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R.A. Bilonick, Z. Burgansky–Eliash, G. Wollstein, H. Ishikawa, L. Kagemann, R.J. Noecker, J.S. Schuman; Heidelberg Retina Tomograph (HRT) II vs. HRT 3: What Is the Difference? . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3633.
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© ARVO (1962-2015); The Authors (2016-present)
The newly released Heidelberg Retina Tomograph (HRT 3) software uses a larger normative database than the HRT II software for classification of measured parameters. The software also provides stereometric disc measurements without the need of subjectively defining the disc margin. A neural network technique (Glaucoma probability score, GPS) is applied to these measurements for classification. In this study we analyzed a single dataset of HRT images, comparing the results of 3 software applications (1) HRT II, (2) HRT 3 with the disc margin imported from the HRT II analysis, and (3) the HRT 3 with GPS automated disc margin identification.
527 eyes of 284 consecutive subjects (glaucoma patients, glaucoma suspects, and healthy subjects) evaluated in a glaucoma clinic were recruited for the study. The global stereometric parameters from HRT II and HRT 3 were compared using a repeated measures model. The cup area was compared to GPS cup size using a linear mixed–effects model. The agreement (Kappa) between HRT II and 3 Moorfields regression analysis (MRA) and HRT 3 GPS classification methods was calculated.
Global stereometric parameters were statistically smaller in HRT 3 than the corresponding HRT II measurements. GPS cup size was lower than both the HRT II and HRT 3 cup area by an average 0.27 and 0.24 mm2 respectively (both p<0.0001). The kappa for agreement between classifications (within normal limits (WNL), borderline (BL) and outside normal limits (ONL)) of MRA by HRT 3 and HRT II was 0.58, between GPS and MRA by HRT II was 0.42, and between GPS and HRT 3 MRA was 0.44. Twenty–nine percent (29%) of participants labeled as WNL by HRT II MRA were classified as BL by HRT3 MRA, and 37% of subjects classified as BL by HRT II MRA were classified as ONL by HRT3 MRA.
HRT 3 provided smaller stereometric disc measurements than HRT II. GPS cup area was smaller compared to the measurement in HRT II or HRT 3 analysis which requires a user–defined disc contour line. A moderate degree of agreement was found between the MRA of HRT 3 and HRT II, with lower agreement between the classification of GPS and MRA of either HRT 3 or HRT II.
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