Area of Concentration (Petal): Basic, Clinical, Translational Science

Specialty: Ophthalmology

Keywords: ocular biomechanics, optic nerve head, ocular pulse

Background:  Previous studies have demonstrated that the ocular pulse that results from cardiac contractions may cause deformations of structures behind the eye, but it has primarily been studied in central gaze and in abduction. In this current study, we explored the effects of ocular pulse on mechanical strain in the ocular tissues during horizontal and vertical eye movements.

Objective: To evaluate the effect of ocular pulses on mechanical strain during horizontal and vertical eye rotations.

Methods: A confocal scanning laser ophthalmoscope was used to acquire infrared video sequences of the optic disc region during maintained horizontal and vertical eye gaze fixations. Thirteen images were generated from the videos in each gaze position. Sequential images were compared over the cardiac cycle per gaze to evaluate the effect of ocular pulse on mechanical strain.  Local tissue deformations during eye movements were tracked using automated image registration followed by learning-based optical flow analysis. The images were divided into four concentric regions extending from the optic disc each measuring one disc radius.

Results: Eight participants (5 males, 3 females) were included, contributing a total of 16 eyes.  The mean age was 37± 15 years.  When analyzing all regions across each of the 5 gazes in both the X and Y axes, the average maximum difference in optical strain between images taken within the same gaze per participant was 0.17%, while the minimum difference observed was 0.06%

Conclusions

The effect of the ocular pulse on the mechanical strain is likely negligible during horizontal and vertical eye movements. This means that transmitted cardiac pulse is unlikely to confound analysis of mechanical strain produced by eye movements themselves. This simplifies the analysis of these effects.