Luminance Effects on Visual Acuity and Small Letter Contrast Sensitivity

The purpose of this study was to evaluate the effects of luminance on visual acuity (VA) and small letter contrast sensitivity (SLCS). Computer-generated letter charts were used to measure VA and SLCS [6/7.5 (20/25) Snellen equivalent] as a function of stimulus luminance. Letter size (VA) and contrast (SLCS) were varied in equal logarithmic steps, making the task and scoring procedure comparable for the two types of measurement. Both VA and SLCS decreased with decreasing luminance, but the effect was far greater in the contrast domain. Reducing luminance from 116 cd/m2 to 0.23 cd/m2 produced a 3 x reduction in VA, but a 17 x reduction in SLCS. The greater sensitivity of SLCS to luminance endured even after correction for greater measurement variability. SLCS is a sensitive approach for detecting resolution loss undisclosed by standard measures of VA. It may be useful for monitoring visual loss from light attenuation in early cataracts, and for detecting subtle resolution loss from neural or pathologic factors in ocular and neuro-ophthalmologic disease.

[1]  F. E. Sucs,et al.  Contrast sensitivity in retinitis pigmentosa at different luminance levels , 1992 .

[2]  I L Bailey,et al.  New Design Principles for Visual Acuity Letter Charts* , 1976, American journal of optometry and physiological optics.

[3]  R. L. de Valois,et al.  Psychophysical studies of monkey vision. 3. Spatial luminance contrast sensitivity tests of macaque and human observers. , 1974, Vision research.

[4]  I. Bodis-Wollner,et al.  Visual contrast sensitivity , 1988, Neurology.

[5]  J E Sheedy,et al.  Visual Acuity and Chart Luminance , 1984, American journal of optometry and physiological optics.

[6]  Wilson S. Geisler,et al.  The physical limits of grating visibility , 1987, Vision Research.

[7]  R. Haber,et al.  Visual Perception , 2018, Encyclopedia of Database Systems.

[8]  Angela M. Brown,et al.  Visual acuity of human infants at scotopic, mesopic and photopic luminances , 1987, Vision Research.

[9]  J. Rabin,et al.  Optical defocus: differential effects on size and contrast letter recognition thresholds. , 1994, Investigative ophthalmology & visual science.

[10]  S. Shlaer.  THE RELATION BETWEEN VISUAL ACUITY AND ILLUMINATION , 1937, The Journal of general physiology.

[11]  Denis G. Pelli,et al.  THE DESIGN OF A NEW LETTER CHART FOR MEASURING CONTRAST SENSITIVITY , 1988 .

[12]  H. Barlow.  Temporal and spatial summation in human vision at different background intensities , 1958, The Journal of physiology.

[13]  D. H. Kelly.  Visual response to time-dependent stimuli. I. Amplitude sensitivity measurements. , 1961, Journal of the Optical Society of America.