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The SKILL Card. An acuity test of reduced luminance and contrast. Smith-Kettlewell Institute Low Luminance
G Haegerstrom-Portnoy1, J Brabyn, M E Schneck
1Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115, USA.
Purpose:
To design and evaluate a new vision test that combines low contrast and reduced illumination to stress the visual system and be sensitive to subtle alterations in function.
Methods:
A simple new clinical test, the Smith-Kettlewell Institute Low Luminance (SKILL) Card, is designed to measure spatial vision under conditions of reduced contrast and luminance using normal office lighting. The SKILL Card consists of two near acuity charts mounted back to back. One side has a chart with black letters on a dark gray background designed to simulate reduced contrast and luminance conditions. The other side has a high-contrast, black-on-white letter chart. The SKILL score is the acuity loss (number of letters) between the light and dark sides.
Results:
Age norms for a large normal population have been established and show that test scores increase with age, particularly after age 50. Repeatability is as good as that of standard Snellen acuity. The SKILL score is affected minimally by blur, but it is affected by large variations in light level. SKILL scores are sensitive to the presence of visual disease such as "recovered" optic neuritis.
Conclusions:
The SKILL card allows quick, reliable measurement of the effect of reduced luminance and contrast on acuity SKILL scores are not correlated with other vision measures in patients with optic neuritis, which shows that the SKILL card measures a different dimension of vision function than existing clinical tests.