July 2019
Volume 60, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2019
Optoretinogram: stimulus-induced optical changes in photoreceptors observed with phase-resolved line-scan OCT
Author Affiliations & Notes
  • Vimal Prabhu Pandiyan
    Ophthalmology, University of Washington, Seattle, Washington, United States
  • Aiden Maloney Bertelli
    Ophthalmology, University of Washington, Seattle, Washington, United States
  • James A Kuchenbecker
    Ophthalmology, University of Washington, Seattle, Washington, United States
  • B. Hyle Park
    Bioengineering, University of Calfiornia, Riverside, California, United States
  • Daniel V Palanker
    Ophthalmology, Stanford University, Stanford, California, United States
  • Austin Roorda
    School of Optometry, University of California, Berkeley, Berkeley, California, United States
  • Ramkumar Sabesan
    Ophthalmology, University of Washington, Seattle, Washington, United States
  • Footnotes
    Commercial Relationships   Vimal Prabhu Pandiyan, None; Aiden Maloney Bertelli, None; James Kuchenbecker, None; B. Hyle Park, None; Daniel Palanker, None; Austin Roorda, University of Houston (P), University of Rochester. (P); Ramkumar Sabesan, None
  • Footnotes
    Support  NIH U01EY025501, NIH R21EY027941, P30EY001730,Unrestricted grant from the Research to Prevent Blindness, Research to Prevent Blindness Career Development Award, Burroughs Welcome Fund Careers at the Scientific Interfaces, Murdock Charitable Trust, NIH R21EY025501
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 1426. doi:https://doi.org/
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      Vimal Prabhu Pandiyan, Aiden Maloney Bertelli, James A Kuchenbecker, B. Hyle Park, Daniel V Palanker, Austin Roorda, Ramkumar Sabesan; Optoretinogram: stimulus-induced optical changes in photoreceptors observed with phase-resolved line-scan OCT. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1426. doi: https://doi.org/.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : In photoreceptors, the transduction of photons to electrical signals is accompanied by nanometer-scale optical path length changes. These changes can be reliably detected using interferometric imaging of photoreceptors. Here, we characterize such light-induced changes using phase-resolved line-scan OCT.

Methods : A line-field spectral domain OCT was used to image human retina at 4 deg eccentricity through an artificial 4 mm pupil at the eye. A custom-built spectrometer with a high-speed 2D sensor enabled rapid OCT volume acquisitions at the rate of 120 - 228 Hz (8400 - 15900 B-scans/sec). Defocus was optimized using a Badal optometer. OCT volumes were acquired for 1-2 seconds after 3 mins of dark adaptation. After the 10th volume, a 660±10 nm LED flash illuminated the retina in Maxwellian view for durations between 5 and 30 ms. The acquired OCT volumes were reconstructed, registered and segmented to retrieve complex valued images corresponding to the cone inner/outer segment and outer segment tips. The averaged phase difference between them yielded optical path length change in the outer segment and this measure was inspected for its repeatability and dependence on time, stimulus intensity and stimulus size.

Results : The photoreceptors showed an exceptionally reproducible light-driven response - a 5-10 nm reduction in path length 10-20 ms after stimulus onset, followed by a continuous increase in path length saturating 300-500 ms post-stimulus. Over six repeat trials with stimulus energy of 13.7 µJ/deg2, the magnitude of maximum reduction and expansion in path length was very repeatable: 10.2 ± 3.3 nm and 152 ± 8.8 nm respectively, on average. The response saturation level scaled linearly with stimulus energy, increasing at the rate of 12.8 nm per 1 µJ/deg2. The mean amplitude and time-course of this response did not change with the stimulus area, tested in the range between 0.07 deg2 (encompassing ~12-15 cones) and 0.27 deg2.

Conclusions : Line-scan OCT offers sufficient phase stability for detecting minute stimulus-induced functional changes in outer segments of cone photoreceptors. This specific component of the optoretinogram - generally defined here as light-induced optical signals from the retina - offers a robust and sensitive biomarker for cone function in health and disease.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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