July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
Measuring local flicker evoked changes in retinal capillary blood flow using a dual-beam Adaptive Optics Scanning Laser Ophthalmoscope
Author Affiliations & Notes
  • Raymond Luval Warner
    Optometry, Indiana University, Bloomington, Bloomington, Indiana, United States
  • Alberto De Castro
    Universidad de Murcia, Murcia, Spain
  • Ting Luo
    Optometry, Indiana University, Bloomington, Bloomington, Indiana, United States
  • Kaitlyn Sapoznik
    Optometry, Indiana University, Bloomington, Bloomington, Indiana, United States
  • Lucie Sawides
    Universidad de Murcia, Murcia, Spain
  • Stephen A Burns
    Optometry, Indiana University, Bloomington, Bloomington, Indiana, United States
  • Footnotes
    Commercial Relationships   Raymond Warner, None; Alberto De Castro, None; Ting Luo, None; Kaitlyn Sapoznik, None; Lucie Sawides, None; Stephen Burns, None
  • Footnotes
    Support  NIH/NEI 1R0EY024315
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 647. doi:
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      Raymond Luval Warner, Alberto De Castro, Ting Luo, Kaitlyn Sapoznik, Lucie Sawides, Stephen A Burns; Measuring local flicker evoked changes in retinal capillary blood flow using a dual-beam Adaptive Optics Scanning Laser Ophthalmoscope. Invest. Ophthalmol. Vis. Sci. 2018;59(9):647.

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

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Abstract

Purpose : Areas of increased neural activity have higher metabolic demands. For sufficient oxygen and glucose to be delivered by the blood, dilation of nearby vessels occurs -a process known as neurovascular coupling. Here, we use the dual-beam Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO) to measure changes in the velocity of capillary red blood cells with local flicker stimulation.

Methods : The retina of four healthy subjects (ages 24-63) were imaged with a dual-beam AOSLO. Imaging beams were offset 50 lines vertically to produce a temporal separation of 3.12 ms. Parafoveal capillaries were imaged simultaneously in two channels, each having a 500 µm offset aperture, in three sets of three 1-minute sessions. The first session included 1 minute of No Flicker (uniform field), followed by 1 minute of 2°x2° flicker stimulation (10 Hz rate) 4° from the region of interest (ROI), and ending with 1 minute uniform field again in 3 second 100 frame videos. The same procedure was repeated with the flicker stimulation displaced 2°, and 0° from the ROI.
Capillary red blood cells (RBCs) were identified using a local-temporal variance mask, and the local average cell displacement between the two imaging fields was computed over the 3 second measurement within approximately 100 ms averaging window.

Results : Capillary blood flow was measureable in all four subjects. As expected, velocity and pulsatility varied among individual capillaries and between subjects. There was an interaction of velocity and distance between the ROI and flicker stimulation. All 4 subjects showed a decrease in RBC velocity from the uniform field to flicker stimulation and then a return towards the baseline velocity after flicker ceased (1.82 mm/s to 1.41 mm/s, then back to 1.56 mm/s after flicker). At a distance of 2°, there was little effect of flicker and for the superimposed flicker, 3 out of the 4 subjects showed an increase in RBC velocity from 1.45 mm/s to 1.64 mm/s.

Conclusions : The dual-beam AOSLO allows us to measure RBC velocities in human retinal capillaries and observe changes in average velocities in all subjects. The results are consistent with a process of active distribution of blood flow based on local demand and improve our understanding of neurovascular coupling in the retina.

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

 

The location of flicker stimulation for each imaging session at 4° (P.1), 2° (P.2), and 0° (P.3) from ROI.

The location of flicker stimulation for each imaging session at 4° (P.1), 2° (P.2), and 0° (P.3) from ROI.

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