Visual psychophysics, which investigates responses to visual stimuli, has revealed various visual functions. Through the study of psychophysics, a new clinical test could be developed that is much more innovative than those now in clinical use. This issue of the Japanese Journal of Visual Science contains two review papers on color perception, and depth perception, and a topic paper on motion perception. We hope that these papers will be helpful to readers in imaging clinical applications of psychophysics.
The front end of the visual mechanism, which mediates color vision, is comprised of three types of cones, which have different sensitivities to light. Several invasive approaches to measuring the L/M cone ratio on the human retina have recently been proposed. This article briefly addresses two of those methods: direct measurement of the L/M ratio by analyzing images of the living human retina, and indirect estimation based on the neurophysiological method. The former was derived from an adaptive optics system, combined with a selective bleaching technique and retinal densitometry; the latter was derived from spectral sensitivity measured via electroretinogram (ERG). The sensitivity is then best fit with a weighted sum of L and M cone sensitivities of each subject, which are compensated for using genetic analysis. The L/M cone ratio varies widely among observers, ranging from 0.26 to 16. This result is supported by both of these methods.
The human visual system uses a variety of depth cues to perceive the 3D world. The use of these cues in perceiving static images has been studied, including mutual interactions between cues. Although it is believed that there are also many cues involved in perceiving motion in depth, much less is known in that regard. We summarize cues for perceiving motion in depth, focusing on two binocular cues, and describe studies that suggest different roles of the two cues.
From the microperimetry study, preferred retinal locus (PRL) evaluations, such as location and stability, and bilateral ocular examinations are important because the PRL can change easily in macular disease. The concept of pseudo-central fixation is also explained. The newly developed microperimeter enables qualitative evaluation, making it easy to compare changes in the same location under the same conditions during follow-up visits. Microperimetry is also expected to have applications in low-vision care. Examinations are conducted by tracking the fundus and overlaying the data on color photographs after the examination. Visual function evaluation is also essential, with the understanding that certain features of the instrument, such as low light level, might not facilitate direct comparison with other perimeters. The expectation is to develop an all-in-one instrument that can evaluate visual function at the same time as fundus image screening, optical coherence tomography and angiography.
Purpose: We investigated the effect on visual function of temporary miosis after blinking.
Methods: Included in this study were 17 eyes from 17 normal subjects. We used a modifi ed CAT-2000TM (Menicon, Tokyo, Japan) with an electronic pupillometer built into the contrast visual acuity measuring device. Two types of blinking, spontaneous and voluntary, were used. We evaluated pupil size before (basic size) and after blinking (minimum size). Contrast visual acuity was measured after instillation of cyclopentolate hydrochloride (Cyplegin®) using an artifi cial pupil whose diameter was measured before and after blinking.
Results: Pupil diameters exhibited signifi cant temporary miosis after blinking. Pupil variation was about 0.5 mm with spontaneous blinking and about 0.5～1.5 mm with voluntary blinking. Contrast visual acuity increased signifi cantly, about 1 or 2 lines, when artifi cial pupil size reduced more than 1.0 mm from the basic size.
Conclusions: This study suggests that temporary miosis after blinking produces an increase in depth of focus and improves retinal image quality, there by affecting visual function.
The fovea is temporally horizontally dislocated from the anatomical axis of the eye. Using ray tracing, spot diagrams at the fovea were calculated for intraocular lenses (IOLs) with horizontal decentration and/or tilt. Side-section views of the convergent rays at the Gaussian focus and fovea were also calculated. The section views were expressed in terms of energy density distribution. The calculations were performed with a spherical IOL and an aspherical IOL with no spherical aberration at the anatomical axis. It was found that the aberration at the fovea can be reduced by horizontal decentration and/or tilt. It was also shown that the depth of focus of a spherical IOL is longer than that of the above type aspherical IOL, and that in the spherical IOL the energy peak at the Gaussian focus is sharper than that at the least confusion circle.