objects) on the retina, or needs accommodation to do so.
Visual acuity depends upon how accurately light is focused on the retina, the integrity of the eye's neural elements, and the interpretative faculty of the brain. "Normal" visual acuity (in central, i.e. foveal vision) is frequently considered to be what was defined by Herman Snellen as the ability to recognize an optotype when it subtended 5 minutes of arc, that is Snellen's chart 6/6 meter, 20/20 feet, 1.00 decimal or 0.0 logMAR. In young humans, the average visual acuity of a healthy, emmetropic eye (or
eye with correction) is approximately 6/5 to 6/4, so "it is inaccurate to refer to 6/6 visual acuity as "perfect" vision". 6/6 is the visual acuity needed to discriminate two contours separated by 1 arc minute- 1.75 mm at 6 meters. This is because a 6/6 letter, E for example, has three limbs and two spaces in between them, giving 5 different detailed areas. The ability to resolve this therefore requires 1/5 of the letter's total size, which in this case would be 1 minute (visual angle). The significance of the 6/6 standard can best be thought of as the lower limit of normal or as a screening cutoff. When used as a screening test, subjects that reach this level need no further investigation, even though the average visual acuity with a healthy visual system is typically better.
Copyright © 2017