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The Ipod Binocular Homebased Treatment for Amblyopia in Adults

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The Ipod Binocular Homebased Treatment for Amblyopia in Adults CLINICAL AND EXPERIMENTAL OPTOMETRY RESEARCH PAPER The iPod binocular home-based treatment for amblyopia in adults: efficacy and compliance Clin Exp Optom 2014; 97: 389–398 DOI:10.1111/cxo.12192 Robert F Hess* DSc Background: Occlusion therapy for amblyopia is predicated on the idea that amblyopia is Raiju Jacob Babu† OD primarily a disorder of monocular vision; however, there is growing evidence that patients Simon Clavagnier* PhD with amblyopia have a structurally intact binocular visual system that is rendered functionally Joanna Black§ OD monocular due to suppression. Furthermore, we have found that a dichoptic treatment William Bobier† PhD intervention designed to directly target suppression can result in clinically significant Benjamin Thompson§ PhD improvement in both binocular and monocular visual function in adult patients with * McGill Vision Research, Department of amblyopia. The fact that monocular improvement occurs in the absence of any fellow eye Ophthalmology, McGill University, Montreal, occlusion suggests that amblyopia is, in part, due to chronic suppression. Previously the Quebec, Canada treatment has been administered as a psychophysical task and more recently as a video game † Department of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada that can be played on video goggles or an iPod device equipped with a lenticular screen. and § Department of Optometry and Vision Science, The aim of this case-series study of 14 amblyopes (six strabismics, six anisometropes and two University of Auckland, Auckland, New Zealand mixed) ages 13 to 50 years was to investigate: 1. whether the portable video game treatment is suitable for at-home use and 2. whether an anaglyphic version of the iPod-based video game, which is more convenient for at-home use, has comparable effects to the lenticular version. Methods: The dichoptic video game treatment was conducted at home and visual functions assessed before and after treatment. Results: We found that at-home use for 10 to 30 hours restored simultaneous binocular perception in 13 of 14 cases along with significant improvements in acuity (0.11 ± 0.08 logMAR) and stereopsis (0.6 ± 0.5 log units). Furthermore, the anaglyph and lenticular platforms were equally effective. In addition, the iPod devices were able to record a complete Submitted: 5 April 2014 and accurate picture of treatment compliance. Revised: 17 May 2014 Conclusion: The home-based dichoptic iPod approach represents a viable treatment for Accepted for publication: 3 June 2014 adults with amblyopia. Key words: amblyopia, children’s vision, visual acuity Amblyopia traditionally has been thought of eye has been improved. In fact, more often vision by strengthening fusion and reducing as a monocular disorder that has a binocular than not, once the patch is removed after suppression, results in improved vision in consequence. According to this view, the therapy has ended, the amblyopic eye is sup- the amblyopic eye as well as a recovery of amblyopic visual system is, in some way, ‘lazy’ pressed by the fellow sighted eye and can, binocular function and stereopsis.10–12 This or immature and the logical treatment over time, lose some of the gains achieved as treatment was based on psychophysical approach is to force use of the amblyopic eye a result of the therapy.4 measurements, which demonstrated that by occluding the fellow sighted eye with a There is now evidence to suggest that the patients with amblyopia exhibited binocular patch. Previously, the patch was worn all day traditional view of amblyogenesis may be visual function if the image shown to the for months or in some cases years.1 Now incorrect. Amblyopia may be the conse- amblyopic eye had a higher contrast than we know that less patching, even as little as quence of a primary disruption to binocular that shown to the fellow eye.13 The treat- two hours per day, can be just as effective vision, in which suppression plays a major ment incorporates a task that requires infor- as all-day patching and can significantly part. This idea is not new,5 it is supported by mation to be combined between the two improve visual acuity in the amblyopic eye;2 the direct relationship between suppression eyes and begins with a patient-specific however, not all patients respond to patch- and amblyopia that has been reported in interocular contrast offset that overcomes ing and of those who do, many have residual animal models,6 by the restoration of vision suppression and allows for the task to be amblyopia after treatment is terminated in deprived animals7 as well as clinical studies completed. Over time, binocular function regardless of compliance.3 More impor- on adults8 and children9 with amblyopia. improves and the contrast offset between the tantly, binocular vision is not automatically Furthermore, it has been shown recently two eyes can be reduced until, in many cases, restored once