The Freiburg Visual Acuity test--automatic measurement of visual acuity
The Freiburg Visual Acuity test is an automated procedure for self-administered measurement of visual acuity. Landolt-Cs are presented on a monitor in one of eight orientations. The subject presses one of eight buttons, which are spatially arranged on a response box according to the eight possible p...
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| Published in: | Optometry and vision science Vol. 73; no. 1; p. 49 |
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| Main Author: | |
| Format: | Journal Article |
| Language: | English |
| Published: |
United States
01.01.1996
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| Subjects: | |
| ISSN: | 1040-5488 |
| Online Access: | Get more information |
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| Summary: | The Freiburg Visual Acuity test is an automated procedure for self-administered measurement of visual acuity. Landolt-Cs are presented on a monitor in one of eight orientations. The subject presses one of eight buttons, which are spatially arranged on a response box according to the eight possible positions of the Landolt-Cs' gap. To estimate the acuity threshold, a best PEST (best Parameter Estimation by Sequential Testing) procedure is used in which a psychometric function having a constant slope on a logarithmic acuity scale is assumed. Measurement terminates after a fixed number of trials. With computer monitors, pixel-discreteness artifacts limit the presentation of small stimuli. By using anti-aliasing, i.e., smoothing of contours by multiple gray levels, the spatial resolution was improved by a factor of four. Thus, even the shape of small Landolt-Cs with oblique gaps is adequate and visual acuities from 5/80 (0.06) up to 5/1.4 (3.6) can be tested at a distance of 5 m. |
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| Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
| ISSN: | 1040-5488 |
| DOI: | 10.1097/00006324-199601000-00008 |