VISION IS OURMISSIONDesign, build and test a digital vision acuity exam to provide an approximate prescription for corrective lenses where the program uses calculation for determining letter height based on user distance.
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Eye exams are expensive and difficult to arrange in areas where professionals are in high demand. Ophthalmologists are often overbooked, which leads to long wait times for appointments.
QUALITY TESTING
SnellTech not only offers a digital exam but calibration solutions to ensure reliable results. Why choose the SnellTech headset?
- Ensures more accurate results with Snelltech test
- Adjustable head strap offers a comfortable fit
- 4 different distance calibration settings: 2ft, 3ft, 4ft, 5ft
- Simple assembly and durable, lightweight construction
Get your Visual Acuity
Letter charts are not only used to measure visual acuity, they are also used as targets for subjective refraction. This is the main reason distance acuity is measured more often than near acuity. At a long distance, accommodation is relaxed.
At a longer test distance, the effect of small changes in the subject’s position is less important and can be ignored. As today’s exam lanes often are smaller than 20 feet (6 meters), charts are often designed for shorter distances. This is no problem for visual acuity measurement, as long as the actual test distance is accurately accounted for.
Use the SNELLEN Test
It is a persistent urban legend that 20/20 would represent normal, average or even perfect vision. This is not so. Snellen deliberately chose his reference standard (5 min of arc) as a size that is “easily recognized by normal eyes.” Thus, almost all normal eyes will equal or exceed the reference standard. If 20/20 equaled average acuity, half of the population would fall short of 20/20, since that is the definition of average.
Visual acuity values are understood best by the following simple rule. On a Snellen chart we determine the line that the person can just recognize. If that line is twice as large as the reference standard (20/20), we state that that person’s MAgnification Requirement (MAR) is 2x. If the MAgnification Requirement is 2x, the visual acuity is 1/2 (20/40). Similarly, if the MAgnification Requirement (MAR) is 5x, the visual acuity is 1/5 (20/100); if MAR = 10, visual acuity = 1/10 (20/200), and so on.