Abstract
Purpose:
To determine the effect of center-distance and center-near multifocal soft contact lenses on the horizontal peripheral defocus profile of myopic eyes.
Methods:
The right eye of 25 myopic subjects was fitted with a Biofinity Multifocal D lens (center-distance design) and a Biofinity Multifocal N lens (center-near design) with a +2.50 D add. Subjects had a spherical equivalent contact lens correction between -1.00 D and -5.75 D. An open-field autorefractor was used to measure refractive error centrally and at ±20°, ±30°, and ±40° from the line of sight in the horizontal meridian with each lens on the eye. Measurements were made while the subject looked at distance and again at near (30 cm target). Lens order and measurement starting location were randomized. A repeated-measures ANOVA was used to determine the effect of contact lens type, retinal location, and viewing distance on central and peripheral defocus. When appropriate, adjusted post hoc t-tests were performed.
Results:
The mean (±SD) age and central spherical equivalent refractive error were 24.0±1.3 years and -3.45±1.42 D, respectively. Differences in defocus with each lens type depended on the location measured (p<0.0001), and the defocus experienced with each lens type depended on the viewing distance (p=0.0002). With distance viewing, the D lens caused a myopic shift in the far periphery (30° and 40°) compared to the N lens ranging from -0.83 D to -1.92 D (all p<0.05). With near viewing, mean foveal defocus (accommodative lag) was slightly more hyperopic with the D lens (+0.86 D) than with the N lens (+0.60 D). When looking at near, far peripheral defocus (30° and 40°) was more myopic with the D lens than the N lens (range: -0.55 D to -1.59 D; all p<0.05).
Conclusions:
As expected, the center-distance multifocal resulted in a myopic shift in the far periphery when looking at distance compared to the center-near multifocal. The center-distance lens resulted in more hyperopic foveal defocus than the center-near lens when looking at near (as previously reported by others); however, the center-distance lens had significantly less hyperopic defocus in the periphery than the center-near design. Myopic defocus is hypothesized to slow eye growth in children. Compared to the center-near lens, the center-distance design resulted in a myopic shift in more retinal locations, despite a slight increase in foveal lag at near.