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Comparison of the ocular wavefront aberration between pharmacologically-induced and stimulus-driven accommodation
S Plainis1, E Plevridi, I G Pallikaris
1Institute of Vision and Optics, School of Health Sciences, University of Crete, Heraklion, Crete 71003, Greece. plainis@med.uoc.gr
Purpose:
To compare the ocular wavefront aberration between pharmacologically- and stimulus-driven accommodation in phakic eyes of young subjects.
Methods:
The aberration structure of the tested eye when accommodating was measured using the Complete Ophthalmic Analysis System (COAS; AMO WaveFront Sciences, Albuquerque, NM, USA). It was used in conjunction with a purposely-modified Badal optometer to allow blur-driven accommodation to be stimulated by a high contrast letter E with a vergence range between +0.84 D and -8.00 D. Pharmacological accommodation was induced with one drop of pilocarpine 4%. Data from six subjects (age range: 23-36 years) with dark irides were collected.
Results:
No correlation was found between the maximal levels of accommodative response achieved with an 8 D blur-driven stimulus and pharmacological stimulation. Pharmacological accommodation varied considerably among subjects: maximum accommodation, achieved within 38-85 min following application of pilocarpine, ranged from 2.7 D to 10.0 D. Furthermore, although the changes of spherical aberration and coma as a function of accommodation were indistinguishable between the two methods for low levels of response, a characteristic break in the pattern of aberration occurred at higher levels of pilocarpine-induced accommodation. This probably resulted from differences in the time course of biometric changes occurring with the two methods.
Conclusion:
Measuring the pilocarpine-induced accommodative response at only one time point after its application may lead to misleading results. The considerable inter-individual differences in the time course of drug-induced accommodative response and its magnitude may lead to overestimation or underestimation of the corresponding amplitude of normal, blur-driven accommodation. Stimulating accommodation by topical application of pilocarpine is inappropriate for evaluating the efficacy of 'accommodating' IOLs.
