Visual Performance as a Function of Luminance in Glaucoma: The De Vries-Rose, Weber's, and Ferry-Porter's Law

PURPOSE. To determine whether the De Vries-Rose, Weber's, and Ferry-Porter's law, which describe visual performance as a function of luminance, also hold in patients with glaucoma. METHODS. A case-control study with 19 glaucoma patients and 45 controls, all with normal visual acuity. We measured foveal and peripheral contrast sensitivity (CS) using static perimetry and foveal and peripheral critical fusion frequency (CFF; stimulus diameter 1 degrees) as a function of luminance (0.02 to 200 cd/m(2)). ANOVA was used to analyze the effect of glaucoma and luminance on CS and CFF; analyses were adjusted for age and sex. RESULTS. Foveally, logCS was proportional to log luminance at lower luminances (de Vries-Rose) and saturated at higher luminances (Weber); glaucoma patients had a 0.4 log unit lower logCS than controls (P <0.001), independent of luminance. Peripherally, the difference was more pronounced at lower luminances (P = 0.007). CFF was linearly related to log luminance (Ferry-Porter). Glaucoma patients had a lower CFF compared with controls (P <0.001), with a smaller slope of the CFF versus log luminance curve, for both the fovea (6.8 vs. 8.7 Hz/log unit; P