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Plasticity of fixation in patients with central vision loss

Published online by Cambridge University Press:  11 December 2009

LUMINITA TARITA-NISTOR ,
ESTHER G. GONZÁLEZ ,
SAMUEL N. MARKOWITZ  and
MARTIN J. STEINBACH
LUMINITA TARITA-NISTOR
Affiliation:
Vision Science Research Program, Toronto Western Research Institute, Toronto, Ontario, Canada
ESTHER G. GONZÁLEZ*
Affiliation:
Vision Science Research Program, Toronto Western Research Institute, Toronto, Ontario, Canada Centre for Vision Research, York University, Toronto, Ontario, Canada Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada
SAMUEL N. MARKOWITZ
Affiliation:
Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada
MARTIN J. STEINBACH
Affiliation:
Vision Science Research Program, Toronto Western Research Institute, Toronto, Ontario, Canada Centre for Vision Research, York University, Toronto, Ontario, Canada Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada
*
*Address correspondence and reprint requests to: Esther G. González, Vision Science Research Program, Toronto Western Research Institute, 399 Bathurst Street, FP 6-212, Toronto, Ontario, Canada M5T 2S8. E-mail: gonzalez@yorku.ca
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Abstract

The aim of this study was to explore the plasticity of fixation in patients with central vision loss. Most of these patients use preferred retinal loci (PRLs) in the healthy eccentric part of the retina to fixate, but fixation stability and retinal location are not always optimal for best visual performance. This study examined whether fixation stability and a new PRL location can be trained and whether these changes in ocular motor control transfer into better reading performance. Six patients with age-related macular degeneration participated in the study. Fixation stability measurements, microperimetry, and auditory biofeedback training were performed with the MP-1 microperimeter. The auditory biofeedback was used during five 1-h long training sessions to improve fixation and relocate the PRL. Fixation location and stability were recorded while viewing four different targets: a cross, a letter, a word, and a nine-cycle radial grating. Visual acuity was assessed with the Early Treatment Diabetic Retinopathy Study (ETDRS) chart and reading performance with the MNRead test. The results showed that all patients developed a new PRL in an optimal location for reading, and they were able to use it consistently while viewing different targets. Fixation stability improved 53% after training. Learning transferred to the old PRL even though fixation stability at this location was not trained. All these improvements in ocular motor control translated into better reading performance: reading speed improved 38% and reading acuity and critical print size gained two lines. We conclude that the ability of the ocular motor system to fixate is flexible in patients with central vision loss: a new PRL can be trained, fixation stability can be improved, and learning transfers to an untrained location. These gains in ocular motor control result in better visual performance. This property can be successfully used to optimize the residual vision of patients with central vision loss.

Keywords

Central vision lossPRLFixation stability trainingPlasticity of ocular motor system
Type
Research Articles
Information
Visual Neuroscience , Volume 26 , Issue 5-6 , November 2009 , pp. 487 - 494
Copyright
Copyright © Cambridge University Press 2009

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