June 2020
Volume 61, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2020
Diameter dependence of dual-wavelength retinal oximetry
Author Affiliations & Notes
  • Lucas William Rowe
    Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Julia Arciero
    IUPUI, Indiana, United States
  • Alon Harris
    Icahn School of Medicine at Mount Sinai Hospital, New York, United States
  • Brent A Siesky
    Icahn School of Medicine at Mount Sinai Hospital, New York, United States
  • Alice Chandra Verticchio Vercellin
    Icahn School of Medicine at Mount Sinai Hospital, New York, United States
    University of Pavia, Italy
  • Sunu Mathew
    Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States
  • James M Beach
    Center for Drug Design, University of Minnesota, Minnesota, United States
  • Footnotes
    Commercial Relationships   Lucas Rowe, None; Julia Arciero, None; Alon Harris, AdOM (C), AdOM (I), AdOM (S), AdOM (R), LuSeed (I), Oxymap (I), Thea (R); Brent Siesky, None; Alice Chandra Verticchio Vercellin, None; Sunu Mathew, None; James Beach, Oxymap (I)
  • Footnotes
    Support  R01EY030851 (Integration of clinical measures and theoretical modeling to quantify sectorial specific changes in ocular structure, function, and hemodynamics) and NSF-DMS 1853222/1853303
Investigative Ophthalmology & Visual Science June 2020, Vol.61, 494. doi:
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    • Get Citation

      Lucas William Rowe, Julia Arciero, Alon Harris, Brent A Siesky, Alice Chandra Verticchio Vercellin, Sunu Mathew, James M Beach; Diameter dependence of dual-wavelength retinal oximetry. Invest. Ophthalmol. Vis. Sci. 2020;61(7):494.

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

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Abstract

Purpose : Retinal vessel oxygen saturation obtained by dual-wavelength oximetry shows a dependence on vessel diameter where measured saturation is increased in smaller vessels. This dependence is considered an artifact of measurement since hemodynamic considerations cannot explain it. This study aims at understanding the artifact as a consequence of vessel light transmission and reflectance from retinal tissue.

Methods : Retinal oximetry data were compared with outcomes from a model of tissue reflectance (Kubelka Munk, KM). KM defines the retinal vessel as a slab of infinite extent over the retina, and thus considers only double-pass transmission (transmission to and from retina behind vessel) and back-scatter by lumenal blood. KM predicts that vessel reflectance, and ultimately measured saturation, follows a nonlinear (hyperbolic) relationship with vessel diameter. Light intensity returned from first and higher-order vessels (Iv) and from adjacent retina was extracted (Oxymap Analyzer) from dual-wavelength oximetry images. Vessel reflectance (Rv) was defined by the relationship Rv = Iv / Io, where illumination intensity Io was determined such that for large vessel diameter (>150 mm), vessel reflectance matched the theoretical reflectance predicted by KM.

Results : At the oximetry measurement wavelength (600 nm), there was close agreement across the sampled diameter range (20-200 mm) between KM reflectance and experimental arteriolar and venular reflectance. At reference wavelength (570 nm), for diameters below 90 mm, the experimental reflectance from both vessel types exceeded by as much as 1.4x the model prediction (Fig. 1).

Conclusions : Agreement between oximetry data and KM supports the role of double-pass transmission as a source of diameter sensitivity. As diameter decreases, reflectance behind the vessel becomes important, increasing Iv, which ultimately raises measured saturation. Smaller diameter also allows single-pass transmission through the vessel which is a departure from the KM model. At low absorption (600 nm) the contribution is weak since there is nearly equal light return inside and outside vessels. At high absorption (570 nm), single-pass transmission raises vessel reflectance above the model prediction.

This is a 2020 ARVO Annual Meeting abstract.

 

Figure 1. Venule reflectance values (points) and KM model (dashed lines): 600 nm (upper) and 570 nm (lower).

Figure 1. Venule reflectance values (points) and KM model (dashed lines): 600 nm (upper) and 570 nm (lower).

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