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Editors Selection IGR 9-3

Comment

Comment by Chris Johnson on:

This publication reports that there were statistically significant increases in thickness in the superior temporal macular ganglion cell layer-inner plexiform layer (mGCIPL) and superior mGCIPL thickness, and an increase in mean macular sensitivity (mMS) in a small group of glaucoma patients (27 patients, 54 eyes), The glaucoma patients underwent daily viewing of stereoscopic images for 15 to 20 minutes while wearing glasses with a red filter over one eye and a blue filter over the other eye. The authors attribute these findings to neural cell plasticity that was produced by the 3 months of visual perceptual plastic training. While the primary goal of glaucoma treatment is to prevent or delay progressive changes, there has also been interest in developing methods to improve the visual performance of eyes with glaucomatous damage. The findings of this investigation suggest that certain training procedures may accomplish this goal, although the lack of important clinical patient information, inferences of causative factors responsible for this improvement based on descriptive findings, the lack of a control group, and the optimistic interpretation of results draws these conclusions into question, as indicated below.

Many of the measurements did not produce a statistically significant difference in the pre and post training period. Those that did show a statistically significant difference were rather small. Thus, while they may be statistically significant, they may not be clinically meaningful.

Although the authors had participants undergo two prior visual fields before enrolling in the study, it has been reported that improvements in visual field sensitivity can occur for up to six years (Gardiner et al., Optometry and Visual Science,2008, 85: 1043-1048). This could certainly account for the pre and post sensitivity differences, and it also indicates why a control group would have been useful to include in the present study.

There is very little information (visual field status, refractive errors, mode of treatment, etc) that is provided for the participants in this study, making it difficult to determine the underlying characteristics of the population tested.

It is not clear why the authors chose to use stereoscopic images on a vr headset as the method for enhancing performance, and why the macula was selected as the visual field location to evaluate. Much more is known about peripheral visual field impairment produced by glaucoma than for the macula, and the use of stereoscopic images also seems quite remote from what the authors were evaluating. Why would stereoscopic images be the most preferred means of improving performance in glaucomatous eyes?

Although the authors provide a possible mechanism for this improvement in performance and in the thickness of certain portions of the mGCIPL, this is mainly based on a speculative inference rather than a direct evidence-based outcome. Although this may be a possible explanation for this finding, much further work will be needed to establish this as the basis for this effect.

Although the investigators attempt to provide an objective, unbiased effort towards exploring a research problem, there is a strong incentive to report positive results rather than negative or neutral ones. In this view, it is important for other researchers to determine if they are able to replicate these findings because they do not have a direct interest in the outcome becoming successful. It will be informative to see if the results reported by these authors can also be found by other investigators who do not have a direct interest in a successful outcome of this research.

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