July 2018
Volume 59, Issue 9
Free
ARVO Annual Meeting Abstract  |   July 2018
Investigating the functional response of cone photoreceptors during bleaching and dark adaptation with 1.7MHz optical coherence tomography
Author Affiliations & Notes
  • Mehdi Azimipour
    Department of Ophthalmology and Vision Science, University of California Davis, Sacramento, California, United States
  • Justin V Migacz
    Department of Ophthalmology and Vision Science, University of California Davis, Sacramento, California, United States
  • Brennan Marsh-Armstrong
    Department of Ophthalmology and Vision Science, University of California Davis, Sacramento, California, United States
  • Kelly S Murrell
    Department of Ophthalmology and Vision Science, University of California Davis, Sacramento, California, United States
  • Robert J Zawadzki
    Department of Ophthalmology and Vision Science, University of California Davis, Sacramento, California, United States
  • Ravi Sankar Jonnal
    Department of Ophthalmology and Vision Science, University of California Davis, Sacramento, California, United States
  • John S Werner
    Department of Ophthalmology and Vision Science, University of California Davis, Sacramento, California, United States
  • Footnotes
    Commercial Relationships   Mehdi Azimipour, None; Justin Migacz, None; Brennan Marsh-Armstrong, None; Kelly S Murrell, None; Robert Zawadzki, None; Ravi Jonnal, None; John Werner, None
  • Footnotes
    Support  NIH R01 EY 024239 (JSW) and K99 EY 026068 (RSJ).
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 295. doi:
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      Mehdi Azimipour, Justin V Migacz, Brennan Marsh-Armstrong, Kelly S Murrell, Robert J Zawadzki, Ravi Sankar Jonnal, John S Werner; Investigating the functional response of cone photoreceptors during bleaching and dark adaptation with 1.7MHz optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2018;59(9):295.

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

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Abstract

Purpose : Objective optical assessment of photoreceptor function may permit earlier diagnosis of retinal disease than current methods such as perimetry, electrophysiology, and clinical imaging. The purpose of this study is to test the hypothesis that bleaching and dark adaptation cause changes in cone outer segment (OS) length that can be measured with OCT.

Methods : A healthy subject was imaged 0.5 to 3.5 degrees temporal to the fovea, using a custom swept-source OCT system based upon a Fourier-domain mode-locked (FDML) tunable laser (λc=1063nm, Δλ=81nm;Optores GmbH), which collected A- and B-scans at rates of 1.7MHz and 2kHz, respectively. An LED-based Maxwellian stimulus channel was incorporated into the system and used to bleach the retina, with 99% of L and M photopigments bleached within 2 seconds. The subject was dark-adapted for 10 minutes prior to imaging. Two experiments were conducted. First, the subject was continuously imaged for 20 seconds (40,000 B-scans): 2 seconds prior to the flash, during a 5 second flash, and 13 seconds after the flash. Second, the subject was imaged at 20 five-second intervals starting immediately after the bleaching flash, with 1000 B-scans acquired at each interval. The inner-outer segment junction (IS/OS) and cone outer segment tips (COST) bands were segmented and average distance between the two (OS length) was calculated over a small window between 2 and 3 degrees, where OS length did not vary appreciably with eccentricity.

Results : Average OS length was 31.9μm (σ= 0.66μm) and 33.1μm (σ=1.3μm) before and after bleach, measured over two seconds before the stimulus flash and the final two seconds of the flash, respectively (p<<0.5). In the first 13 seconds following the stimulus flash the OS was observed to shorten by more than 0.5μm. In the longer experiment, the OS was observed to shorten by ~1.5μm over 100 seconds following the flash.

Conclusions : Together, these results confirm previous findings that cones elongate in response to stimulation and shorten during dark adaptation. The magnitude of length changes appears to be significantly larger than previously reported1, possibly due to differences in experimental method: we were able to measure elongation during and immediately following stimulus due to the high imaging speed and incorporation of the stimulus channel into the imaging system.
[1]Lu et al., IOVS 58:11 (2017)

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

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