the vision in the amblyopic that therapy aimed at promoting binocular no contrast offset is required. Using this © 2014 The Authors Clinical and Experimental Optometry 97.5 September 2014 Clinical and Experimental Optometry © 2014 Optometrists Association Australia 389 iPod binocular treatment for amblyopia in adults Hess, Babu, Clavagnier, Black, Bobier and Thompson approach, it has been demonstrated recently glasses have to be worn. We hoped that this recorded as log threshold. If stereopsis was that, as well as playing a key role in the approach may be better suited to younger unmeasurable, a log threshold of four was development of amblyopia, suppression may patients. We set out to answer two questions. recorded. also actively prevent recovery of visual func- 1. Is the home-based binocular treatment as tion by inhibiting visual cortex plasticity.14 effective as its clinic-based counterpart18 Strabismus Although this binocular treatment was ini- that was conducted under supervision? Unilateral and alternate cover tests were tially developed in the laboratory using cum- 2. Is the anaglyphic version as effective as used to determine the presence of a tropia bersome psychophysical equipment, it has the lenticular version? (manifest deviation) or phoria (latent devia- been translated recently to a more conveni- tion) and the observed deviation, if any, 14–17 ent head-mounted display and a hand- was neutralised by the use of a prism of the 12,18 METHODS held iPod device. These stimulus display required magnitude (prism cover test). platforms can be used in a clinical setting Concurrent pilot field tests were run at These were worn only during the treatment. and have the potential to be used in the the Department of Ophthalmology McGill Amblyopic participants were classified as home. We have also developed a video game University, School of Optometry and Vision exotropes or esotropes based on the direc- version of the treatment to make it as enjoy- Science at University of Waterloo and the tion of the deviation. able as possible with the goal of improving Department of Optometry and Vision compliance and hence treatment outcomes. Science, University of Auckland in New The combination of the iPod platform and Worth four dot test Zealand. The research was carried out The test was performed at both distance the video game version of the treatment is following clearance from the Institutional particularly suitable for use at home. This (1.6 m) and near (33 cm). The distance Review boards of each university and measurement was such that the lights sub- would meet with the expectations of clini- adhered to the tenets of the Declaration of cians and patients, who are used to amblyo- tended one degree of visual angle and the Helsinki. near measurement was such that a six degree pia treatment being administered in the Participants (n = 14; aged 13 to 50 years) home rather than the clinic. visual angle was subtended. The placement who had amblyopia due to anisometropia of the red-green filters was according to The use of our binocular treatment (difference in refractive error between the outside of the clinic setting poses a number convention: red filter over the right eye and two eyes), strabismus (misalignment of the green filter over the left eye. The partici- of challenges. These include compliance, eyes) or both were recruited at the indi- automatic updating of the interocular pants were to report whether they saw all the vidual testing facilities. The amblyopic par- four lights and report the colour of each. If contrast difference as binocular function ticipants had a difference of at least two lines improves and accurate dichoptic presenta- the participants reported either only two between the eyes on a logMAR visual acuity reds or three green coloured lights, they tion of visual stimuli. In the clinic, compli- chart and had impaired stereo acuity ance problems do not occur as patients were considered to have complete suppres- (greater than 40 arc seconds). sion. If they reported a total of five coloured are monitored and interocular contrast can All the participants underwent a standard be adjusted manually, based on session by light, they were considered to have diplopia clinical protocol in all the three pilot testing and if they reported four lights with the session evaluation of task performance. In sites. The clinical examination is detailed addition, dichoptic presentation can be bottom light appearing either red or green below and clinical details provided in then they were considered to have partial achieved on the iPod device using a lenticu- Table 1. lar overlay screen. The advantage of using a suppression. lenticular overlay is that the luminance con- trast is preserved. The disadvantage is that Visual acuity Bagolini striated lens test the device must be precisely aligned with the Visual acuity was obtained using a comput- Suppression by the participants was also eyes to reduce crosstalk between the images erised version of the Bailey–Lovie logMAR assessed qualitatively using the Bagolini stri- presented to each eye.
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