THE VALIDITY OF CURRENT CLINICAL-TESTS OF CONTRAST SENSITIVITY AND THEIR ABILITY TO PREDICT READING SPEED IN LOW-VISION

Purpose: Contrast sensitivity (CS) testing using chart tests of CS is becoming increasingly common in low vision assessment, Yet we know lit tle about the validity of these charts, i.e. which region of the spati al frequency spectrum is being measured. In this study we aimed to det ermine the validity of currently available CS charts by comparison aga inst oscilloscope-based CS. We also determined their relative ability to predict reading speed. Methods: CS was measured with five commercia lly available charts and the contrast sensitivity function was determi ned with sinusoidal gratings presented on a Joyce screen using a two-a lternative forced choice staircase technique in 36 observers with low vision and 3 with normal vision. Reading rate was also measured with t he subject reading with his or her own optical low vision aid. Results : The results show that the Pelli-Robson chart and the Cambridge grati ngs are good measures of medium to Low spatial frequencies, as would b e predicted from their design, while the Regan and UW charts correlate d with medium to high frequencies. The Vistech chart was a good predic tor of CS at each spatial frequency. Conclusions: The best chart test of CS depends on which region of the CS curve is of interest. All the charts were good predictors of reading rate.