The present disclosure provides an improved method for photobleaching an eye of a subject. The disclosed method may be used in a number of psychophysical test methods, including, but not limited to, measurement of dark adaptation. The improved method for photo-bleaching involves at least one of the following improvements: (i) the use of a bleaching light emitting a particular wavelength of light or a tailored spectrum of wavelengths; (ii) restricting or otherwise spatially tailoring the region of the retina that is subject to photobleaching; and (iii) utilizing a bleaching light having an intensity that is at or below the intensity of ambient daylight. The present disclosure additionally provides a combination of a photobleaching light and an apparatus to administer a psychophysical test suitable for use in practicing the disclosed methods.