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Molly K Lalonde, Alyssa Gehring, Tawna L Roberts; Impact of Cognitive Effort on Accommodation and Pupil Size in Adults. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2942.
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Changes in accommodation and pupil size have been shown to be negatively correlated as an increase in accommodative response is related to a decrease in pupil size. However, studies of the impact of cognition on accommodation and pupil size have demonstrated conflicting results. Studies of the impact of cognition on pupil size have shown that increase in cognitive effort results in an increase in pupil size, whereas studies of cognitive effort on accommodation have shown that increased cognitive effort may result in an increase in accommodtiave response, suggesting a negative correlation. The purpose of the study was to prospectively investigate the impact of cognitive effort on accommodation and pupil size simultaneously during passive and cognitive tasks of different letter sizes.
Accommodation was measured for 30 seconds monocularly in the right eye at 33 cm using the PowerRef 3 (50 Hz) in 21 adults (18-34 years) in 4 separate viewing tasks that varied in cognitive demand and letter size (passive 20/50 and 20/100; active 20/50 and 20/100). For all tasks, the stimuli consisted of 9 numbers arranged in 3x3 rows. The numbers refreshed every 10 seconds for a total of 30 seconds. For the passive tasks, subjects were instructed to simply look at the numbers. For the active tasks, the subjects were instructed to add each set of numbers silently in rows then columns. Outcome variables, pupil size and accommodation, were compared between the passive and active tasks for each letter size using paired t-tests.
A significant difference in accommodation was not detected (p>0.05) between the cognitive and passive tasks for the 20/50 size stimuli (Cognitive: -1.75±0.39, Passive: -1.75±0.37) or the 20/100 size stimuli (Cognitive: -1.73±0.35, Passive: -1.70±0.33). Pupil size was significantly larger in the cognitive task than the passive task for both the 20/50 size stimuli (Cognitive: 6.24±0.694, Passive: 5.80±0.80, p<0.001) and the 20/100 size stimuli (Cognitive: 6.24±0.74, Passive: 5.94±0.69, p<0.001).
In adults, cognitive effort did not affect the accommodative response at either 20/50 or 20/100 sized stimuli. However, pupil size was significantly larger during the cognitive task than the passive task for both letter sizes tested. The results suggest that pupil size may be affected by increased cognitive effort independent of accommodation and stimulus size.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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