The Tuebingen “Visual Acuity at...


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The Tuebingen “Visual Acuity at different levels of Contrast and Ambient Luminance” (VA-CAL) test

Towards a more realistic measurement of the visual performance of glare-sensitive patients under close to everyday light conditions

The VA-CAL study performed by Julian Hilmers as part of his doctoral thesis in the group Pathophysiology of Vision (Head: Professor Dr. med. Zrenner) at the Institute for Ophthalmic Research at the University of Tübingen aims to determine visual acuity as a function of different contrast and luminance conditions.

Currently, the clinical visual acuity test is only performed at a specific luminance (usually between 80-320 cd/m²) and with a maximum contrast of the optotype, which does not reflect the daily conditions. On cloudy days and even more on sunny days, the ambient luminance significantly exceeds the specified luminance for the visual acuity test. The clinically measured value therefore does not reflect the visual acuity during daily activities. Therefore, especially in glare-sensitive patients like completely color blind people, which have a rare hereditary visual disorder affecting the cone photoreceptors called achromatopsia, the visual acuity determined in these artificial conditions is often overestimated and higher than the patients feel in their daily lives.

The study thus aims to measure the visual acuity for different luminance and contrast conditions of everyday life to create a more reliable description of the visual performance and which might result in a clinical parameter valuable for clinical studies like the currently in Tuebingen conducted gene therapy for achromatopsia.  Also, the benefit of edge filters, which filter out part of the short-wave light from the light spectrum, objectively examined for their advantages on visual acuity, especially for glare-sensitive patients.

The study is supported by the Achromatopsie Selbsthilfe e. V.


Dr. Torsten Strasser
Institute for Ophthalmic Research
University of Tübingen
Elfriede-Aulhorn-Strasse 7
D-72076 Tübingen,

Phone: +49 7071 29 8 7793
E-mail: torsten.strasser[at]