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Arne Ohlendorf, Alexander Leube, Siegfried Wahl; The effect of a cycloplegic agent on the objectively and subjectively determined refraction. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):525.
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© ARVO (1962-2015); The Authors (2016-present)
To study changes in subjective and objective refraction due to relaxed accommodation caused by an cycloplegic agent in myopes and non-myopes.
18 subjects with a mean age of 27.1 ± 3.5 years participated in the study. Refractive errors of their right eye were measured subjectively and objectively before and after a cycloplegic agent (three times one drop of 1% cycloplentolat with 10 minutes between application) was administered. Subjective refraction was performed by the same investigator, using a trial frame, trial lenses and a 4mm artificial pupil. Objective refraction was measured with the i.Profiler plus (ZEISS, Germany) before and after cycloplegia and data were analyzed for a pupil diameter of 4mm.
Objectively and subjectively determined refractions were analyzed for changes in the power vectors M, J0, J45 and the blur strength B (difference in power matrix between post- and pre-cycloplegic refraction). Using the objective refraction method, more hyperopic refractions were observed for M and B in myopes (n=10; delta M 0.44D ± 0.38D, p<0.01 and B 0.49 ± 0.34D, p<0.01) and non-myopes (n=8; delta M 1.12D ± 0.62D, p<0.01 and B 1.14 0.61, p<0.01). Changes in objectively determined J0 and J45 were minor and lacked statistical significance, in both groups. Also, subjectively measured refraction showed a significant shift towards more hyperopia in non-myopes (delta M 0.84D ± 0.68D, p<0.05 and B 0.89 ± 0.62, p<0.001), while J0 and J45 were unaffected. In myopes, blur strength B showed significant changes, again towards hyperopia (0.36 ± 0.24, p<0.01), while changes in power vectors M, J0 and J45 lacked statistical significance.
Mean spherical equivalent and blur strength shifted positively after cycloplegia when refraction was assessed subjectively and objectively for the same pupil size. The cycloplegic effect of the drug should be taken into account when interpreting refraction measurements for the prescription of spectacles, planning a wavefront-guided laser ablation or cataract surgery. Possible influence of changes in axial length or choroidal thickness may account for the observed differences but were not investigated in the current course of the study.
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