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Fixation Stability with Bessel Beams

Bhattarai, Dipesh, BOptom, MPH1; Suheimat, Marwan, PhD1; Lambert, Andrew J., PhD2; Atchison, David A., DSc, FAAO1*

doi: 10.1097/OPX.0000000000001328
ORIGINAL INVESTIGATIONS

SIGNIFICANCE Ophthalmic imaging instruments that require stable fixation can benefit by using Bessel beams in the form of monitor-based Bessel images.

PURPOSE The purpose of this study was to investigate fixation stability using laser Bessel and Gaussian beams and monitor-based images of these targets.

METHODS The right eyes of 16 participants were presented with seven fixation targets: monitor-based images of a bull's eye/cross hair, a Gaussian beam, a Bessel beam with four rings and a Bessel beam with three rings; laser Gaussian beam, laser Bessel beam with four rings, and laser Bessel beam with three rings. Participants fixated target centers for five runs, in which each run presented the seven targets for 20 seconds each. An Eye Tribe tracker sampled eye positions at 30 Hz. Standard deviations along horizontal (σx) and vertical meridians (σy) and areas of bivariate contour ellipses (BCEAs) of fixation positions were calculated, and statistical significances of target differences for these parameters were determined.

RESULTS Average σx, σy, and BCEAs ranged from 0.26 to 0.35°, 0.38 to 0.55°, and 0.78 to 1.31 degrees2, respectively. Target differences in σx2 6 = 13.0, P = .04), (σy) (χ2 6 = 36.819, P < .001), and BCEA (χ2 6 = 34.406, P < .001) were statistically significant. There were significant post hoc differences between some of the target pairs for σy and BCEA, but not for σx. Monitor-based Bessel beam targets provided significantly smaller σy and BCEAs than the bull's eye/cross hair combination and the monitor- and laser-based Gaussian beam targets.

CONCLUSIONS Monitor-based images of Bessel beams provided better fixation targets than did a bull's eye/cross hair combination, monitor-based Gaussian images, and laser Gaussian beams, but no claim can be made that laser Bessel beams provide better fixation targets than do laser Gaussian beams. Monitor-based Bessel images should be useful for ophthalmic imaging instruments requiring stable fixation.

1School of Optometry and Vision Sciences and Institute of Health and Biomedical Innovation, Faculty of Health, Queensland University of Technology, Kelvin Grove, Queensland, Australia

2School of Engineering and Information Technology, University of New South Wales, Canberra, Australian Capital Territory, Australia *d.atchison@qut.edu.au

Submitted: December 10, 2017

Accepted: September 25, 2018

Funding/Support: Australian Research Council Discovery Grant (DP140101480; to DAA).

Conflict of Interest Disclosure: None of the authors have reported a financial conflict of interest. This research was supported by Australian Research Council Discovery grant DP140101480. Each of the authors had full access to the study data and take full responsibility for their presentation in this article.

Author Contributions and Acknowledgments: Conceptualization: DB, MS, AJL, DAA; Formal Analysis: DB; Funding Acquisition: AJL, DAA; Investigation: DB, MS, DAA; Methodology: DB, MS; Project Administration: DAA; Resources: DAA; Supervision: MS, DAA; Writing – Original Draft: DB, MS, AJL, DAA; Writing – Review & Editing: DB, MS, DAA.

The authors thank Dr. Fan Yi for help with extracting fixation information from instrument files.

© 2019 American Academy of Optometry