Extended depth OCT imaging and biometry of the eye during accommodation as a function of subject posture

Abstract

Purpose : To evaluate the effect of subject posture on accommodation through extended depth Optical Coherence Tomography (OCT) imaging and biometry. The study will provide information on how forces applied on the lens by changing subject posture influence accommodation.

Methods : We used a custom-made extended depth SD-OCT system combined with an accommodation unit that provides monocular accommodation step stimuli (Ruggeri et al, Biomed Opt Express 3:1506-1520; 2012). The system enables dynamic imaging and full-length biometry of the eye during accommodation. The OCT delivery probe with accommodation module was secured to a slit-lamp stand to image subjects in the upright position and to a custom-made stand to image the subject in the supine and prone positions. The right eyes of three subjects (21, 22 and 23 years old) with spherical equivalent refraction ranging from -2.5 to 0 D were imaged in response to a stimulus stepping from 0 to 6 D for each of the three positions. OCT images were acquired dynamically at a frame rate of 8.7 fps over 6.2 s while the accommodation stimulus was triggered at 1.5 s after the start of an acquisition. Each acquisition consisted of 54 OCT images of the eye ranging in depth from the cornea to the retina. To quantify the change in ocular dimensions, mean and standard deviation of anterior chamber depth (ACD) and lens thickness (LT) were calculated from the first 10 OCT images acquired before the stimulus onset (relaxed state – 0D) and the last 10 OCT images acquired in the sequence (accommodated state – 6D).

Results : For each subject, mean and standard deviation of ACD and LT at different accommodative states and positions are summarized in the table below. Changes in ACD and LT during accommodation (ΔACD and ΔLT, respectively) as a function of subject and position are also shown in the graph below. There was no consistent effect on ΔACD and ΔLT across the different postures.

Conclusions : This study demonstrates the feasibility of imaging and quantifying intraocular distances dynamically during accommodation at different subject positions using extended depth OCT. Posture was found to have no effect on accommodative changes in ocular biometry.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.