title: Accommodative hysteresis: influence on closed loop measures of far point and near point.
abstract: The study examined accommodative hysteresis under closed loop viewing conditions. After sustained focus for 8 min at either the far-point (FP) or near-point (NP) of accommodation, subjects exhibited hysteresis-like shifts in tonic accommodation, ie, dark focus (DF), in the direction of the fixation target. Measurement of NP and FP before and after the focusing period showed that only the position of the NP was significantly influenced, in a direction matching that of the DF. The NP shifted outward by 0.37 diopters (D) and inward by 0.62 D after sustained FP and NP focusing respectively. Control conditions in which subjects focused on a target at the dioptric distance of the DF or were exposed to an 8 min dark interval showed no changes in either NP, FP or DF. The ready susceptibility of the NP to hysteresis effects suggests a potential contributing role of these phenomena to near-work-induced myopia by way of increased accommodative amplitudes with attendant increases in scleral and/or choroidal stress.
mesh_terms: D000065:Accommodation, Ocular; D000293:Adolescent; D000328:Adult; D003624:Darkness; D005123:Eye / Q000294:innervation; D005403:Fixation, Ocular; D006801:Humans; D010275:Parasympathetic Nervous System / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology