June 2020
Volume 61, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2020
Measurement of absolute episcleral flow rates in human glaucoma subjects and control
Author Affiliations & Notes
  • Ashley Park
    University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Jessica Pottenburgh
    University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Samuel Asanad
    University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Ahmed Siddiqui
    University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Lakyn Mayo
    University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Osamah Saeedi
    University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Footnotes
    Commercial Relationships   Ashley Park, None; Jessica Pottenburgh, None; Samuel Asanad, None; Ahmed Siddiqui, None; Lakyn Mayo, None; Osamah Saeedi, None
  • Footnotes
    Support  Fight for Sight
Investigative Ophthalmology & Visual Science June 2020, Vol.61, 612. doi:
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      Ashley Park, Jessica Pottenburgh, Samuel Asanad, Ahmed Siddiqui, Lakyn Mayo, Osamah Saeedi; Measurement of absolute episcleral flow rates in human glaucoma subjects and control. Invest. Ophthalmol. Vis. Sci. 2020;61(7):612.

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

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Abstract

Purpose : Absolute and reliable quantification of episcleral venous and arterial flow rates may allow for a better understanding of aqueous outflow and ultimately serve as a reliable biomarker to guide pre-operative planning or intraoperative decision making for minimally invasive glaucoma surgeries (MiGS). Erythrocyte-mediated angiography (EMA) is a novel method that allows direct visualization of individual erythrocytes within the ocular microvasculature in vivo (Wang et al, Biomedical Optics Express, 2019). We utilized EMA to accurately quantify blood flow in episcleral veins and arteries.

Methods : Blood velocities were measured from 3 episcleral veins of 3 subjects (glaucoma, glaucoma suspect, control) and 1 episcleral artery (glaucoma suspect) using EMA episcleral angiograms acquired with a Heidelberg scanning laser ophthalmoscope at 24.6 frames per second. Diameters of episcleral vessels of interest were measured using conventional ICG angiograms (Figure 1). A semi-automated MATLAB program was used to identify and track individual erythrocytes. An ophthalmic instrument of known diameter was used to establish a scale. Flow rates were calculated by multiplying the cross-sectional area of the vessel averaged in systole and diastole by its velocity.

Results : Mean episcleral venous velocities varied from 1.665mm/sec to 5.627mm/sec. Mean episcleral venous flow rates ranged from 0.004 mm3/sec to 0.043 mm3/sec. Mean arterial flow velocity was 9.56 mm/sec and flow rate was 0.094 mm3/sec.

Conclusions : Our measurements are comparable to episcleral velocities determined from prior studies (Ueda, Ophthalmology and Therapy, 2018). By incorporating diameter, we describe for the first time to our knowledge, quantitative measurements of absolute episcleral flow in human control and glaucoma subjects. As expected, episcleral arterial flow was greater than venous flow.

This is a 2020 ARVO Annual Meeting abstract.

 

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