Abstract
Purpose: :
To study the effect of retinal defocus, and ocular dominance, on simple eye-hand reaction time in visually-normal (VN) adult individuals.
Methods: :
Sixteen VN, young-adult subjects participated in a simple eye-hand reaction time test. Different amounts of spherical (plano to +10.00D, 8 levels) and astigmatic (+0.50 D to +2.00D cylinder X90 and X180, 8 levels) retinal defocus were introduced binocularly in the spectacle plane placed over their distance prescription. Reaction time was assessed with binocular viewing using the RT-2S Simple Reaction Time Tester (Advanced Therapy Products) at a distance of 1 meter. Test target color and size simulated a conventional red-green traffic signal as would be viewed at 120 feet when driving. In addition, the effect of ocular dominance was assessed (slighting eye dominance test); different amounts and types of retinal defocus (plano, +4.00D, +10.00D spherical; +2.00D cylinder X90 and X180 astigmatic) were introduced before each eye with monocular viewing on a subset of eight of the same subjects.
Results: :
There was no significant effect (p>0.05) of either binocular spherical or astigmatic retinal defocus, or ocular dominance, on the group mean simple eye-hand reaction time. Group mean binocular eye-hand reaction time for spherical and astigmatic retinal defocus ranged from 275 to 282 ms, and from 277 to 286 ms, respectively. The group mean eye-hand reaction time across all conditions for males (n = 6) was 255 ms and 291 ms for females (n = 10), with this being a significant subgroup difference (p<0.05). Regarding eye dominance across lens conditions, reaction time was 282 ms in the dominant eye and 278 ms in the non-dominant eye, a non-significant difference.
Conclusions: :
Simple eye-hand reaction time was robust to a wide range and types of retinal defocus, thus suggesting central neural insensitivity to blur for this simple performance task. The effect might be greater for more complex tasks (e.g., choice reaction time) or in a dynamic test environment (e.g., simulated driving). The gender effect may be related to differences in overall amount and type of visuomotor experience.
Keywords: adaptation: blur • refraction • vision and action