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First Author: J.Pepose USA
Co Author(s): G. Zikos R. Robilotto A. Gupta M. Morris
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The purpose of this study was to establish baseline metrics of pupil light response that may serve as potential parameters for algorithmic control of electro-active intraocular lenses and to determine whether pupil light response measurements differ between cataractous and pseudophakic patients.
The study was conducted at the Institute for Vision Research at Manhattan Vision Associates in New York City.
This dual arm, parallel design study employed an infrared pupillometer (NeurOpticsTM PLR-200TM Pupillometer, NeurOptics Inc. Irvine, CA.) to measure pupil light response. Subjects were recruited during routine eye exams and did not have medical diagnoses or take medications known to affect pupil function. Arm A comprised 104 subjects (ages 60 to 79, mean = 65.8) with a diagnosis of cataracts (LOCSIII grade ?2). Arm B comprised 239 subjects (ages 60 to 80, mean = 71.3) with a history of bilateral cataract surgery via phacoemulsification with monofocal IOL implant. The time elapsed since surgery was recorded and ranged from 3 months to 16 years. Prior to measurement subjects were placed in a darkened room for 3 minutes. The pupillometer flash was set at 130 microwatts for 802 milliseconds and subjects viewed a distant fixation target. During each measurement subjects viewed a small, distant point source fixation target at the end of exam lane and measurements were recorded for the right eye including dark-adapted pupil diameter before constriction, minimum diameter of the pupil after the light flash, amplitude of pupil constriction, and average constriction velocity.
Age is a significant influence on pupil diameter in this study. Dark-adapted pupil diameter, constricted pupil diameter and amplitude of constriction were smaller while average constriction velocity was slower in older subjects. The difference between pseudophakic and cataractous subjects was not statistically significant for dark-adapted pupil size and constricted pupil diameter in an analysis of covariance that controlled for the effect of age. A significant difference between pseudophakic and cataractous subjects remained for amplitude of constriction with adjusted mean amplitude of 2.32 mm in cataractous subjects and 2.17 mm in pseudophakic subjects. The difference between age-adjusted average constriction velocities of 2.70 mm/sec and 2.59 mm/sec in cataractous and pseudophakic subjects respectively also was significant. Multiple regression of the pseudophakic subject data showed that time elapsed since surgery was a significant factor in dark-adapted pupil size and its effect is independent of age, with a regression slope of +0.034 mm per year. ANCOVA analysis with age covariate comparing cataractous subjects only to pseudophakic subjects with elapsed time since surgery less than 2.5 years showed that dark-adapted pupil diameter was significantly smaller in those pseudophakic subjects with more recent surgery.
Another study by these investigators suggests that cataract surgery has a direct effect that decreases pupil size and persists for at least 30 to 60 days. In this study, populations of cataractous patients and pseudophakic subjects with widely varying time since surgery did not have different pupil diameters, but did have a difference in amplitude of contriction and average constriction velocity. Furthermore, the dark-adapted pupil diameters in pseudophakic subjects depended on elapsed time since surgery, with a tendency of smaller pupils in early years after surgery that returns toward normal over an extended period of time. Dark-adapted pupil diameter is significantly smaller in pseudophakic subjects who had surgery less than 2.5 years ago compared to that measured in cataractous subjects after age correction. The results of the study therefore suggest that there is an effect of cataract surgery on pupil function that persists for years after surgery but gradually diminishes. The observed effect of age and time since surgery on pupil light response in pseudophakic subjects may provide a basis for customizable parameters for control algorithms being developed for electro-active intraocular lenses.
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