Eye Movement Rehabilitation in Low Vision Patients

Approximately 217 million people worldwide currently suffer from low vision, defined as mild to severe visual impairment with visual acuity between 0.5 and 1.3 logMAR2. The prevalence of low vision increases with age and may affect 7.6 million Americans by 20503. People with low vision experience significant problems across a broad range of activities of daily living, elevated levels of depression and increased mortality. The aim of the proposed project is to help people with low vision to lead more independent lives through the development of improved rehabilitation methods. To achieve this goal, this proposal brings together scientists and clinicians from Northeastern University, New England College of Optometry and the Lighthouse Guild.

In many cases, low vision causes central vision loss (CVL), forcing the patient use low resolution eccentric retina for visually-guided behavior. People with CVL can learn to attend to a specific area of eccentric retina which acts as substitute for the diseased fovea known as a Preferred Retinal Locus (PRL). Increased variability in fixation patterns and eye movements with a PRL is associated with a broad range of functional deficits. There are currently no standardized methods to select, quantify or train binocular attention and eye movement control with a PRL. Therefore, this proposal aims to develop and evaluate evidence-based methods to improve oculomotor control and visual function for people who use a PRL for visually-guided behavior.

In preliminary studies, the investigators show that real-time visual feedback helps people with CVL to improve oculomotor control with a PRL. Feedback consists of an eye tracker-controlled gaze-contingent ring centered on the retinal location of a binocular PRL, while the observer moves their eyes to keep this ring centered on a computer-controlled target. In this proposal, the investigators extend these rehabilitation methods to help patients with CVL to select and use a PRL for static and moving targets. The investigators include methods that improve awareness of the boundary of a pathological scotoma and methods that leverage the known coupling between eye and hand coordination. The use of a PRL will be assessed with eye movement and psychophysical metrics. Oculomotor control will be assessed for fixation, smooth pursuit and saccadic eye movements; and visual function will be quantified with visual acuity, contrast sensitivity, reading performance and questionnaires in the following Specific Aims:

Aim 1) Eccentric Fixation The investigators propose to examine the use of real-time visual feedback for control of a PRL for fixation. The investigators examine how PRL training is retained over time and transfers to other untrained locations, which may be required to perform different tasks, or following disease progression. The investigators will examine the relationship between PRL location, fixation stability and visual function.

Aim 2) Smooth Pursuit Eye Movements Objects in the real world and on television move around and may require smooth pursuit eye movements for sustained viewing over time. The investigators propose to use real-time visual feedback to examine how smooth pursuit with a PRL can benefit from training and how visual function varies with smooth pursuit accuracy and precision.

Aim 3) Saccadic Eye Movements Normally-sighted observers move their eyes 2-3 times per second to bring items of interest onto the fovea for high resolution inspection. These saccadic eye movements must be remapped from the diseased fovea to the PRL for people with CVL. The investigators will use real-time visual feedback to examine how saccadic eye movements with a PRL can benefit from training and how visual function varies with saccade accuracy and precision.

Aim 4) Scotoma Boundary Awareness Owing to perceptual filling in, many people with CVL are not aware of the locations or boundaries of their blind spots, which can impede the selection of and reference to a PRL. The investigators propose to provide real-time visual cues to facilitate awareness of the boundary of binocular pathological scotomas and combine this information with feedback to improve PRL training and visual function with a PRL.

Aim 5) Hand-Eye Coordination There is a close sensory and motor coupling between the visual system and hand movement system. This linkage has been associated with perceptual improvements and increases in the accuracy of oculomotor control around the locations of the hands. The investigators propose to leverage this sensorimotor integration to study PRL training and use with meta-guidance. The investigators will quantify whether PRL control and visual function can be facilitated by meta-guidance with the observer's own hands.

Overall Aims The overall goal of this minimally invasive proposal is to provide evidence-based methods to help people with low vision to maximize their residual visual function and to help them to live more independently, thereby improving quality of life and minimizing the economic, health and social burdens of visual impairment.