Abstract
Purpose:
Literature suggests that multifocal lenses are associated with a decreased performance for a variety of tasks including negotiating steps, obstacles, driving and reading at certain distances, when compared to single vision lenses. In daily life we regularly perform other motor tasks, such as reaching and grasping an object. Currently, there is no evidence based data on how multifocal lenses affect the performance of such fine motor tasks when compared to single vision lenses.
Methods:
12 presbyopic subjects who were habitual multifocal spectacle wearers took part in the study. Performance was compared for multifocal lenses and single vision lenses which were prescribed following a comprehensive vision assessment and an analysis of the distances at which the tasks were carried out. Subjects had a minimum visual acuity of 0.00 LogMAR. Participants completed 3 different fine motor tasks wearing both types of correction; object width estimation, reach-and-grasp and transport-and-placement. Hand and head movements were captured by a 3-D motion capture system.
Results:
Data were analysed using ANOVA. Peak grip aperture was significantly larger when grasping the large compared to small object (p < .001). Participants also showed greater error when positioning the large compared to small object (p < .001). For the reach-and-grasp task: onset time, overall movement time, peak velocity, peak grip aperture, deceleration time and velocity corrections were not significantly affected by spectacle type (p>0.05). Interestingly, head flexion was also not affected by the spectacle type (p > .05). For the object width estimation task: no significant difference was obtained in the perceived aperture width between the spectacle types. For transport-and-placement: movement time, peak velocity, deceleration time, velocity corrections, head rotation and error in object placement were unaffected by spectacle type (p > .05).
Conclusions:
The type of spectacle lens did not affect the fine motor tasks which encompassed a range of visual angles that would lie outside the multifocal lenses’ intermediate corridor. Data demonstrates that habitual multifocal spectacle wearers can carry out fine motor tasks such as reaching and grasping just as competently as they can with single-vision lenses.
Keywords: 653 presbyopia •
408 adaptation: motion