Sep 192011

Given that videogames are often demonized by research (and “research”) blaming them for everything from rudeness to the epidemic of youth violence, gamers often take a great deal of cheer from research attaching positive outcomes to videogame play. One such article that recently attracted some attention was work suggesting that playing videogames could correct amblyopia (often called “lazy eye”) in adults (1). Of course, given how negative results get oversold, it’s worth asking whether these have been, too. The paper appeared in the open-access journal PLoS Biology, so let’s open it up and take a look.

The fundamental problem that the authors are out to solve is that, while amblyopia can generally be corrected if it is treated in childhood, success tends to be rarer in adults. Knowing that video games have proven useful in improving adults’ abilities to perform a wide variety of visual tasks, these researchers decided to ask whether they could help treat amblyopia.

Figure 1 shows their experimental design. First they screened and assessed a group of adults with amblyopia. Then they divided these individuals into three groups. One group (10 individuals) played a total of 40 hours of Medal of Honor: Pacific Assault with the normal eye patched. An additional 3 individuals were assigned to a group that played SimCity Societies for an equal amount of time (it is unknown whether the author’s controlled for Societies‘ well-known liberal bias), again with the normal eye patched. The final seven individuals were given twenty hours of ordinary visual challenges (watching movies, reading, etc.) with the normal eye patched (occlusion therapy or OT), in order to ensure that patching alone wasn’t causing any observed improvements. Most individuals from the last two groups, following an intermediate assessment, then went on to play 40 hours of MOH.

As the authors note, there are several limitations to this study immediately apparent. The sample size was small, individuals were not assigned to groups randomly, and both participants and researchers knew what kind of treatment they were getting. This does not mean we should disregard the results. However, they do need to be taken with a grain of salt until the findings can be replicated in a larger sample.

And there is good cause to try to replicate these findings. Figure 2 is, unfortunately, something of a symbol party (the symbols and colors identify individual subjects by their type of amblyopia), so we’re better off focusing only on panel D, at lower right. The first item in panel D is a logMAR chart, used to measure visual acuity, and it probably looks familiar to you. Each line on the chart represents 0.1 logMAR units, and as you can see, the lower the score, the better your vision. The panel to the right of that shows the averaged data from all twenty individuals after OT and videogame therapy (VG). Here they are showing the percentage improvement in acuity in crowded conditions (the whole chart) or in isolation (a single letter). OT did not produce any improvement in acuity, while 40 hours of VG therapy produced an average 30% improvement in acuity. The other two graphs here indicate that improvement in acuity was unrelated to baseline acuity, and that the crowding index (the loss of acuity due to the presence of other letters) did not change substantially due to therapy.

This is a critical figure because, as the authors state, “reduced visual acuity is the sine qua non of amblyopia.” Substantial improvements in acuity, therefore, represent a major goal of therapy. Perceptual learning, in which participants make subtle visual judgments using their amblyopic eye, has been shown to improve acuity in adult amblyopes as well. If videogames can produce a comparable improvement, however, they may prove just as efficacious because they encourage therapy (=play) through fun.

Panels A-C of Figure 2 show the raw results and percentage improvements for each individual group. Two additional points are worth noting. Panel B shows that the 20h of occlusion therapy were ineffective, but the subsequent 40h of MOH improved acuity in all continuing individuals. However, it should be noted that while the gaming took place at the research location, the occlusion therapy was done on the individual’s own time and self-reported. This study therefore does not control for the benefits of a monitored and enforced eye-exercise regimen.

Panel C is also of interest. Although the group here is small (and the data correspondingly noisy), it appears that their acuity was improved by both SimCity and MOH. This was somewhat unexpected, because in the past positive visual effects produced by action video games have not been replicated by non-action games. Understanding why that’s not the case here may help provide some additional insights into the mechanisms by which games improve acuity in these patients. I haven’t played SimCity Societies, but having played previous SimCity iterations I know that these games often require the player to integrate a variety of visual information (traffic flow, electricity, dynamic economies) simultaneously, which may underlie the observation. Had these subjects actually played videogame chess, their improvement might have been less.

The authors went on to test the subjects’ vision in various ways. Figure 3 shows a test of positional acuity, and is rather badly made, but gets the point across that positional acuity (assessed using the funky little chart in panel A) improved in the game-playing group (panel B). This included both increases in “sampling efficiency”, related to a fitted number of correct positions extracted (out of 8) (panel C and E-SB2) and decreases in “internal noise”, or the degree to which the individual’s own eyes interfere with his assessment of position (panel D and E – SA5). The results in panel E compare improvements in efficiency and internal noise, with the three labeled graphs comparing results in the non-amblyopic eye (NAE) to the amblyopic eye (AE) before and after videogame treatment.

The authors also decided to test the effect of the games on spatial attention, as they report in Figure 4, by briefly showing the subjects a field of dots (at a size where they could be easily seen), followed by a checkerboard pattern and asking them to report the number of dots seen (panel A). Not all the individuals had an appreciable difference between the non-amblyopic eye and the amblyopic eye prior to the VG treatment (panel B). However, the degree of improvement in spatial attention tended to be greater the worse the initial condition was (panel C), including for SimCity players (symbols surrounded by dotted circles). For the worst-off subjects (dotted circle in panel B), significant improvements in accuracy and response time were observed (panel D-F).

Finally, the authors tested the stereovision of some subjects using a standard test (Figure 5). Again, substantial improvements were noted in all those tested (which excluded subjects with strabismus), to the degree that some of them were effectively cured.

These results show that playing video games produced dramatic improvements in vision for adults with amblyopia by a variety of measures. However, this study had many limitations, and nobody should go around prescribing (or self-prescribing) videogames as amblyopia therapy just yet. The sample size here was very small, and because of the way groups were assigned the various populations differed in non-trivial ways (the MOH group, for instance, was younger and more male than the others). The conditions for occlusion therapy were very different from those used in the videogame therapy, which could have contributed to the different outcomes. Even if a more comprehensive trial shows similar results, more work will be necessary to identify the best course of treatment, which I note is unlikely to take the form of a 24-hour Modern Warfare 3 binge fueled by Bawls and pizza.

That said, these results appear to justify a larger, more complete study, which we can certainly hope to see in a few years from these authors.

1) Li, R., Ngo, C., Nguyen, J., & Levi, D. (2011). Video-Game Play Induces Plasticity in the Visual System of Adults with Amblyopia PLoS Biology, 9 (8) DOI: 10.1371/journal.pbio.1001135

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