Abstract

A scanning laser ophthalmoscope with an integrated retinal tracker (TSLO) was designed, constructed, and tested in human subjects without mydriasis. The TSLO collected infrared images at a wavelength of 780 nm while compensating for all transverse eye movements. An active, high-speed, hardware-based tracker was able to lock onto many common features in the fundus, including the optic nerve head, blood vessel junctions, hypopigmentation, and the foveal pit. The TSLO has a system bandwidth of ∼1 kHz and robustly tracked rapid and large saccades of approximately 500 deg/sec with an accuracy of 0.05 deg. Image stabilization with retinal tracking greatly improves the clinical potential of the scanning laser ophthalmoscope for imaging where fixation is difficult or impossible and for diagnostic applications that require long duration exposures to collect meaningful information.

© 2002 Optical Society of America

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References

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Acta Otolaryngol. (1)

H. Scherer, W. Teiwes, and A. H. Clarke, �??Measuring three dimensions of eye movement in dynamic situations by means of videooculography,�?? Acta Otolaryngol. 111, 182-187 (1991).
[CrossRef] [PubMed]

Appl. Opt. (2)

D. P. Wornson, G. W. Hughes, and R. H. Webb, �??Fundus tracking with the scanning laser ophthalmoscope,�?? Appl. Opt. 26, 1500-1504 (1987).
[CrossRef] [PubMed]

D. X. Hammer, R. D. Ferguson, J. C. Magill, M. A. White, A. E. Elsner, and R. H. Webb, �??Compact scanning laser ophthalmoscope with high-speed retinal tracker,�?? Appl. Opt., submitted.

Exp. Brain Res. (1)

D. P. Munoz, J. R. Broughton, J. E. Goldring, and I. T. Armstrong, �??Age-related performance of human subjects on saccadic eye movement tasks,�?? Exp. Brain Res. 121, 391-400 (1998).
[CrossRef] [PubMed]

J. Biomed. Opt. (1)

E. Naess, T.Molvik, D. Ludwig, S. Barrett, S. Legowski, C. Wright, and P. de Graaf, �??Computerassisted laser photocoagulation of the retina - a hybrid tracking approach,�?? J. Biomed. Opt. 7 179-189 (2002).
[CrossRef] [PubMed]

J. Opt. Soc. Am. (2)

D. H. Kelly, H. D. Crane, J. W. Hill, and T. N. Cornsweet, �??Non-contact method of measuring small eye movements and stabilizing the retinal image,�?? J. Opt. Soc. Am. 59, 509 (1969).

T. N. Cornsweet and H. D. Crane, �??Servo-controlled infrared optometer,�?? J. Opt. Soc. Am. 60, 548-554 (1970).
[CrossRef] [PubMed]

J. Refract. Surg. (1)

R. R. Krueger, �??In Perspective: Eye Tracking and Autonomous Laser Radar,�?? J. Refract. Surg. 145-149 (1999).
[PubMed]

Opt. Express (2)

Other (2)

R. Daniel Ferguson, �??Line-scan laser ophthalmoscope,�?? U. S. Patent pending.

R. Daniel Ferguson, �??Servo tracking system utilizing phase-sensitive detection of reflectance variation,�?? U. S. Patents #5,767,941 and #5,943,115.

Supplementary Material (4)

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Figures (7)

Fig. 1.
Fig. 1.

General optical layout of TSLO. OL: ophthalmic lens, SL: f/2 scan lens, TG: tracking galvanometers, DS: dither scanners, TR: tracking reflectometer, IG: imaging galvanometer, LD: laser diode imaging source, L: f/2 lens, det: detector.

Fig. 2.
Fig. 2.

Rapid eye motion can create problems for software-based retinal trackers. (a) Single frame of fundus when eye is stationary, (b) single frame when eye slews in the opposite direction as the image scanner, (c) single frame when eye slews in the same direction as the image scanner, and (d) single frame when eye slews in a direction perpendicular to the image scan. Acquisition rate was 30 frames/sec.

Fig. 3.
Fig. 3.

Comparison of 90 frames (6 sec) co-added for a single subject (a) without tracking and fixation (moderate saccades), (b) without tracking but with fixation, (c) with tracking and fixation, and (d) with tracking but without fixation. Line indicates cross-sections used for measurement of motion blur.

Fig. 4.
Fig. 4.

(2.3 Mb) Tracking during large, fast saccades (∼300 deg/sec). Eye x- and y-positions acquired from galvanometers are shown in graphs beside video. Tracking point (circles indicate dither beam radius and amplitude) and fovea (arrow) are denoted. Still image is co-added frames over the duration of the video. Acquisition rate was 15 frames/sec.

Fig. 5.
Fig. 5.

(2.7 Mb) Tracking on retinal blood vessel junctions. Annotated as Fig. 4.

Fig. 6.
Fig. 6.

(2.1 Mb) Tracking on a region of hypopigmentation. Annotated as Fig. 4.

Fig. 7.
Fig. 7.

(1.6 Mb) Tracking on the foveal pit. Annotated as Fig. 4.

Tables (1)

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Table 1. Cross-sectional analysis of vessel width.

Metrics