We simulated the effects of longitudinal (axial) chromatic aberration and defocus on contrast of the long-, middle- and short-wavelength components of the retinal image to determine whether the effects of chromatic aberration are sufficient to drive accommodation. Accommodation was monitored continuously while subjects (12) viewed a 3 c/deg white sine-wave grating (0.92 contrast) in a Badal stimulus system. The contrasts (amplitudes) of the red, green and blue components of the white grating changed independently to simulate a grating oscillating from 1 D behind the retina to 1 D in front of the retina at 0.2 Hz. Subjects responded strongly to the chromatic simulation but poorly to a luminance control. The results support the hypothesis that focus is specified by the contrast of spectral-wavebands of the retinal image, and that conventional color mechanisms, monitoring chromatic contrast at luminance borders (1-8 c/deg), mediate the signals that specify dioptric vergence.

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During Rapid Serial Visual Presentation, readers can read sans-serif type about 20% faster at very small sizes. This advantage disappears at larger sizes. The study was done with fonts specially designed to control typeface parameters other than the serifs. The results suggest that rendering serifs at small sizes may be counterproductive.

One of the main early complaints of cataract patients, even when these patients exhibit only mild glare problems as measured by standard tests, is that glare impairs their night driving. To provide a better measure of the patients' impairment, glare tests should include measurements of the glare effect in conditions more similar to those found in night driving. During night driving the ambient light is very low, and oncoming headlights present a transient temporal pattern. Furthermore, the objects of interest often appear initially in the peripheral visual field. Thus three important characteristics of glare in night driving are that the ambient illuminance is in the scotopic-mesopic range, the detection stimulus is in the periphery, and the glare source is transient. Most of the current glare testers measure glare only at photopic levels, and all the glare tests that we know of use only steady sources of glare with foveal discriminations. All these conditions are dealt with. The transient glare source raised thresholds by 0.5-0.75 log unit more than the steady glare source, and the transient glare effect was more pronounced and more long lasting in the periphery. Standard glare testers seriously underestimate disability glare effects in everyday life.

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