Abstract

P 160

Agreement among three optical imaging methods for the assessment of optic disc topography

Hoffmann E. M.^1,2, Bowd C.¹, Medeiros F. A.¹, Boden C.¹, Grus F. H.², Zangwill L. M.¹, Weinreb R. N.¹, Pfeiffer N.^2
1Hamilton Glaucoma Center, Department of Ophthalmology, University of California of San Diego, La Jolla, USA; ²Department of Ophthalmology, University of Mainz, Mainz, Germany

Objective: To assess the agreement of disc topography measurements between Heidelberg Retina Tomograph (HRT II), Retinal Thickness Analyzer (RTA), and the Optical Coherence Tomograph (Stratus OCT).
Methods: Forty-two randomly chosen eyes of 42 subjects were included. Each subject underwent HRT II, RTA, and Stratus OCT examination. Two experienced examiners drew the contour lines for HRT and RTA. Bland and Altman plots were used to evaluate agreement for each topographic parameter among the instruments. Spearman’s coefficient of rank correlation was evaluated for each topographic parameter.
Results: For optic disc area, the agreement between HRT II – RTA and Stratus OCT – RTA revealed the existence of proportional bias, indicated by significant slopes of the regression lines (P=0.01 and P=0.02, respectively). The 95% limits of agreement between instruments varied with the actual optic disc size measurement. HRT II disc area measurements tended to be consistently lower than Stratus OCT disc area measurements (Fixed bias). Spearman’s correlation coefficient between the instruments ranged from r=0.35 (Rim Area, HRT – Stratus OCT) to r=0.91 (Cup Area, HRT – RTA).
Conclusions: Moderate to high correlation was found in measurements of optic disc topography among different instruments. However, the analysis of agreement indicated important discrepancies among instruments. Therefore, these instruments should not be used interchangeably to obtain measurements of the optic disc for glaucoma diagnosis.

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