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Makoto Araie, Aiko Iwase, Ryo Kawasaki, Jun Suehiro, Akihiko Sekine; An improved semi-automatic method to measure retinal vessel caliber from fundus photographs and measurement results in normal Japanese. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3321.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal vessel caliber (RVC) changes are associated with various systemic and ocular abnormalities. Accurate magnification correction in each eye is indispensable for measuring RVC from fundus photographs, but currently available semi-automatic methods to determine RVD are not necessarily satisfactory in this respect.
In addition to Littmann's correction, ray-tracing algorithm was applied to optical system of Topcon non-mydriatic fundus camera (TRC-NW7, Topcon, Tokyo) and magnification was corrected using corneal curvature, axial length (AL) and refraction of each subject eye. RVC was always determined in an annular area between 1.8 and 2.7 mm from the disc center. Measurement reproducibility was checked in 20 normal eyes by 4 independent examiners, and the results with the current method were compared to those with Interactive Vessel Analysis System (IVAN) in other 180 normal eyes of 99 subjects with mean age of 52 yrs. Factors relating to central retinal arteriolar equivalent (CRAE) were studied in 793 right eyes with AL less than 26 mm of 793 normal Kumejima Study participants with average age of 50 yrs. The Ethic Committee of Kumejima Town approved the study.
Intra-individual ICC was 0.921-0.993 and 0.995-0.999, and Inter-individual ICC 0.998 and 0.996 for CRAE and central retinal venular equivalent (CRVE), respectively. The current method yielded CRAE and CRVE values 1.8 % smaller and .4.3% greater than those with IVAN (P<0.017), and the difference between the results with the two methods was AL-dependent. In normal Japanes, CRAE was 162.5 +/- 9.3 (SD) and CRVE 232.9 +/- 16.1 um. A multiple regression analysis revealed that female gender (P=0.002), older age (P=0.000), higher blood pressure (P=0.014), longer AL (P=0.000) and larger beta-peripapillary atrophy (beta-PPA) (P=0.000) were correlated with CRAE in this population.
An improved method to measure RVC from fundus photographs with reasonable measurement reproducibility was developed. In normal Japanese, two ocular factors, axial length and beta-PPA area, were newly found to significantly correlate with CRAE beside systemic factors well known to affect it.
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