Dr. Arthur Bradley has been a member of the IU School of Optometry faculty since 1985. He has played an active role in teaching visual perception, binocular vision, and optics in the O.D. program. Dr. Bradley has taught extensively in the graduate program (visual optics, spatial vision, non-invasive visual assessment, visual neurophysiology), and he maintains an active psychophysics and optics research laboratory.
We tend to think that optical aberrations, and defocus simply produce image blurring. We also tend to think that image degradation is a one-dimensional process (images are either better or worse). We have been investigating the often complex perceptual consequences of optical defocus and aberrations (see publications on optics). For example, the familiar oscillating MTF seen in defocused optical systems can be visualized by comparing the contrast changes and phase shifts in the star-burst patterns below. We have recently been able to show that it is the phase shifts and not the amplitude changes that limit defocused visual acuity for hyperopes but not for myopes. Examples of a Ð1 diopter defocused letter E is shown below, the top E was imaged in front of the retina (myopia), while the bottom E was imaged behind (hyperopia/presbyopia). Notice that the phase reversals produced by the blur completely change the appearance of the hyperopic E.
In addition to examining the impact of phase shifts caused by blur, we have also
studied the image doubling effects of blur. For example, hyperopic defocus with
astigmatism and spherical aberration will create monocular diplopia as shown in
the images below. Many subjects report this diplopia.
We have also examined the role of color and wavelength on visual perception of
location and depth, and we have examined the feasibility of correcting for
aberrations to improve retinal image quality and thus vision.