Pharmacological pupil dilation causes significant sensitivity changes that are pupil change-dependent but not eccentricity-dependent

Abstract

Purpose : It is not known if there are systematic, location-specific changes in sensitivity that are dependent on pupil size change across the visual field (VF) following pharmacological pupil dilation. We first aimed to determine if eccentricity-dependent effects exist through linear regression analysis of sensitivity changes at various eccentricities. We then used a clustering algorithm to identify if there were areas of similar sensitivity change across the VF.

Methods : Fifty three normal subjects underwent testing on the Humphrey Field Analyzer 30-2 test grid in full threshold mode with a Goldmann size III stimulus, twice prior to and following dilation with tropicamide 0.5%. Change in sensitivity at various eccentricities were analyzed and pooled by the subject’s initial pupil size (4-5mm, 5-6mm, and 6+mm). Point-wise changes in sensitivities were converted into grayscale pixel values (PVs) and analyzed using pattern recognition (unsupervised classification using ISODATA clustering) to identify regions of similar change, producing theme maps with classes representing similar sensitivity change.

Results : Significantly more points showed worsening than improvement beyond the ±3dB expected intraobserver variability (average p-value = 0.018). Greater worsening of sensitivity occurred with a larger change in pupil size. There was no significant difference between the amount of change at varying concentric rings across all groups (average p-value = 0.427), and also no eccentricity-dependent effect (average p-value = 0.830). Pattern recognition analysis was concordant as it showed no systematic patterns of location-specific sensitivity change for all pupil size groups.

Conclusions : All subjects had a significant number of locations exhibiting sensitivity changes >3dB after dilation. Starting pupil sizes of 4-5mm have the greatest propensity to exhibit significant sensitivity changes, as there is greater potential for pupil size changes with dilation. However, no systematic, location-specific sensitivity change across the 30-2 test grid was identified.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

A: Sensitivity change as a function of change in pupil size for initial pupil sizes of 4-5mm, color-coded by eccentricity (average slope -1.34 dB/mm). B: Difference in dB were converted to grayscale PVs. Pattern recognition generated a pseudocolor theme map showing areas with similar sensitivity change.