Abstract
Purpose: :
To assess objectively changes in the NITM (nearwork-induced transient myopia) parameters of initial magnitude and its decay duration, as well as accuracy of the near accommodative steady-state response and clinically-based accommodative facility, following 6 weeks of home-based monocular and binocular accommodative vision training (i.e., oculomotor learning) in asymptomatic myopes.
Methods: :
10 young-adult myopes with a mean age of 23.6 (±2.2) participated. The experimental paradigm consisted of a baseline session and two follow-up sessions at the end of the 3rd and 6th weeks of training. At the first session, baseline refractive state and the selected static and dynamic accommodative functions were assessed objectively. Measurements were repeated at the two follow-up sessions. Conventional home-based vision training emphasizing dynamic aspects using step inputs included lens flippers (±2D) at near (40cm), Hart chart at distance (6m) and near (40cm), and prism flipper (6pd) training at near (40cm), all of which were performed for 20 minutes a day 5 days a week for 6 weeks (10hrs total). Thus, both blur and vergence-driven accommodation, and their interactions, were involved.
Results: :
The dynamic accommodative response functions improved significantly with training, whereas the steady-state (static) response functions were only slightly improved. Dynamic: NITM decay duration decreased significantly with training from 101secs to 74secs. Lens flipper rate increased significantly from 11 to 16cpm in the OD, 11 to 19cpm in the OS, and 8 to 11cpm in the OU. Hart chart rate increased significantly from 22 to 33cpm in the OD. Static: Initial NITM magnitude decreased slightly from 0.53D to 0.47D, whereas the steady-state accommodative response increased slightly from 2.64D to 2.72D, following training.
Conclusions: :
Training of the accommodative system resulted primarily in improved dynamics in both the laboratory and clinical measures. The results suggest the presence of rapid motor learning involving both the parasympathetic and sympathetic systems. Faster dynamics would result in decreased time-integrated retinal defocus, a potential myopigenic factor. In addition, the results suggest improved blur processing with training.
Keywords: accomodation • myopia • refractive error development