![]() Donders eventually passed on his responsibilities to Snellen because he was very occupied with other disciplines of science like physiology. Donders as he determined vision impairments patients had by having them look at a chart on the wall. The conception of his chart began when Snellen became Donder's first assistant. Although the general concept of the eye chart was introduced during the 1830s by doctors mentioned previously, the most effective chart to test visual acuity at the time was refined in 1862 by Dutch optometrist Herman Snellen. Shortly after, an Austrian doctor, Eduard Jaeger created a chart which tested near vision acuity. German eye doctor, Heinrich Kuehler proposed the first examination in order to test visual acuity. Previous studies led to doctors (worldwide) determining a way in which visual acuity could be examined. Around this time, the knowledge within the field of ophthalmology grew immensely. Although it slowly became clear what the procedure was in order to benefit a patient through his work, there was no uniform exam in order to prove the impairment in someone’s vision. As science progressively improved, reputable doctors within the ophthalmology field like Cornelius Donders began to describe a clear definition as to what should be done in order to improve timeless impairments of a patient's vision. The concept of using eye glasses in order to improve eyesight has been prevalent since the late thirteenth century. Otherwise binocular fusion may be worse that it is supposed to be. It is more important to pass that test, than have perfect binocular vision in Snellen chart, especially for toric contact lenses that may behave differently from glasses. In practice, it is very important to recheck the result using Duochrome test, because it allows to refine the final sphere in refraction. Eye charts do not provide doctors with information on eye diseases such as glaucoma, problems with the retina, or loss of peripheral vision. As previously mentioned, eye charts measure visual acuity. Alternative types of eye charts include the logMAR chart, Landolt C, E chart, Lea test, Golovin–Sivtsev table, the Rosenbaum chart, and the Jaeger chart. The Snellen chart is the most widely used. The smallest symbols that can be reliably identified is considered the person's visual acuity. The person then attempts to identify the symbols on the chart, starting with the larger symbols and continuing with progressively smaller symbols until the person cannot identify the symbols. The chart is placed at a standardized distance away from the person whose vision is being tested. Ophthalmologists, physicians who specialize in the eye, also use eye charts to monitor the visual acuity of their patients in response to various therapies such as medications or surgery. Eye charts are often used by health care professionals, such as optometrists, physicians or nurses, to screen persons for vision impairment. An eye chart, or optotype, is a chart used to subjectively measure visual acuity.
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