Adaptive optics optical coherence tomography for measuring phase and reflectance dynamics of photoreceptors

Omer P. Kocaoglu; Ravi S. Jonnal; Sangyeol Lee; Qiang Wang; Zhuolin Liu; Donald T. Miller

doi:10.1117/12.910530

9 March 2012 Adaptive optics optical coherence tomography for measuring phase and reflectance dynamics of photoreceptors

Omer P. Kocaoglu, Ravi S. Jonnal, Sangyeol Lee, Qiang Wang, Zhuolin Liu, Donald T. Miller

Author Affiliations +

Proceedings Volume 8209, Ophthalmic Technologies XXII; 82091I (2012) https://doi.org/10.1117/12.910530
Event: SPIE BiOS, 2012, San Francisco, California, United States

Abstract

Optical coherence tomography with adaptive optics (AO-OCT) is a noninvasive method for imaging the living retina at the microscopic level. We used AO-OCT technology to follow changes in cone photoreceptor outer segment (OS) length and reflectance. To substantially increase sensitivity of the length measurements, a novel phase retrieval technique was demonstrated, capable of detecting changes on a nanometer scale. We acquired volume videos of 0.65°x0.65° retinal patches at 1.5° temporal to the fovea over 75 and 105 minutes in two subjects. Volumes were dewarped and registered, after which the cone intensity, OS length, and referenced phase difference were tracked over time. The reflections from inner segment/OS junction (IS/OS) and posterior tips of OS (PT) showed significant intensity variations over time. In contrast, the OS length as measured from the intensity images did not change, indicative of a highly stable OS length at least down to the level of the system's axial resolution (3μm). Smaller axial changes, however, were detected with our phase retrieval technique. Specifically, the PT-IS/OS phase difference for the same cones showed significant variation, suggesting real sub-wavelength changes in OS length of 125±46 nm/hr for the 22 cones followed. We believe these length changes are due to the normal renewal process of the cone OS that elongate the OS at a rate of about 100 nm/hr. The phase difference measurements were strongly correlated among Alines within the same cone (0.65 radians standard deviation) corresponding to a length sensitivity of 31 nm, or ~100 times smaller than the axial resolution of our system.

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Omer P. Kocaoglu, Ravi S. Jonnal, Sangyeol Lee, Qiang Wang, Zhuolin Liu, and Donald T. Miller "Adaptive optics optical coherence tomography for measuring phase and reflectance dynamics of photoreceptors", Proc. SPIE 8209, Ophthalmic Technologies XXII, 82091I (9 March 2012); https://doi.org/10.1117/12.910530

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Adaptive optics optical coherence tomography

Phase measurement

Reflectivity

Optical coherence tomography

Image resolution

Adaptive optics

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