G R Watson, R A Schuchard, E Watkins
United States Department of Veterans Affairs, Rehabilitation Research and Development, Decatur, GA, United States
Background: The objectives of the study were to develop a protocol for finding a new trained retinal locus (TRL) for persons with macular scotomas and to ascertain how reading performance for persons with the TRL compared to performance with the naturally occurring preferred retinal locus (PRL). Methods: Seven subjects with a PRL to the left of the scotoma due to age-related visual impairments or other pathologies were recruited. The retinal locus characteristics/ability scale using the SLO, the Pepper Visual Skills for Reading Test and MNRead Acuity Charts was administered. Subjects were instructed in the development of the TRL, and in the use of the TRL for reading words presented on the SLO. We used an SLO fixation target in the PRL as a tag, then another target for secondary fixation with a TRL. Verbal feedback assisted in the development of the TRL. When the subject could consistently fixate and use the TRL for eye movements, we extinguished the PRL fixation target. The TRL was subsequently used for all eye movement instruction. When the subject has had sufficient practice with the TRL in the SLO, brief verbal instruction was given for use of the TRL in reading. All assessments were re-administered using the subject's TRL. Findings: All subjects with a well-developed PRL to the left of the scotoma were able to develop a TRL below the scotoma in about 15 minutes. Subjects showed no overall differences in PRL and TRL abilities such as fixation degrees, fixation ability, saccade ability and pursuit ability. Using the TRL did, however, degraded reading ability for this group. Conclusions: This project lends credence to the theory that persons with PRLs that are maladaptive for reading can learn to develop a TRL in another location. All subjects learned this process quickly. However, the usefulness of this technique and whether subjects can adapt to the use of a TRL for functional tasks such as reading is still unknown.
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