Dynamic Imaging of Ciliary Muscle and Pupil Changes During Accommodation

Abstract

Purpose : Ciliary muscle and pupil contraction are both parasympathetic responses with a common neural origin, suggesting pupil behavior may be predictive of the level of muscle activity during processes where both are activated, namely accommodation. To explore the relationship between muscle and pupil changes during accommodation, we performed dynamic imaging of the accommodative responses of the muscle and pupil with Optical Coherence Tomography (OCT).

Methods : Left eyes from 4 subjects (22, 34, 39, and 45 y/o; -2.75, -1.44, -3.31, -9.19 SEQ, respectively) were imaged using a custom-built accommodation OCT system (Ruggeri et al, Biomed Opt Exp; 2012), capturing both ciliary muscle and anterior segment response to 2D accommodative step stimuli. Cross-sectional images were acquired at 13 frames/s with 897 A-lines/frame for the ciliary muscle and 400 A-lines/frame for the anterior segment. Stimulus presentation occurred 1.54 s from the start of the trial.
Ciliary muscle maximum thickness (CMT) and pupil diameter (PD) were determined for each image. CMT was derived from manual segmentation of ciliary muscle images as the thickness measured at the muscle apex. PD was derived from automatic segmentation of anterior segment images. Changes in CMT and PD were determined as the difference between the average CMT and PD for the last and first 20 images (a sign change was applied to PD for ease of viewing).

Results : Quantification of accommodative ciliary muscle and pupil changes are detailed in Table 1. Plots of the responses of the ciliary muscle and pupil change over time during an imaging session are shown in Figure 1. Plots suggest synchronized movement of the muscle and pupil, confirmed through high cross correlation coefficients between the muscle and pupil responses.

Conclusions : Synchronization of CMT and PD during accommodation suggests pupil changes may be indicative of muscle activity and, given the role of the muscle in starting accommodation, may be further indicative of accommodative effort.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Table 1: Accommodative ciliary muscle and pupil changes for all subjects in response to a 2D step stimulus.

 

Figure 1: Plots of CM change and PD change in a 22 (A), 34 (B), 39 (C), 45 (D) y/o responding to a 2D accommodative step stimulus. Red dotted line represents onset of stimulus change. In these plots, the sign of PD change was reversed.