training oculo-motor control to improve vision when using a preferred retinal locus

Conditions: Central Visual Impairment

Summary: when high-detail vision is lost due to a retinal disease such as macular degeneration, people see poorly, and have difficulty with eye movements (oculo-motor control). this preliminary study will investigate a potential behavioral intervention that may improve the ability to perform vision-related daily activities such as reading, recognising faces and watching television. the intervention involves many sessions that will train visual perception and eye movements over a period of a few months. participants will have either lost central vision in both eyes or have normal vision (control group).

the purpose of the study is evaluate a potential treatment for loss of (foveal) central vision in both eyes which results in the use of a preferred retinal locus (prl). the treatment is a series of 16 sessions of about one-hour duration that will involve a mixture of oculomotor control (omc) training, perceptual training, and scotoma awareness. two groups will receive the training: (1) central vision loss; and (2) normal sight who will use a simulated scotoma (called control group below). a single-site, two-way mixed factor, one within-subject and one between-subject, minimal-risk phase-2 study. each participant with vision loss or in the control group will attend for three outcome-measurement visits and 16 training visits over a period of about two months (at 2 visits per week). feasibility metrics will be obtained during recruitment and study conduct. prl and omc metrics will be obtained at every visit. outcome metrics will be obtained before treatment, following 8 training sessions, and following 16 training sessions. participants in the control group will experience a simulated central scotoma created by a gaze-contingent visual display system that simulates the loss of central vision by obscuring a region of central vision during testing and training. participants will be trained using an integrated oculo-motor and perceptual training approach using a gaze-contingent visual display to provide scotoma awareness. two tasks will alternate: (1) a textured search target that suddenly shifts, drifts smoothly, or is stable, requiring the subject to make a saccade, a smooth pursuit, or fixate, respectively, following which there is a same-different task to test attention; and (2) target following and visual search for (a) face within distractors, (b) object recognition and location, and (c) word recognition and object identification over cluttered background. during training, for the vision-loss group, the binocular scotoma (created by the retinal lesions) will be outlined using a gaze-contingent system, so that the subject will see a border at the edge of their binocular scotoma that moves with gaze, alerting them to the location of the scotoma. in addition to the 16 training sessions, there will be longer (2.5 to 3 hours) measurement sessions: (1) before training; (2) after 8 training sessions; and (3) after 16 training sessions. due to the number of procedures, the first measurement session might consist of two sessions. thus, each participant with vision loss will participate in 19 or 20 sessions in total. ideally, participants will attend for two visits per week. however, the schedule is flexible and can be adapted to a participants schedule.

Eligibility criteria:
central vision loss group inclusion criteria: * bilateral foveal loss that includes the fovea in each eye, as determined through retinal examination * fluent in english * cognitive function moca (montreal cognitive assessment) test \>20 * binocular visual acuity 20/800 or better * able to sit for at least an hour exclusion criteria: * speech impediment * history of neurological or psychiatric disease * inability to provide informed consent * inability to follow instructions in english normal vision control group inclusion criteria: * fluent in english * cognitive function moca (montreal cognitive assessment) test \>25 * binocular visual acuity 20/40 or better * able to sit for at least an hour exclusion criteria: * any ophthalmic disease that might impact on the conduct of the study, especially conditions that cause vision field loss * speech impediment * history of neurological or psychiatric disease * inability to provide informed consent * inability to follow instructions in english