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Dichoptic Treatment of Amblyopia in a Clinical Setting – a Retrospective Study Giovanni M CE Credit Article Dichoptic Treatment of Amblyopia in a Clinical Setting – a Retrospective Study Giovanni M. Travi, MD; Seyedbehrad Dehnadi; Behzad Mansouri, MD, PhD, FRCSC Abstract effective in improving VA and SA, and reducing suppression Purpose: Dichoptic visual stimulation has been evolving as in amblyopia. We emphasize the importance of an active a promising treatment for amblyopia. We aimed to assess follow-up regarding game monitoring and frequent patient’s the visual outcomes of Dichoptic Amblyopia Treatment reassessments. (DAT) in a clinical setting for patients who had completed all conventional amblyopia treatments and did not have any Keywords: Amblyopia, Binocular Vision, Brain Stimulation, other clinical treatment options. The primary outcome was the Visual Acuity, Visual Development improvement of visual acuity (VA) in children and adults. The secondary outcomes were improvement in stereo acuity (SA) Introduction and reduction of suppression. Amblyopia is an abnormal development of the visual system secondary to its inadequate (i.e. anisometropia and deprivation Methods: We performed a retrospective chart review of amblyopia) or erroneous (i.e. strabismic amblyopia) binocular amblyopic patients who received DAT from 2014 to 2016 stimulation during early visual development. It is usually in an eye care practice. DAT consisted of playing “Falling unilateral, and it occurs due to a mismatch of information Cubes” game on an iPod, using dichoptic presentation. between the two eyes. Beyond affecting the visual acuity, amblyopia affects contrast sensitivity,1 spatial integration,2 Results: 23 patients with a median age of 12 years-old global motion perception3–5 and depth perception.6 Moreover, (Interquartile range (IQR) = 9-30) met the inclusion criteria. it may impact negatively the quality of life, either due to 3 patients were excluded on the final VA analysis due to the low vision in the amblyopic eye, weak depth perception non-completion of treatment. The median for pre- and post- or because of the social burden of the most widely used treatment VA was 0.54 (IQR=0.41-0.84) and 0.19 (IQR=0.09- treatment, i.e. occlusion therapy.7–12 0.28) logMAR, respectively. Mean improvement in VA was 0.33 ± 0.18 logMAR (IQR=0.25-0.41) (p<0.001). Patients Recently, the understanding of unilateral amblyopia showed an improvement in SA (p=0.002) and a decrease in physiopathology has evolved and the concept that the visual suppression (p=0.003). Age group, presence of SA at baseline, loss is related uniquely to an abnormally developed visual previous treatment, amblyopia type and severity did not system has given place to the one based on an anomalous correlate with VA improvement. There was no adverse effect binocular interaction. In 2008, Baker et al.13 provided evidence such as double vision or VA reduction in the sound eye. of latent binocular function in amblyopia by balancing the visual inputs contrast between the two eyes in amblyopic Conclusion: To the best of our knowledge we showed for patients. Under experimental conditions, he showed there is the first time that DAT is a plausible amblyopia treatment at minimal suppression of the amblyopic eye and it is possible a clinical environment. The results demonstrate that DAT is to demonstrate normal binocular summation.13 Mansouri et al. evinced intact binocular interactions for supra-threshold tasks when the performance of the two eyes is matched.14 This evidence and the realization that the degree of suppression was associated with a greater difference in interocular G.M. Travi MD – Ophthalmologist, Biomedical Engineering, acuity15 led to the development of a novel binocular approach University of Manitoba to amblyopia treatment. It was based on two new pieces of S. Dehnadi – Research Assistant, University of Manitoba B. Mansouri – Neuro-Ophthalmologist, Neurology Department, VGH Adult information: a. binocularity is still present in amblyopic Medical Clinic, University of Manitoba patients and b. prolonged suppression is the cause of their Correspondence to Giovanni M. Travi MD, 2735 Pembina Hwy, Winnipeg, poor vision. Using this concept, in 2010, Hess et al.16 reported MB R3T 2H5 visual acuity improvements in amblyopic adults following Email [email protected] prolonged strengthening of fusion under specific dichoptic The authors have no financial or proprietary interest in any material or method mentioned in this article. stimulation designed to reduce the suppression. Furthermore, This article has been peer reviewed. with prolonged training under these conditions, the degree 78 Clinical & Refractive Optometry 30.3, 2019 of suppression could be reduced over time, resulting in the logMAR (log of the minimum angle of resolution) progression, re-establishment of single binocular vision.17 Subsequently, using an electronic computerized chart (PVVAT Precision several papers have addressed the results of this line of Vision