Effect of customized near addition lenses on transient myopia induced by near-work

Li Nan¹, Kenneth Seger², Melanie Crandall², Bai-Chuan Jiang²

¹Clinical College of Ophthalmology, Tianjin Medical University, Tianjin Eye Hospital, Tianjin, China; ²College of Optometry, Nova Southeastern University, Fort Lauderdale, Florida, USA

Purpose: To verify whether optimal near add power can reduce near-work induced transient myopia (NITM).

Methods: Eighteen subjects including nine progressive myopes (PMs) and nine stable myopes (SMs) were involved in this study. We measured the accommodative error and the near phoria at 40 cm under fully corrected conditions for each subject. These findings were then used to determine optimal near-add power for each subject based on formulae derived from a previous study. Under both with and without near-add conditions, NITM was obtained by comparing the refractions immediately before and after performing continuous computer work at 40 cm for an hour. The refraction was determined by a COAS aberrometer.

Results: Using customized near-addition lenses (C-ADD) we found significantly decreased retinal defocus from 0.49 ± 0.12 (SD) D to 0.08 ± 0.11 D. The near phoria showed a significant exophoric shift from -1.84 ± 1.95 prism diopter (pd) to -5.37 ± 1.63 pd, but was still in the normal range. We also found that the differences in NITM between the two groups and between the two conditions (ie, with and without C-ADD) were both significant. Further comparisons indicated that the NITM in the SM group was significantly reduced after using C-ADD; in the PM group the reduction of NITM was not significant.

Conclusions: The results suggest that C-ADD balances the load of accommodation and vergence, significantly decreasing retinal blur during the near-work, and may be able to reduce the NITM.

Keywords: myopia, near-addition lenses, accommodation, near phoria, transient myopia