A mobile application was able to accurately screen children for amblyopia in this study. Photo: Getty Images.

As part of an ongoing effort to find and develop new ways of screening for amblyopia, the leading cause of permanent vision loss in children, investigators recently looked into a new method involving the use of an iPad game. By having a cohort of schoolchildren look through polarizing filters on the digital screen and compare the brightness between graphics, clinicians in this study were able to accurately measure interocular brightness disparity, acuity and color vision, which they found was able to help effectively detect those with amblyopia.

A total of 208 children, including 121 girls and 87 boys ages three to 14, participated in the study at their school, which was provided with iPads, filters, glasses and pinholes for the testing period. The investigators explained, “To measure brightness disparity, binocular image separation is created by wearing polarizing glasses combined with complementary linear polarizing filters positioned over two vertically aligned spaceships on an iPad screen. Through this polarizing filter arrangement, the right eye views only the bottom spaceship, rivalrous with the black background viewed by the left eye, and the left eye views only the top spaceship, rivalrous with the black background viewed by the right eye,” they wrote in their paper. In addition, two spaceships are presented on the screen during the test with brightness differences ranging from 0.3 to 1.8 logMAR in increments of 0.3, and test-takers are repeatedly prompted to choose the brighter spaceship.

Of the 208 children who took the test, 204 were able to adequately complete the protocol and provide results. The investigators determined that binocular brightness balance on the iPad was able to detect amblyopes with 100% sensitivity and specificity. With the normal acuity cutoff at 20/30, amblyopia was detected in just one student for a prevalence of 1% in this cohort, while non-amblyopes were confirmed through visual acuity pinhole testing.

“The mean difference between iPad and E-Chart visual acuities with pinhole was 0.02 logMAR with limits of agreement from -0.08 to +0.11 logMAR,” the investigators wrote. “iPad and printed plates color vision testing produced identical results.”

Another positive outcome from the results: testing times were brief, lasting no longer than a couple of minutes to complete all three measurements. “Mean and range testing times for brightness sense, color vision and visual acuity were 32.7 seconds (range=12-63 seconds), 52.8 seconds (range=17-95 seconds ) and 88.75 seconds (range=41-188 seconds), respectively,” they wrote. Plus, they reported that responses from exit pleasure polls given to each participant were positive, especially for those younger than eight.

Overall, these results demonstrate that measuring interocular brightness disparity, acuity and color vision through an application on a mobile device such as an iPad can be an enjoyable and effective way to screen children as young as three years old for amblyopia. In addition, the investigators noted that this method is more accessible than others, as it offers a virtual option.

“Online vision screening and telemedicine that directly measure amblyopia rather than assess risk factors may eventually displace amblyopia as the number one cause of permanent vision loss in children,” they concluded.