Inc.) at 9 feet distance. We chose HOTV optotypes as treatment, either in lab,16–19 as prospective interventional suggested by PEDIG protocol.25 VA was converted in logMAR home-based treatment20 or as clinical trials.21–23 We are not units.26 We assessed SA at near and suppression at distance aware, however, of any report showing the experience of this through Stereo Fly Test (Stereo Optical, Chicago, USA) and new concept of amblyopia treatment implemented in a clinical Worth-4-Dot test, respectively. We converted seconds of arc of practice. SA to a log scale in the analysis to encompass the participants who did not have a measurable SA; they were set as presenting Therefore, we aimed to assess retrospectively the visual SA of 10,000 sec of arc (log = 4).27 We recorded the Worth-4- outcomes of Dichoptic Amblyopia Treatment (DAT) in a dot test results as normal if patient’s response on the test was clinical setting for children and adults who had no indication 4 lights, partial suppression if it was 4 lights with one or two of any other type of treatment (occlusion or penalization). The lights blinking and complete suppression if it was only 2 or primary outcome was the improvement of visual acuity (VA); 3 lights.27 To compute changes in suppression, we quantified the secondary outcomes were improvement in stereo acuity it as 1 (normal), 2 (partial suppression) and 3 (complete (SA) and reduction of suppression. suppression). Methods DAT consisted of home-based playing “Falling Cubes” game This study was approved by the Ethics Review Board at on an iPod platform20 using anaglyph glasses for 1 hour University of Manitoba, Winnipeg, Canada. We performed a per day for 6 weeks (in some occasions the treatment was retrospective chart review on adults and children who were extended until 11 weeks, either because patients continued to identified by a medical record search to have received DAT in show improvement or because they skipped and postponed the clinical practice of one of the authors (BM) from January appointments). Most of the patients were assessed within of 2014 to December of 2016. 1- to 2-weeks intervals, until completion of treatment. The patients’ performances were closely monitored on each The inclusion criteria were patients treated for amblyopia with follow up visit; VA was assessed and the game contrast was DAT during the abovementioned timeframe. The exclusion adjusted according to visual improvement and the patients’ criteria were: DAT treatment length of less than 4 weeks, performances on the game.20 Decreasing game scores were bilateral amblyopia, any ophthalmologic or neurologic disease discussed with the patients and their parent (if the patient was that could potentially interfere with amblyopia and visual under 16 years-old of age) and the importance of attention on acuity. Amblyopia was defined as inter-ocular VA difference the proposed treatment was reinforced. equal or greater than 0.20 logMAR units (2 logMAR lines) or one eye with VA equal to 20/40 or less with no other ocular Statistics or brain disease. Amblyopia severity was classified as mild Due to the small number of samples, we elected to use non- (VA better than or equal to 20/40), moderate (VA worse than parametric statistical tests. VA improvement was assessed 20/40 and better than or equal to 20/100), severe (VA worse through number of lines of VA improvement, proportion of than 20/100 and better than or equal to 20/400), and very change28 and mean VA improvement using test for paired severe (VA worse than 20/400).24 According to the cause of variables (Wilcoxon Rank Sum Test). The latter was also amblyopia its type was classified as anisometropic, strabismic, used to assess improvement in SA and degree of suppression. deprivation or mixed (when two causes were present). We used Mann-Whitney test to evaluate differences in VA improvement according to patient’s age group, presence We collected the following information from the patients’ of baseline SA, amblyopia severity and type. Considering charts: amblyopia type, previous amblyopia treatment or eye the uneven age distribution in our sample, we split our surgery and use of glasses (amount of time of usage). VA was participants in two categories (cutoff point = 12 years-old) gathered on pretreatment and in all following visits; stereo to analyze if this two groups differed in VA improvement. acuity (SA), presence of strabismus (and its characteristics) Spearman coefficient test was used to evaluate correlation and suppression status were noted on pre-treatment and post- between VA improvement and length of treatment and any treatment appointments only. Adverse effects (diplopia) was correlation between initial or final SA and VA improvement recorded from the post-treatment visit. We considered the last or final VA. Data were entered in Microsoft Excel datasheet visit to the clinic subtracted from the treatment period as the (Microsoft Inc., 2015) and analyzed using Excel and Matlab total follow-up after finishing the treatment.
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