Semi‐automated retinal vessel analysis in nonmydriatic fundus photography

Abstract

ABSTRACT.Purpose: Funduscopic assessment of the retinal vessels may be used to assess the health status of microcirculation and as a component in the evaluation of cardiovascular risk factors. Typically, the evaluation is restricted to morphological appreciation without strict quantification. Our purpose was to develop and validate a software tool for semi-automated quantitative analysis of retinal vasculature in nonmydriatic fundus photography. Methods: MATLAB software was used to develop a semi-automated image recognition and analysis tool for the determination of the arterial-venous (A/V) ratio in the central vessel equivalent on 45°digital fundus photographs. Validity and reproducibility of the results were ascertained using nonmydriatic photographs of 50 eyes from 25 subjects recorded from a 3DOCT device (Topcon Corp.). Two hundred and thirty-three eyes of 121 healthy subjects were evaluated to define normative values. Results: A software tool was developed using image thresholds for vessel recognition and vessel width calculation in a semi-automated three-step procedure: vessel recognition on the photograph and artery/vein designation, width measurement and calculation of central retinal vessel equivalents. Mean vessel recognition rate was 78%, vessel class designation rate 75% and reproducibility between 0.78 and 0.91. Mean A/V ratio was 0.84. Application on a healthy norm cohort showed high congruence with prior published manual methods. Processing time per image was one minute. Conclusions: Quantitative geometrical assessment of the retinal vasculature may be performed in a semi-automated manner using dedicated software tools. Yielding reproducible numerical data within a short time leap, this may contribute additional value to mere morphological estimates in the clinical evaluation of fundus photographs.

Total Retinal Blood Flow in a Nonhuman Primate Optic Nerve Transection Model Using Dual-Beam Bidirectional Doppler FD-OCT and Microsphere Method

“…This was done as described previously. 40,41 Arteriovenous ratio was calculated as CRAE/CRVE. It describes the ratio of retinal arteries to retinal veins, a parameter frequently used to describe changes in vessel calibers in the course of diseases.…”

Optical coherence tomography‐based retinal vessel analysis for the evaluation of hypertensive vasculopathy

“…As early as 1974, Parr and Spear proposed the central retinal equivalent for arteries (Parr & Spears 1974a,b) that was extended to retinal veins by Hubbard et al in 1999(Hubbard et al 1999. Later on, several computer-based measurements were programmed and evaluated in epidemiological as well as in clinical and experimental studies (Wong et al 2004;Benavent et al 2009;Cheung et al 2010;Garcia-Ortiz et al 2012;Papadopoulou et al 2012;Pemp et al 2013;Schuster et al 2013).…”

“…In contrast to these devices that determine dynamic blood flow parameters, our method evaluates a static situation of the retinal vasculature, providing quantitative analysis of peripapillary retinal vessels diameter. There are several methods evaluating retinal vessel width along a vessel on fundus photos; (Knudtson et al 2003;Schuster et al 2013) peripapillary OCT scans do not allow to analyse vessel over a course yet. Hence, the analysis of a single section might be less reliable than a vessel measurement over its course since arterial profile changes along the vessel.…”

“…Validation of this algorithm was performed on high-quality scan of 20 eyes of 20 test subjects, fully masked for all contingent data to the operators with regard to the following parameters: intrarater variability and inter-rater variability between two independent operators. Fundus photographic evaluation of retinal vasculature was performed with a validated semi-automated software algorithm (Schuster et al 2013), and the OCT-based vessel parameter was compared to central retinal vessel equivalents and its A/V ratio. Resulting data were statistically analysed using SPSS software (SPSS 19.0; SPSS Chicago, IL, USA).…”

Associations of cardiovascular risk factors and retinal vessel dimensions at present and their evolution over time in a healthy working population

“…For the assessment of retinal vessel diameters, validated semi‐automated software (Schuster et al. ) was used, calculating the central retinal arterial equivalent ( CRAE ), the central retinal venular equivalent ( CRVE ) and the arterious–venous ratio. This software has been validated and is able to use even smaller vessels for the analysis, and the analysis of a picture is performed within few minutes (Schuster et al.…”