title: Aspects of tonic accommodation in emmetropia and late-onset myopia.
abstract: An objective infrared optometer was used to investigate the influence of cognitive demand on tonic accommodation (TA) for two groups of young emmetropes (N = 15) and late-onset myopes (N = 15). TA was measured under a passive condition and while subjects carried out a reverse counting task. The TA of myopes under the passive condition (mean = 0.81 D, SD = 0.46 D) was shown to have lower values than the TA of emmetropes (mean = 1.14 D, SD = 0.46 D). For the myopic group the counting task induced a positive shift in TA (mean = +0.35 D, SD = 0.31 D) that was significantly higher than that for the emmetropic group (mean = +0.07 D, SD = 0.27 D). The implications for theories of refractive error development are discussed.
mesh_terms: D000065:Accommodation, Ocular; D000328:Adult; D006801:Humans; D008297:Male; D009216:Myopia / Q000503:physiopathology*; D012029:Refraction, Ocular; D012146:Rest; D013850:Thinking; D013997:Time Factors