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Assessment of potential vessel segmentation pitfalls in the analysis of blood flow velocity using the Retinal Function Imager

  • Retinal Disorders
  • Published:
Graefe's Archive for Clinical and Experimental Ophthalmology Aims and scope Submit manuscript

Abstract

Purpose

The purpose of our study was to investigate the potential pitfalls associated with different vessel segmentation methods using the built-in software of the Retinal Function Imager (RFI) for the analysis of retinal blood flow velocity (BFV).

Methods

Ten eyes of nine healthy subjects were enrolled in the study. Retinal blood flow measurements were obtained with the RFI device with a 20° field of view imaging. The same grader segmented the retinal vasculature using the RFI software in both sessions, with segments ranging in length from 50 to 100 pixels (“short segments”) and 100–200 pixels (“long segments”). The blood flow velocities for the arteriolar and venular system were calculated, and the percentage of excluded vessel segments with high coefficients of variation (>45 %) was recorded and compared by paired t test. Spearman's correlation was used to analyze the relationship between measurements by the two vessel segmentation methods.

Results

The number of analyzed vessel segments did not differ significantly between the two groups (28.6 ± 2.6 short and 26.7 ± 4.6 long segments), while the percentage of acceptable segments was significantly higher in the long segment group (65.2 ± 11.4 % vs 85.2 ± 5.87 %, p = 0.001). In the short segment group, more than 15 % of vessel segments were rejected in all subjects, while in the long segment group only three subjects had a rejection rate of greater than 15 % (16.7 %, 18.7 % and 28 %). Both arteriolar and venular velocities were lower in the short segment group, although it reached significance only for arteriolar velocities (3.93 ± 0.55 vs. 4.45 ± 0.76 mm/s, p = 0.036 and 2.95 ± 0.56 vs. 3.17 ± 0.84 mm/s, p = 0.201 for arterioles and venules, respectively). Only venular velocities showed significant correlation (p = 0.003, R 2 = 0.67) between the two groups.

Conclusions

Our results suggest that BFV measurements by the RFI may be affected by segment length, and care should therefore be taken in choosing vessel segment lengths used during the analysis of RFI data. Long segments of 100–200 pixels (400–800 μm) seem to provide more robust measurements, which can be explained by the analysis methodology of the RFI device.

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Acknowledgments

Funding

This study was supported in part by the research grants NIH R01EY020607, NIH Center Grant P30 EY014801 and a grant from Research to Prevent Blindness (RPB), by a research fellowship of the Helen Keller Foundation for Research and Education, and by the Eötvös Scholarship of the Hungarian Scholarship Fund.

Conflict of interest

All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements) or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study.

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Authors and Affiliations

  1. Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA

    Gábor Márk Somfai, Jing Tian & Delia Cabrera DeBuc

  2. Department of Ophthalmology, Semmelweis University, Faculty of Medicine, Budapest, Hungary

    Gábor Márk Somfai

Authors
  1. Gábor Márk Somfai
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  2. Jing Tian
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  3. Delia Cabrera DeBuc
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Correspondence to Delia Cabrera DeBuc.

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Somfai, G.M., Tian, J. & DeBuc, D.C. Assessment of potential vessel segmentation pitfalls in the analysis of blood flow velocity using the Retinal Function Imager. Graefes Arch Clin Exp Ophthalmol 254, 1075–1081 (2016). https://doi.org/10.1007/s00417-015-3166-0

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  • DOI: https://doi.org/10.1007/s00417-015-3166-0

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