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Size of stimulus of fixation and far accommodative response

SUMMARY

The far focus of 23 normal subjects was measured, at 4 meters, with the Canon R-1®. Optotypes with two different sizes (20/30 and 20/100) were used as fixation stimuli. With the 20/100 optotypes the mean accommodative response was equal to the distance requirement (0.25D) . With the 20/30 optotypes there was an accommodative lead of 0.24D . The differences in far focus were not correlated with the magnitude of darkfocus. The effect of optotype size on accommodation may be similar to the effect of mental activity.

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