A dichoptic custom-made action video game as a treatment for adult amblyopia

Abstract

Previous studies have employed different experimental approaches to enhance visual function in adults with amblyopia including perceptual learning, videogame play, and dichoptic training. Here, we evaluated the efficacy of a novel dichoptic action videogame combining all three approaches. This experimental intervention was compared to a conventional, yet unstudied method of supervised occlusion while watching movies. Adults with unilateral amblyopia were assigned to either play the dichoptic action game (n=23; 'game' group), or to watch movies monocularly while the fellow eye was patched (n=15; 'movies' group) for a total of 40hours. Following training, visual acuity (VA) improved on average by ≈0.14logMAR (≈28%) in the game group, with improvements noted in both anisometropic and strabismic patients. This improvement is similar to that obtained following perceptual learning, video game play or dichoptic training. Surprisingly, patients with anisometropic amblyopia in the movies group showed similar improvement, revealing a greater impact of supervised occlusion in adults than typically thought. Stereoacuity, reading speed, and contrast sensitivity improved more for game group participants compared with movies group participants. Most improvements were largely retained following a 2-month no-contact period. This novel video game, which combines action gaming, perceptual learning and dichoptic presentation, results in VA improvements equivalent to those previously documented with each of these techniques alone. Our game intervention led to greater improvement than control training in a variety of visual functions, thus suggesting that this approach has promise for the treatment of adult amblyopia.

Keywords: Amblyopia; Perceptual learning; Stereopsis; Suppression; Videogames; Visual acuity.

Fig. 1

General Study Design. 119 potential participants were screened for participation in the study. 54 failed screening for various reasons (e.g. resolved amblyopia, other pathologies present). The 65 participants that qualified for in-lab visit following screening (55% of screened) were scheduled to complete the study baseline assessment battery. Seven participants were subsequently excluded from the study: four could not make the required time commitment, while the other three no longer qualified after being given a refractive adaptation period (see text). Fifty-eight (n = 58) participants completed the baseline assessments, and were allocated into one of two intervention groups: game group (n = 37) or movies group (n = 21). 23 participants from the game group and 15 from the movies group completed a total of 40 h of intervention. During the intervention, visual acuity and stereoacuity only were assessed after 13 and 26 h of intervention (‘mid assessment’). At the completion of 40 h, participants repeated the complete assessment battery (‘post-intervention’). Following an 8-week period of no-contact, participants (n = 35) repeated the complete assessment battery a third time (‘follow up’). Abbreviations: Aniso: subjects with anisometropic amblyopia (no strabismus); Strab: subjects with strabismic amblyopia (both strabismic and mixed aetiologies are included).

Fig. 2

The dichoptic custom-made Unreal Tournament video game. (A) Game group participants used a mirror stereoscope to achieve alignment and play the dichoptic game. (B) Nonius lines appearing at the beginning of a training session, to allow for alignment and fusion of the two eyes. Participants viewed this through a stereoscope, when each eye receives half a cross. Participants were asked to align the two images until they perceived a complete cross in the center. (C) A screen shot of the actual game while being played by an amblyopic participant. At the start of each training session, participants adjust the alpha level of the image seen by the non-amblyopic eye (NAE) in order to overcome suppression and to achieve fusion. The set alpha level is then used to play the game, so that the amblyopic eye (AE) image is usually brighter than the NAE image. Green and red targets (see cross hairs) are also aligned prior to game play. In addition, an adaptive Gabor discrimination task is embedded in the scene viewed by the AE (gray square in center of left image). Participants were instructed to play the action game, by shooting enemies or bots as quickly as possible. A demo of the game can be seen at: http://www.youtube.com/watch?v_71RML96XxCI.

Fig. 3

Changes in visual acuity (VA) as a function of hours of either video game play or movies watching. Color coding is used throughout the figures to represent the type of amblyopia. Red squares, strabismic (either pure strabismics or mixed etiology); blue circles, anisometropic. Solid symbols: game group; Open symbols: movies group. (A) Average VA (in logMAR units) as a function of hours of training for game (solid symbols) and movies (open symbols) groups. Error bars: one SEM (here and in all subsequent figures). (B) Post-intervention VA (y-axis) as a function of baseline VA (x-axis) for individual participants. Values below the diagonal represent improved VA at post-intervention relative to baseline. Larger colored symbols show averaged VA data for anisometropic (blue) and strabismic (red) individuals. Data from previous studies using either monocular videogame play (Li et al., 2011) or dichoptic tetris (Li et al., 2013) are shown for comparison.

Fig. 4

Changes in stereopsis as a function of hours of either video game play or movies watching. (A) Log stereoacuity improvement (Log stereoacuity Pre – Log stereoacuity Post) as a function of time in intervention (hours) for both game (solid symbols) and movies (open symbols) groups. The dotted gray line indicates no improvement. (B) Individual stereoacuity data at post-intervention as a function of baseline stereoacuity for game (solid symbols) and movies (open symbols) groups, plotted in log–log coordinates. Stereoacuity of 20–40 arcsec is within the normal stereo vision range; stereoacuity larger than 400 arcsec on the Randot circles test is considered stereo-blindness and was assigned a value of 600 arcsec. Color coding is similar to previous figures. Values below the diagonal represent improved stereoacuity. Note that not all individual data points are visible due to observations with overlapping values.

Fig. 5

Contrast Sensitivity Data. Area under the contrast sensitivity curve (AULCSF) for amblyopic eye (AE) at pre-training (y-axis) as a function of post-training and follow-up AULCSF (x-axis). (A) Game group data (solid symbols). (B) Movies group data (open symbols). Blue symbols denote data for subjects with anisometropic amblyopia at post-training (blue circles) and follow up (blue diamonds); Red symbols denote data for subjects with strabismic amblyopia at post-training (red squares) and follow-up (red diamonds). Larger symbols denote averages (±SEM). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 6

Changes in reading speed and in subjective fear of losing the good eye following training. (A) Difference reading speed from preto post-intervention (top) and from baseline to follow-up (bottom). Changes are denoted as difference in averaged reading speed, averaged across all attempted sizes. (B) Changes in sub-scale 1 (SS1) of the Amblyopia and Strabismus questionnaire (ASQE), ‘fear of losing the good eye’ at post training (top) and at follow-up (bottom). Note that larger values denote less fear of losing the good eye. On all panels, boxes denote first and third quartile data (±SEM as vertical bars), and small circles and rectangles denote individual participant data. Data is shown separately for subjects with anisometropic (blue symbols) and strabismic (red symbols) amblyopia, as well as for game (filled symbols) and movies (open symbols) groups. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)