June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
Evaluation of Optic Disc Perfusion in Normal-Tension Glaucoma Patients by Optical Coherence Tomography Angiography
Author Affiliations & Notes
  • Dagny Zhu
    Ophthalmology, University of Southern California, Los Angeles, CA
  • Alena Reznik
    Ophthalmology, University of Southern California, Los Angeles, CA
  • Chieh-Li Chen
    University of Washington, Seattle, WA
  • Ruikang K Wang
    University of Washington, Seattle, WA
  • Carmen A Puliafito
    Ophthalmology, University of Southern California, Los Angeles, CA
  • Footnotes
    Commercial Relationships Dagny Zhu, Carl Zeiss Meditech (F); Alena Reznik, Carl Zeiss Meditech (F); Chieh-Li Chen, Carl Zeiss Meditech (F); Ruikang Wang, Carl Zeiss Meditech (F), Carl Zeiss Meditech (P); Carmen Puliafito, Carl Zeiss Meditech (F)
  • Footnotes
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Investigative Ophthalmology & Visual Science June 2015, Vol.56, 2745. doi:
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      Dagny Zhu, Alena Reznik, Chieh-Li Chen, Ruikang K Wang, Carmen A Puliafito; Evaluation of Optic Disc Perfusion in Normal-Tension Glaucoma Patients by Optical Coherence Tomography Angiography. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2745.

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

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Abstract
 
Purpose
 

To evaluate optic disc perfusion in normal-tension glaucoma (NTG) patients using optical coherence tomography (OCT) angiography.

 
Methods
 

Seven eyes of 4 patients with NTG were scanned with a high-speed 1060-nm wavelength swept-source OCT angiography prototype system. A proprietary phase compensation algorithm was used to construct a three-dimensional model of blood flow in the optic disc. The disc flow index, a dimensionless parameter from 0-1 measuring vessel area, density, and flow velocity, was calculated for each optic disc. Stereo photography was used to quantify the cup-to-disc ratio for each optic disc. Humphrey visual field (HVF) deficits and retinal nerve fiber layer (RNFL) thickness were analyzed and correlated with disc flow index using the spearman correlation coefficient.

 
Results
 

The optic discs of NTG patients analyzed spanned a wide range of clinical severity, with cup-to-disc ratios ranging from 0.65 to 0.85 (mean 0.78±0.08) and mean deviation (MD) from -16 to 0.51 (mean -6.7±5.8) and pattern standard deviation (PSD) from 1.6 to 15.5 (mean 7.2±5.2) on HVF. The average disc flow index was 0.26±0.04. Qualitatively, discs with early or moderate glaucomatous optic nerve damage demonstrated a denser microvascular network spanning each level of the retina, choroid, and lamina cribosa compared to more advanced cases. Disc flow index correlated strongly with cup-to-disc ratio (R² = 0.67), suggesting poorer perfusion in discs with larger cups and more severe damage. No such correlation was seen with other measured factors including MD, PSD, and RFNL thickness. Interestingly, the sectoral disc flow index calculated for each quadrant (inferior, superior, nasal, temporal) did not correlate with the structural location of nerve head damage and/or corresponding HVF deficits seen, suggesting a possible compensatory redistribution of blood flow.

 
Conclusions
 

OCT angiography provides a non-invasive method for quantifying disc perfusion in patients with glaucoma. Our results provide additional insights into the pathologic role of altered perfusion in NTG for this unique subset of patients with relatively “normal” intraocular pressures. Clinical treatments for improving disc perfusion in glaucoma patients warrant further investigation.  

 
OCT angiogram of a disc with advanced normal-tension glaucoma. Disc margin is outlined by red line. Note darker areas of microvascular dropout
 
OCT angiogram of a disc with advanced normal-tension glaucoma. Disc margin is outlined by red line. Note darker areas of microvascular dropout

 
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