ABSTRACT Measurements of the resting focus of accommodation were obtained with an infrared optometer while subjects engaged in four tasks: 1) passive viewing in darkness; (2) passive vewing of a laser speckle pattern; (3) active dgment of motion in a laser speckle pattern; and (4) mental arithmetic in darkness. The results showed resting focus measures to be comparable under all four conditions for some subjects. However, other subjects exhibited consistent increases or decreases in the resting focus position when asked to judge the action of speckles within the laser test path or perform mental arithmetic. This finding suggests that “effort to see” may influence the resting focus of some subjects. Implications for measurement procedures and population estimates of the resting focus are discussed.
Post et al. (Thu,) studied this question.