Monocular accommodation response for totally occluded objects.

Abstract

PURPOSE: To investigate the accuracy and stability of the monocular accommodation response when attention is directed toward a totally occluded distant object. METHODS: A static infrared optometer was used to measure the monocular accommodative response in 16 participants while they viewed a distant letter target in the presence or absence of an intervening object that totally occluded the distant target from view. Participants were instructed to attend to and focus for the distant target. RESULTS: Participants differed widely in their accommodative responses for a totally occluded distant object, focusing close to the distant object, close to the intervening object, in between the two objects, and beyond the distant object. Some of this variability could be attributed to individual differences in the dark focus. Accommodation was more variable when the distant target was totally occluded by an obstruction at an intermediate distance (50 cm). CONCLUSIONS: Many individuals focus poorly in the presence of a visual obstruction that totally occludes the object of regard.