Abstract
Purpose :
It has been suggested that the visual system of individuals with myopia may be less dynamic. We measured eye movements in myopes and emmetropes during various indoor and outdoor activities to test the hypothesis that myopes make fewer eye movements for more visually demanding tasks.
Methods :
Eye movements (number of fixation changes) were evaluated using a portable ViewPoint EyeTracker® while subjects performed 6 indoor tasks [read on laptop, read book, play Tetris, watch TV, walk to an office, walk back to lab while using an iTouch]; and 3 outdoor tasks [walk in park, walk on busy street, walk in park while using an iTouch].
Subjects were 38 young adults (21-32yrs) with best-corrected VA 0.0 LogMAR (20/20) or better in each eye and no binocular or accommodative dysfunction. Refractive correction was determined by objective and binocular subjective refraction. Subjects were classified into: Myopes (-0.50 to -10.00D, n=20, all contact lens wearers) or Emmetropes (Emms) (+0.50 to -0.25D). MANOVA with Bonferroni post hoc correction was used to compare the number of fixations made during 15-second periods for each activity.
Results :
Subjects made significantly fewer fixation changes for all indoor tasks (Mean 22±8 fixations), including walking indoors, compared to outdoor tasks (Mean 37±13 fixations; p<0.01), even for the same task (walk while using an iTouch indoors vs. outdoors, p=0.03).
Myopes appeared to show fewer fixation changes than Emms for all the indoor near tasks, reaching significance when playing Tetris (Myopes 19±8, Emms 24±10 fixation changes in 15sec, p=0.04) and when using an iTouch while walking indoors (Myopes 27±31, Emms 19±12, p=) or outdoors (Myopes 35±29, Emms 26±16).
When walking outdoors, myopes appeared to show more fixation changes than Emms, reaching significance when walking in a park and observing a statue (Myopes 44±24, Emms 34±22 fixation changes in 15sec, p=0.05), but not for the other tasks (Walk in park: Myopes 43±21, Emms 39±11; Walk on busy street: Myopes 43±19, Emms 37±13).
Conclusions :
Eye movements were significantly different for the indoor and outdoor tasks, with fewer fixations during indoor tasks. Data suggest that myopes may have a less dynamic visual system when doing steady near tasks such as reading or walking while using an iTouch - all tasks with higher visual demand; but not for tasks like watching TV or walking outdoors. High variability requires sampling a larger population to confirm these findings.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.