Dynamic Interaction of the Ciliary Muscle and Crystalline Lens during Accommodation evaluated with SD-OCT

Abstract

Purpose : To evaluate the dynamic interaction between the human ciliary muscle and crystalline lens during accommodation using SD-OCT.

Methods : We combined and synchronized two SD-OCT systems individually operating at 840nm and 1325nm and an accommodation unit that provides monocular accommodation step stimuli. Imaging of the anterior segment including cornea, anterior chamber and crystalline lens was performed with the SD-OCT system at 840nm. The SD-OCT system at 1325nm was used for transscleral imaging of the ciliary muscle. The two SD-OCT systems enable simultaneous and synchronized acquisition of two OCT image sequences of, respectively, the ciliary muscle and the crystalline lens at an imaging speed of 13 frames per second. The response to an accommodative step stimulus varying between 0D and 2D was imaged in the left eye of a 22 and a 45 year-old subjects. Each OCT image sequence consisted of 80 frames. Segmentation and distortion correction of the ocular boundaries was performed on each OCT frame to extract the time dependent crystalline lens thickness (LT) and ciliary muscle maximum thickness (CMT).

Results : The system displays the synchronous response of the ciliary muscle and crystalline lens in real-time. Graphs plotting the dynamic changes of LT in function of CMT (ΔLT vs. ΔCMT) during accommodation were obtained. At the end of the accommodative process, the mean ΔCMT and ΔLT were, respectively, 0.045mm and 0.125mm for the 22 year-old subject and 0.107mm and 0.090mm for the 45 year-old subject. We calculated the ratio ΔLT/ΔCMT during dynamic accommodation as the slope of the linear regression of the data points (ΔCMT, ΔLT) during the rising phase of the lens thickness. ΔLT/ΔCMT was 2.268 in the 22 year-old subject and 0.746 in the 45 year-old subject. The change in ciliary muscle thickness required to elicit a ΔLT of 5% during the initial stage of the rising phase (ΔCMT_ΔLT5%) was 0.005mm and 0.034mm for the 22 and the 45 year-old subject, respectively.

Conclusions : This study demonstrates the feasibility of imaging and quantifying the interaction between the ciliary muscle and crystalline lens during accommodation in subjects with different ages. The preliminary results suggest that a larger effort of the ciliary muscle is required to elicit the same change in lens thickness in an older lens.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.