• Completed

    Stereoscopic motion-in-depth perception: fMRI and neurophysiological studies

    This project is designed to advance the integration of high field fMRI in alert macaque monkeys with "informed" neurophysiology, and to apply it in addressing a long-standing research question regarding the neural processing of stereoscopic 3-D motion.

  • Completed

    Advanced Spatiomotor Rehabilitation in Blindness and Visual Impairment

    We propose a multidisciplinary approach to effective spatiomotor rehabilitation in blindness and visual impairment. For those who have lost vision, the eye-hand coordination normally available for the manipulation of objects for everyday activities is unavailable and has to be replaced by information from other senses

  • Completed
    One person looking directly at another person and picking up a cup by the handle, illustrating peripheral stereopsis

    Upper Depth Limit Across Visual Field

    Stereopsis is important for tasks of daily living such as eye-hand coordination. It is best in central vision but is also mediated by the periphery. Previously we have shown that individuals with central-field loss who have residual stereopsis in the periphery perform better at an eye-hand-coordination task. Here we sought to determine what sets the limit of stereopsis, defined as the largest disparity that supports the sustained appearance of depth, in the near periphery in healthy individuals. We used a rigorous method to determine the uppermost limit of disparity. The disparity limit is the point at which the threshold for judging dichoptic separation between the half-images is equal to the monocular width-discrimination threshold. The disparity limit at 10° was a factor of 2–4 times larger than the fovea, regardless of the meridian tested. The increase in the disparity limit with eccentricity was shallow, similar to that of Panum's area. Within this disparity limit, disparity increment thresholds were comparable for foveal and peripheral targets, illustrating the significance and utility of peripheral stereopsis, especially in the absence of foveal stereopsis.

  • Completed

    The Smith-Kettlewell Haptics Symposium

    Date: Thursday, March 29, 2018

  • Completed
    Graphic of lines of braille with finger trace trajectory superimposed over braille

    Regressions in Braille Reading

    This project explores regressions (movements to re-read text) in braille reading.

    The image on the right plots the braille reading finger movements in blue and regressions in black.

  • Completed

    Calibration of Eccentric Power Refractor

    Eccentric power refractors need to be calibrated for accommodation and gaze position for individual participants. Calibration however can be time consuming. We look at different conditions in which calibration is necessary or preferable. 


  • Completed

    The Window of Spatial Attention in Reading

    We investigate the dynamics of spatial attention while the eyes move around to gather information.

  • Completed

    Parafoveal Crowding

    Crowding increases with eccentricity, and is most readily observed in the periphery. During natural, active vision however, central vision plays an important role. Measures of critical distance to estimate crowding are difficult in central vision, as these distances are small.

  • Completed
    Hands with pen on street map closeup

    Audio/Tactile BART Station Maps

    This collaborative project between Smith-Kettlewell and the San Francisco LightHouse applies Smartpen-Based audio/tactile graphics tools to improve orientation and wayfinding by travelers with visual disabilities in and around unfamiliar transit stations.

  • Completed

    Tutorials and Reference

    These are tutorials and reference materials I have written on various topics in probability and geometry over the years.

  • Completed
    Mapped scotoma and PRL


    Walker et al (Renninger, Psomadakis, Dang & Fletcher, 2008) suggested a novel method to estimate the monocular scotoma area from perimetry data in macular degeneration based on (i) an optic-disc based estimation of the location of the fovea and (ii) the increase in the receptive field size with eccentricity. Here, Dr Walker and I introduce a new GUI that applies this method to data from the Optos OCT/SLO. With OCT, it is sometimes possible to locate the foveal pit, giving a better estimation of the fovea. The GUI takes the perimetry, fixation stability and OCT image of each eye as input. It outputs the scotoma area and map relative to the PRL and the estimated fovea. This helps clinicians and researcher to have an objective measure of monocular scotoma and its geometric relation to the PRL and the estimated fovea. The GUI computes BCEA of the PRL and reports the fovea-PRL distance which is valuable information for PRL training. A prediction of the binocular scotoma map/area is computed, assuming that the foveae in the two eyes are aligned. This map informs the user of potential benefits of binocular vision. The GUI has been used by different labs, including ours, at the Smith-Kettlewell Eye Research institute. The GUI is available to the public. A user guide is provided.