Abstract
Purpose:
Optic disc evaluation from stereo fundus photographs(SFP) by experienced examiners still remain the worldwide standard of glaucoma assessment both in clinical practice and the mass screening of glaucoma, while optic disc morphologic parameters(ODMP) obtained by SD-OCT are going to be widely used in clinical practice. We correlated ODMP obtained using a newly developed simultaneous stereo fundus camera system (Nonmyd WX, Kowa Co. Ltd., Japan:WX) to those obtained using a SD-OCT instrument widely used (Cirrus, Carl Zeiss Meditec, Dublin, CA:Cirrus).
Methods:
The study included 29 eyes of 15 glaucoma patients (Age= 68.4 ± 9.4 yrs, MD= -8.6±4.6dB) who underwent imaging of the optic disc using WX and Cirrus at intervals within 1 month. In WX system, an experienced investigator determined the disc and cup contours viewed using a stereo glass and vertical cup/disc (V-C/D) ratio, disc area (DA) and rim area(RA), and cup volume(CV) were calculated using with 3-dimensional analysis software (VK-2 WX, Kowa) where correction for magnification was done using Gullstrand schematic eye (Optic disc parameters1: ODP1) or by entering refraction and corneal curvature of each eye (ODP2). V-C/D, DA and RA and CV by Cirrus were obtained using ONH analysis.
Results:
V-C/D, DA ,RA , CV obtained using ODP1 protocol were 0.82 ± 0.06, 2.32 ± 0.48 mm2, 0.83 ± 0.23 mm2 and 0.35 ± 0.18 mm3, and those obtained using ODP2 protocol 0.82 ± 0.06, 2.48± 0.53 mm2, 0.83 ± 0.27 mm2 and 0.40 ± 0.21 mm3, and corresponding figures obtained using Cirrus were 0.79 ± 0.09, 1.89 ± 0.40 mm2, 0.70 ± 0.21mm2 and 0.50 ± 0.33 mm3, respectively. V-C/D, DA and RA obtained using WX were greater (P= 0.000 ~0.044, paired t-test), but CV smaller (P=0.000) than those with Cirrus. Spearman’s correlation coefficients between ODP1 and Cirrus results were 0.497, 0.793, 0.631, 0.838 (P<0.005) for V-C/D, DA,RA and CV, and those between ODP2 and Cirrus results were 0.497, 0.899, 0.713, 0.845 (P<0.005). Correlation of Cirrus results to ODP2 was higher than that to ODP1 for DA (P=0.047).
Conclusions:
ODMP values obtained with Nonmyd WX were well correlated to those with Cirrus and correction for magnification by entering refraction and corneal curvature of each eye improved correlation. V-C/D, DA, RA with the former system were 3.6%, 18.5%, 15.3% greater and CV 43.6% smaller than those with Cirrus.