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Abstract
The nominally steady-state accommodation response exhibits temporal variations which
can be characterized by two dominant regions of activity; a low frequency component
(LFC < 0.6 Hz) and a high frequency component (1.0 < or = HFC < or = 2.1 Hz). There
is no consensus as to the relative contribution made by each of the frequency components
of the microfluctuations to the control of steady-state accommodation. We investigate
the effect of variations in artificial pupil diameter (0.5, 1, 2, 3, 4 and 5 mm pupils)
on the microfluctuations of accommodation, while three young emmetropic subjects view,
monocularly, a photopic high contrast Maltese cross target placed at a dioptric distance
equal to their open-loop accommodation level. Average power spectra were calculated
for five accommodation signals, each of 10 sec duration, collected for each viewing
condition at a sampling rate of 102.4 Hz using a continuously recording infrared objective
optometer. For artificial pupil diameters < or = 2 mm the power of the LFC was found
to increase as a function of reducing pupil diameter, while for artificial pupil diameters
> 2 mm the LFC was found to be relatively constant. No systematic change in the HFC
with varying artificial pupil diameter was observed. Changes in the root-mean-square
(r.m.s.) value of the fluctuations with varying pupil diameter were significant (one-way
ANOVA, F = 8.507, P = 0.0001, d.f. = 89) and showed a similar form to the changes
in the LFC.(ABSTRACT TRUNCATED AT 250 WORDS)