SPECTRAL BANDWIDTH AND OCULAR ACCOMMODATION

Previous studies have suggested that targets illuminated by monochroma tic (narrow-band) light are less effective in stimulating the eye to c hange its focus than are black-white (broadband) targets. The present study investigates the influence of target spectral bandwidth on the d ynamic accommodation response in eight subjects. The fixation target w as a 3.5-cycle/deg square-wave grating illuminated by midspectral ligh t of various bandwidths [10, 40, and 80 nm and white (CIE Illuminant B )]. The target was moved sinusoidally toward and away from the eye, an d accommodation responses were recorded and Fourier analyzed. Accommod ative gain increases, and phase lag decreases, with increasing spectra l bandwidth. Thus the eye focuses more accurately on targets of wider spectral bandwidth. The visual system appears to have the ability to a nalyze polychromatic blur to determine the state of focus of the eye f or the purpose of guiding the accommodation response.