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H. A. Anderson; Objective Maximum Accommodative Amplitudes From Preschool to Pre-Presbyopia. Invest. Ophthalmol. Vis. Sci. 2010;51(13):805.
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Expectations of maximum accommodative amplitude in children are based upon studies of subjective push-up data. However, the subjective push-up test is not a true measurement of accommodation and over-estimates the maximum amplitude. This study measured maximum accommodative amplitudes objectively in children and adults.
Monocular maximum accommodative amplitudes were measured on the right eye of 117 subjects aged 4 to 43 years using two objective techniques (lens-stimulated and proximal-stimulated) and the subjective push-up test using a 20/40 size letter E target. For the objective techniques, 5 repeated measurements of refraction were taken at each demand presented as the subject attempted to keep the target clear. The stimulus-response function was then plotted and the maximum amplitude defined as the point at which the function peaked or reached a plateau. For lens-stimulated amplitudes, the target was placed at 33cm on the near rod of the Grand Seiko autorefractor and demand increased in 1D steps by introducing minus lenses in front of the viewing eye until the subject’s refraction showed no further increase in accommodation. For the proximal-stimulated amplitudes, demand was increased by placing the target along the near rod of the autorefractor at 7 different positions increasing from 2.5D to 8D and then along a custom built near rod attached to the forehead rest of the autorefractor for 6 positions increasing from 10.5D to 30D. For subjective amplitudes, the target was increased in proximity until the subject reported first blur and three repeated measurements were recorded.
Maximum accommodative amplitudes decreased linearly with age for all three measurement techniques (p<0.0001): Lens-Stimulated Amplitude = 8.84 - 0.13*age (R2=0.49); Proximal-Stimulated Amplitude = 10.1 - 0.16*age (R2=0.62); Subjective Push-Up Amplitude = 16.5 - 0.3*age (R2=0.54). Maximum amplitudes were lower with objective techniques for all ages and decreased at a slower rate with increasing age than the subjectively measured amplitudes. Based upon these fits, a 4 year old subject (the youngest age in this study) would be predicted to have a maximum amplitude of 15.3D with the subjective push-up test, but only 8.32 (lens-stimulated) or 9.46 (proximal-stimulated) when measured objectively.
These findings suggest that true, objectively measured maximum accommodative amplitudes are much lower in children than predicted by the traditional subjective push-up technique. These findings could have significant implications for clinical practice, such as prescribing decisions for uncorrected hyperopia in young children.
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