Purpose
Contrast sensitivity function is decreased in many disease entities notably: cataract, age related macular degeneration and glaucoma. It is also lowered in individuals that undergo kerato-refractive surgery procedures. Traditional contrast sensitivity tests printed on charts are limited in the fact that a certain working distance is needed and are prone to degradation due to use. The electronic M&S Smart System contrast sensitivity testing unit provides the flexibility to use at variable distance and provides better resolution capabilities especially at lower contrast due to the visual display system. The purpose of the study was to evaluate the short-term repeatability and use of Landolt C contrast sensitivity function test in ocular healthy and in individuals with decreased visual function.
Methods
Twenty six individuals were tested twice using the Landolt C-CSF test of the M&S Smart System contrast sensitivity testing system. The mean age of the study participants was 37.3 years (SD 15). The Landolt C-CSF was performed for 20/20, 20/40 and 20/80 and all measurements were obtained viewing the chart binocularly at a distance of nine feet. Repeatability was assessed using Altman and Bland plots and 95% limits of agreement were calculated. The difference in measurements of first and repeat measurements was assessed using paired samples t-test.
Results
Table 1 below provides the mean of first and second measurements of obtained data using the Landolt C contrast sensitivity function test and the limits of agreement at different acuities. Overall the contrast sensitivity peak measured as percent contrast was very repeatable at different visual acuity levels with average difference in percent contrast being not significantly different in all three acuity levels (paired samples t-test p value 0.8, 0.9 and 0.9 respectively).
Conclusions
The Landolt C-CSF test of the M&S Smart System contrast sensitivity testing system is repeatable and provides data that can be useful in measuring contrast levels. Further tweaks may be done to provide area under log CSF from the various peak contrast sensitivity tested.