BSc in Electrical Engineering, Sharif University of Technology, Tehran, Iran
I am a cognitive psychologists and a vision scientist. I am interested in understanding reading problems in order to improve the reading experience. Along with Dr. Chandna, I study higher visual function deficits in children with cerebral visual impairment (CVI). Specifically, in collaboration with with Dr. Chandna I lead the research to investigate how CVI affects reading in each child in order to improve or develop individualized (re)habilitation techniques or assistive technologies. In addition, I am interested to understand how TBI (which is a form of CVI) affects reading in adults. I am also interested in binocular vision (stereopsis, fusion, suppression) and how the two eyes work together during daily living tasks in individuals with normal or abnormal vision, such as strabismus or amblyopia. To do so, I use (i) qualitative methods such as as in-depth interviews, surveys and questionnaires and (ii) quantitative methods such as regression, factor analysis and cluster analysis on objective data (e.g., eye-movements and accommodation measurements; behavioural data on psychophysics experiments or EEG). Furthermore, I develop applications that can be used for research or rehabilitation.
We are a Smith-Kettlewell Eye Research Institute sponsored, Blind Babies Foundation supported research advocacy group consisting of SKI researchers, select clinicians, teachers of the visually impaired, and parents of children with cerebral visual impairment.
Macular degeneration affects the central retina, often causing asymmetrical damage to the two eyes. How does this asymmetrical loss affect stereopsis — the percept of depth generated by the small separation of image features in the two eyes?
The purpose of this research study is to learn about how amblyopia, strabismus, and cerebral visual impairment affect the visual system and develop new techniques for assessing visual function in these populations.
People with mTBI often complain about dificulty in reading in spite of normal results in usual eye exams. We investigate this issue by looking at accommodation and reading rate and subjective measurement of reading difficuties for a variaty of reading tasks in normal and mTBI population. ...
In this project we try to gain a better understanding of what visual strategies people use to gather information in the world.
There is continuing debate as to whether smooth pursuit relies on the foveation of a moving target, especially when the target is compact. Previous studies have shown that gaze is placed on the center-of-mass of a target during saccadic eye movements. This research aims to understand whether eye...
Strabismus misaligned eyes is a common developmental condition in young children that can lead to amblyopia or poor vision and other forms of low vision. This project looks at the eye movements in relation to accommodation or focusing power in these patients to determine predictors of strabismus and outcome of treatment, with the goal of improving early detection, intervention and treatment.
Eye-hand coordination in AMD
In this project, we aim to understand (i) how CVI affects reading, (ii) how current rehabilitation techniques or assistive technologies help improve reading in CVI and (iii) what more can be done to assist those individuals with CVI
We investigate the dynamics of spatial attention while the eyes move around to gather information.
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.
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. Any overlap of...
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.
Aim 2 of Reaching with Central Field Loss
Active visual search
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.
This project is now completed. Please see the...
Attention and Segmentation