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First Author: E.Donnenfeld USA
Co Author(s): A. Gupta M. Morris G. Zikos R. Robilotto
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The purpose of this study was to determine the effect of cataract surgery on pupil diameter and pupil constriction.
The study was conducted at the Institute for Vision Research at Manhattan Vision Associates in New York, NY and the California Eye Institute in Fresno, CA USA. Cataract surgery was performed independently from the investigation by multiple surgeons at Ophthalmic Consultants of Long Island, NY, California Eye Institute, CA, Laser & Microsurgery Institute, NY, and Eastside Eye Associates, NY USA.
This single arm prospective, longitudinal study examined pupil light response using an infrared pupillometer (NeurOpticsTM PLR-200TM Pupillometer, NeurOptics Inc. Irvine, CA.) pre- and post cataract surgery. 44 subjects, ages 61 to 80 were examined before and after bilateral phacoemulsification with implantation of a monofocal intraocular lens. None of the patients had a medical diagnosis or took medications known to affect pupil function. Post-surgery measurements were made between 30-60 days after successful bilateral cataract surgery. Prior to pupillary measurement, subjects were placed in a darkened room (<1.0 Lux) for 3 minutes. The instrument flash was set at default values of 130 microwatts for 802 milliseconds. During each measurement subjects viewed a small, distant red/green point source fixation target (<0.5 cd/m2) at the end of exam lane and measurements were recorded for the right eye. Pupil measurements that were evaluated included dark-adapted maximum pupil diameter, minimum pupil diameter after constriction caused by the light flash, the change in pupil diameter caused by the light flash and the average constriction velocity.
Repeated measures ANOVA shows that pupil diameters measured after cataract surgery were significantly smaller than before surgery. Mean pupil diameter after dark adaptation was 5.36 mm before surgery and 4.85 mm after (p<.001). Mean post-surgery diameter after light flash was 3.20 mm prior to surgery and 2.94 mm after (p < .001). Mean pupil constriction prior to surgery was 2.16 mm and 1.90 mm after surgery (p<.001). Average constriction velocity was 2.58 mm/sec prior to surgery and 2.49 mm/sec after (p=.03). Linear regression ANOVA showed significant correlations between pre- and post-surgery measurements of dark adapted pupil diameter (r2 = .76, p<.001), pupil diameter after flash (r2=.63, p<.001), magnitude of pupil constriction (r2=.72, p<.001) and average constriction velocity (r2=.59, p<.001). Inspection of vectors showing the magnitude of change of dark-adapted and flash response pupil sizes associated with surgery suggests that a subset of patients with the smallest pupils had a response that differs from the majority of patients. Although a small effect of age was observed with slightly less constriction associated with increasing age, the magnitude of the change of pupil diameters associated with cataract surgery was similar across all observed ages.
Scotopic pupil size, pupil constriction to a photopic stimulus, and pupil constriction velocity were all significantly reduced following cataract surgery and measurements before and after surgery were significantly correlated. Previous studies have been ambiguous regarding the effect of cataract surgery on pupil size, reporting either no change or transient changes that disappeared within 30 days. In this study the significant effect on pupil size and constriction velocity persisted at least one to two month. The change in pupil dynamics following cataract surgery may have an effect on monofocal/multifocal/accommodating IOL design or the development of control algorithms for electro-active intraocular lenses.
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