The Effect of Biofeedback Training on Accommodation During MFCL Wear in Young Adults

Abstract

"Purpose: Myopia currently affects 22.9% of the global population and it is estimated that 50% of the world population will be myopia by 2050. Multifocal contact lenses (MFCLs) are effective in reducing myopia progression, but with variable efficacies. One potential reason could be reduced accommodation through the MFCLs. This is due to the near add in the MFCLs superimposing peripheral myopic defocus or reducing peripheral hyperopic defocus, which then leads to a relaxation of accommodation. The drawback, however, is that if myopes reduce accommodation when reading through the MFCLs, it may reduce peripheral myopic defocus and ultimately, reduce the treatment effect of MFCLs. Recent studies show that auditory biofeedback training can help improve accommodation through the MFCLs in young myopes both immediately after the training and one week later, which may ultimately improve the efficacy of MFCLs. In this study, we evaluated, in young adults, the time course of biofeedback training in increasing accommodative response during MFCL wear and if weekly repetition of the biofeedback training and increased training duration could lead to longer lasting results. Methods: This was a prospective study with 4 weekly visits. Twenty-seven young myopes with normal accommodation and binocularity were fit with Biofinity single vision (SV) and MF (+2.00 Add center distance) CLs over both eyes and randomized to 3 groups: (1) Group 1 – single training, (2) Group 2 – regular repeated training, and (3) Group 3 – extended repeated training. During Visit 1 for all 3 groups, accommodation was measured first through the SVCLs, then through the MFCLs before and after an auditory biofeedback training at four different dioptric distances: 2.5D, 3D, and 4D. During Visits 2 and 3 for group 1, accommodation through the MFCLs was measured without the biofeedback training. During Visits 2 and 3 for group 2, accommodation was measured before and after auditory biofeedback training. During Visits 2 and 3 for group 3, accommodation was measured before and after an extended auditory biofeedback training (twice the duration). Visit 4 for all groups consisted of measuring accommodation through the MFCLs without auditory biofeedback training. Results: Analysis of the data confirmed that accommodative responses were reduced in MFCLs compared to SVCLs. One session of auditory biofeedback training was also shown to increase the accommodative responses in MFCLs at the 2.5 D, 3 D, and 4D distances and the effect of the training lasted for at least one week as supported from the data pooled together of all subjects. In subjects who received the training in the first session, effects of the training lasted for the entire month. However, increasing the number of trainings (as performed for Group 2 subjects) or the duration of the training (as performed for Group 3 subjects) did not significantly further increase the efficacy of the biofeedback training. Conclusion: Biofeedback training could potentially be used as an adjunct treatment for slowing down myopia progression when coupled with MFCL wear. Since one training of auditory biofeedback training showed success in increasing accommodative responses, it may be worthwhile to determine what changes can be made in the execution of the training to yield the best results. While this study was performed on young adults, future directions may include performing a similar study design on myopic children due to the greater accommodative capabilities of children in comparison to adults. "