June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
A method for simultaneous assessment of retinal vascular oxygenation and diameter in response to light flicker in humans
Author Affiliations & Notes
  • Anthony E Felder
    Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL
  • Justin Wanek
    Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL
  • Norman P Blair
    Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL
  • Mahnaz Shahidi
    Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL
  • Footnotes
    Commercial Relationships Anthony Felder, None; Justin Wanek, None; Norman Blair, None; Mahnaz Shahidi, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2015, Vol.56, 4407. doi:
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      Anthony E Felder, Justin Wanek, Norman P Blair, Mahnaz Shahidi; A method for simultaneous assessment of retinal vascular oxygenation and diameter in response to light flicker in humans. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4407.

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

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Abstract
 
Purpose
 

Light flicker stimulation increases neural activity, thereby augmenting retinal oxygen metabolism and blood flow. Alterations in retinal vascular oxygen saturation (SO2) and diameter, and their responses to light flicker may be used to detect abnormalities due to disease. The purpose of the study was to report an optical imaging system for combined measurements of retinal vascular SO2 and diameter before and during light flicker stimulation in humans.

 
Methods
 

A slit lamp biomicroscope was modified for dual wavelength retinal oximetry at 570nm and 606nm. Fundus images were acquired in control subjects (Age: 39±17 years, N=7) and diabetic retinopathy (DR) subjects (Age: 50±13 years, N=7; 3 PDR, 4 NPDR) (P=0.18) before and during light flicker stimulation at 530nm. A customized software algorithm measured arterial and venous diameter (DA and DV) and optical density ratios (ODR). Arterial and venous oxygen saturations (SO2A and SO2V) were obtained from an ODR to SO2 calibration and oxygen extraction fraction (OEF) was calculated as (SO2A- SO2V)/SO2A. Repeatability and inter-subject variability were assessed in control subjects before light flicker stimulation.

 
Results
 

Repeatability of DA, DV, SO2A and SO2V were 2µm, 2µm, 2% and 3%, respectively. Inter-subject variability of DA, DV, SO2A and SO2V were 4µm, 4µm, 4% and 4%, respectively. As expected, DV was significantly larger than DA and SO2A was significantly higher than SO2V (P≤0.03). DA, DV, and SO2V were similar between control and DR subjects (P≥0.20) but SO2A was higher in DR subjects (P≤0.02). In control subjects, DA and DV increased significantly during light flicker stimulation (P<0.05). In DR subjects, DV increased significantly during light flicker (P=0.002) but DA did not (P=0.09). Light flicker stimulation did not significantly alter SO2A, SO2V or OEF in control or diabetic subjects (P≥0.08).

 
Conclusions
 

A retinal imaging system was established for combined quantitative assessment of retinal vascular SO2 and diameter alterations in response to light flicker stimulation. The system detected alterations in retinal vascular oxygenation and caliber due to DR and light flicker stimulation.  

 
Retinal vascular oxygen saturation (SO2) and diameter (D) in control and diabetic retinopathy (DR) subjects before and during light flicker stimulation.
 
Retinal vascular oxygen saturation (SO2) and diameter (D) in control and diabetic retinopathy (DR) subjects before and during light flicker stimulation.

 
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