A technique to train new oculomotor behavior in patients with central macular scotomas during reading related tasks using scanning laser ophthalmoscopy: immediate functional benefits and gains retention

Abstract

BackgroundReading with a central scotoma involves the use of preferred retinal loci (PRLs) that enable both letter resolution and global viewing of word. Spontaneously developed PRLs however often privilege spatial resolution and, as a result, visual span is commonly limited by the position of the scotoma. In this study we designed and performed the pilot trial of a training procedure aimed at modifying oculomotor behavior in subjects with central field loss. We use an additional fixation point which, when combined with the initial PRL, allows the fulfillment of both letter resolution and global viewing of words.MethodsThe training procedure comprises ten training sessions conducted with the scanning laser ophthalmoscope (SLO). Subjects have to read single letters and isolated words varying in length, by combining the use of their initial PRL with the one of an examiner's selected trained retinal locus (TRL). We enrolled five subjects to test for the feasibility of the training technique. They showed stable maculopathy and persisting major reading difficulties despite previous orthoptic rehabilitation. We evaluated ETDRS visual acuity, threshold character size for single letters and isolated words, accuracy for paragraphed text reading and reading strategies before, immediately after SLO training, and three months later.ResultsTraining the use of multiple PRLs in patients with central field loss is feasible and contributes to adapt oculomotor strategies during reading related tasks. Immediately after SLO training subjects used in combination with their initial PRL the examiner's selected TRL and other newly self-selected PRLs. Training gains were also reflected in ETDRS acuity, threshold character size for words of different lengths and in paragraphed text reading. Interestingly, subjects benefited variously from the training procedure and gains were retained differently as a function of word length.ConclusionWe designed a new procedure for training patients with central field loss using scanning laser ophthalmoscopy. Our initial results on the acquisition of newly self-selected PRLs and the development of new oculomotor behaviors suggest that the procedure aiming primarily at developing an examiner's selected TRL might have initiated a more global functional adaptation process.

A conceptual model for vision rehabilitation

“…Moreover, our maturing population, with increasing rates of sight-threatening, age-related conditions, could compound issues with visual impairment and dysfunction secondary to brain injury [71], which can affect the patient more severely on the person level or functional vision level. It has already been shown that these expanding, age-related visually compromising conditions interface with rehabilitation [72–76], and these novel concepts [58,75,77–80], as delineated previously, must account for and integrate these disorders into the framework to expand the knowledge base accordingly.…”

How effective is eccentric viewing training? A systematic literature review

“…However, the effect of training on distance VA has received some attention. An increase in distance VA was reported in two small before and after studies ( n = 5 for each study), one randomised trial, and one case study . A change in distance VA was found in another small controlled before and after study, but this failed to reach significance when Bonferroni correction was applied for multiple comparisons .…”

“…A change in distance VA was found in another small controlled before and after study, but this failed to reach significance when Bonferroni correction was applied for multiple comparisons . In the earliest of these studies, Deruaz et al . reported a significant improvement ( p = 0.022) in distance VA after EV training administered using a scanning laser ophthalmoscope, although the improvements recorded for individual participants did not exceed the test‐retest repeatability.…”

“…The purpose of SES training is to remove the need for forward saccades. Alternatively, ‘eye movement training’ programmes aim to optimise the ability of the saccadic eye movements to consistently place the image of the object of interest on the preferred retinal locus …”

Scotoma Visibility and Reading Rate with Bilateral Central Scotomas

“…The patient is still unable to perceive the location of his/her scotoma, but the examiner can coach the patient to move his/her eye to a more “optimal” location. 11,12 Use of these instruments has yet to become widely implemented in routine low vision evaluations, possibly because of their limited accessibility, high cost, increase in examination time, and the need for greater technical skill. Eccentric viewing training remains focused on helping the patient recognize where they have to look to perceive objects and perform visual tasks.…”