Effect of multifocal spectacle lenses on accommodative errors over time: Possible implications for myopia control.

The study purpose was to improve understanding of how multifocal spectacle lenses affect accommodative errors and whether this changes over time. Fifty-two myopes aged 18 to 27 years were allocated randomly to one of two progressive addition lens (PAL) types with 1.50 D additions and different horizontal power gradients across the near-periphery boundary. Lags of accommodation were determined with a Grand Seiko WAM-5500 autorefractor and a COAS-HD aberrometer for several near distances with the distance correction and the near PAL correction. For the COAS-HD the neural sharpness (NS) metric was used. Measures were repeated at three-month intervals over 12 months. At the final visit, lags to booster addition powers of 0.25, 0.50, and 0.75 D were measured. Except at baseline, both PALs' data were combined for analysis. For the Grand Seiko autorefractor, both PALs reduced accommodative lag at baseline compared with SVLs (p < 0.05 and p < 0.01 at all distances for PAL 1 and PAL 2, respectively). For the COAS-HD, at baseline PAL 1 reduced accommodative lag at all near distances (p < 0.02), but PAL 2 only at 40 cm (p < 0.02). Lags measured with COAS-HD were greater for shorter target distances with PALs. After 12 months' wear, the PALs no longer reduced accommodative lags significantly, except at 40 cm distance, but 0.50 D and 0.75 D booster adds decreased the lags to those measured at baseline or less. In conclusion, for PALs to reduce accommodative lag effectively, addition power should be tailored to typical working distances and after the first year of wear should be boosted by at least 0.50 D to maintain efficacy.