We have already discussed active treatment options for amblyopia in general in one of our previous blogs and we will now go into further details on binocular vision training with dichoptic training.
Binocular dichoptic training is a type of vision training in which different stimuli are presented to each eye. Ideally, lower contrast stimuli are presented to the healthy eye and higher contrast stimuli to the amblyopic eye in order to compensate for decreased visual function in amblyopic eye. Having one successfully completed the required task, the contrast offset is then slowly reduced until the contrast of images presented to the healthy eye equals to those presented to the amblyopic eye. In reality though, an ideal contrast offset is sometimes very hard to determine, especially in younger children. Thus, many vision training systems do not bother with the contrast offset and present different images to each eye, without the contrast offset. Vision training tasks must be designed the way that it is impossible to complete them correctly if one is only using one of their eyes. Hence the suppression in the visual cortex of the amblyopic eye is slowly reduced and binocularity is restored. Indeed, it is believed that reduction of suppression in the amblyopic eye achieved by dichoptic training yields better results than the forced used of amblyopic eye (i.e. patching). Admittedly, there are not many studies that undoubtedly prove that dichoptic training is more effective that patching as the first step of amblyopia treatment. In fact, none of the studies have yet shown that dichoptic training is superior to patching in restoring visual acuity of the amblyopic eye. What the studies have shown, though, is that binocular vision dichoptic training is more effective in restoring binocular function than patching.
Most important binocular training studies
In this paragraph, we shall describe the most important randomized, controlled studies that dealt with the efficiency of binocular vision training. Holmes and co-workers reported in 2018 that whilst improvement is achieved faster with the addition of binocular training to continued spectacle correction, there were no significant differences at the end of the study compared to continued spectacle correction alone. In the study by Manh and co-workers from 2018, they argued that binocular training is not superior to patching, although low compliance in binocular vision training group makes those results questionable. Similarly, the compliance to binocular training was a great issue also in a study by Holmes and co-workers from 2016. Thus, we must all aim to make vision training exercises as interesting as possible for the kids. Another interesting report was published by Kelly and co-workers in 2016. Their results clearly show that visual acuity improvements are achieved faster with binocular vision training than with patching if the final outcome is somewhat similar. They also recommend binocular training as an additional option for treating amblyopia, combined with patching.
What those studies prove is the fact that no binocular training alone is superior to correct refractive correction and patching, which is no surprise. What those studies also prove, though, is the fact that improvement can be achieved faster and more if we add binocular vision training to standard treatment options such as correct refractive correction and patching. A randomized controlled study that directly compares the improvements in ‘patching plus binocular training’ group versus ‘patching alone’ group is needed perhaps more than ever in order to establish standardized protocols for binocular training.
Holmes JM, Manny RE, Lazar EL, Birch EE, Kelly KR, Summers AI et al (2018) A randomized trial of binocular Dig Rush game treatment for amblyopia in children aged 7 to 12 years of age. Ophthalmology S0161-6420:32304–32302
Manh VM, Holmes JM, Lazar EL, Kraker RT, Wallace DK, Kulp MT et al (2018) A randomized trial of a binocular iPad game versus part-time patching in children aged 13 to 16 years with amblyopia. Am J Ophthalmol 186:104–115
Kelly KR, Jost RM, Dao L, Beauchamp CL, Leffler JN, Birch EE (2016) Binocular iPad game vs patching for treatment of amblyopia in children: a randomized clinical trial. JAMA Ophthalmol 134:1402–1408
Holmes JM, Manh VM, Lazar EL, Beck RW, Birch EE, Kraker RT, Crouch ER, Erzurum SA, Khuddus N et al (2016) Effect of a binocular iPad game vs part-time patching in children aged 5 to 12 years with amblyopia: a randomized clinical trial. JAMA Ophthalmol 134:1391–1400