Citation

Bach M. Ophthalmologe 1995; 92(2): 174-178.

Vernacular Title

Der Freiburger Visustest. Automatisierte Sehscharfebestimmung.

Affiliation

Universitäts-Augenklinik Freiburg i. Br.

Copyright

(Copyright © 1995, Holtzbrinck Springer Nature Publishing Group)

DOI

unavailable

PMID

7780276

Abstract

The Freiburg Visual Acuity Test is an automatic computerized 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 according to the eight possible positions of the Landolt-C's gap. To estimate the acuity threshold, a best-PEST procedure is employed, assuming a psychometric function with a constant slope on a logarithmic acuity scale. The discreetness artifacts in computer monitors limit the presentation of small stimuli. By anti-aliasing (smoothing of contours by gray-shading), the spatial resolution was improved by a factor of four, such that the shape of Landolt-Cs with oblique gaps is adequate and visual acuities from 0.06 up to 3.6 can be tested at a distance of 5 m.

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