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M. Baumeister, M. Wendt, A. Glasser; Accommodative Dynamics in Middle–Aged Rhesus Monkeys . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3890.
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© ARVO (1962-2015); The Authors (2016-present)
Prior studies of Edinger–Westphal (EW) stimulated accommodation in anesthetized adolescent rhesus monkeys show that peak velocity of accommodative responses are linearly related to amplitude over the full accommodative range available. Here, the relationships between peak velocity and amplitude of accommodation and disaccommodation are investigated in older monkeys to explore the effects of aging on accommodative dynamics.
Three eyes of 3 iridectomized rhesus monkeys (18.6 years, 15.3 years and 14.6 years old) were studied. Accommodation was elicited by stimulation of the EW nucleus with increasing stimulus amplitudes, including supramaximal stimulus amplitudes greater than that required to achieve the maximum response. Refraction was recorded dynamically using infrared photorefraction. Exponential functions were fit to the dynamic accommodative and disaccommodative responses and peak velocities were obtained from the derivatives of the functions.
Maximum accommodative amplitude was 5.75±0.22 D (mean±SD) with a mean maximum peak velocity of accommodation of 15.59±0.57 D/s. Maximum peak velocity of disaccommodation was 36.61±8.67 D/s for the maximum disaccommodative amplitude of 5.06±0.88 D. The peak velocity of accommodation increased linearly with amplitude (slope: 2.72, intercept: 0.66, r²: 0.96, p<0.001). For supramaximal stimulus amplitudes, peak velocities of accommodation continued to increase with stimulus amplitude, without a further increase in response amplitude. The peak velocity of disaccommodation increased linearly up to the maximum disaccommodation amplitude (slope: 7.70, intercept: –3.33, r²: 0.92, p<0.001) with no further increase with supramaximal stimulus amplitudes. Comparing these results in middle aged monkeys with those from younger monkeys in a prior study (Vilupuru & Glasser, 2002) shows that, in younger, adolescent monkeys, 5.75 D of accommodation produced a peak velocity of 13.83 D/s and 5.06 D of disaccommodation produced a peak velocity of 30.96 D/s.
In EW–stimulated accommodation in middle–aged rhesus monkeys with reduced accommodative amplitudes, peak velocities of accommodation and disaccommodation increase linearly with response amplitude over the full response range available. Greater peak velocities can be achieved with supramaximal stimulation. Although maximum response amplitude is reduced in older monkeys, middle–aged and adolescent rhesus monkeys achieve similar accommodative and disaccommodative peak velocities for the same response amplitudes.
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