Papillenausmessung mit Planimetrie und „Optic Nerve Head Analyzer” bei Glaukom und Glaukomverdacht - Teil 1: Vergleich der beiden Meßmethoden

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Abstract
Two-dimensional planimetric measurement of the neuroretinal rim using the method described by Betz has proved to be one of the most objective parameters in evaluating the optic nerve head. Using a three-dimensional stereoscopic measuring procedure (ONHA) described by Cornsweet, the volume of the papillary excavation can be quantified. The two methods were compared in a study involving 67 eyes with confirmed and suspected glaucoma. In agreement with published data, the correlation between the two measuring procedures was good as regards the disk surface (r2 = 0.73), the surface of the excavation (r2 = 0.90), and the cup/disk ratio (r2 = 0.63), although the last-mentioned parameter is calculated differently. While the disk surface as measured by planimetry was significantly greater than with ONHA, the cup surface measurements were almost exactly the same. In contrast to the results of other authors, the measurements of the neuroretinal rim surface correlated poorly (r2 = 0.09). The difference between the two methods in measuring the rim surfaces depends to a great extent on their absolute size and on the cup surface. The different procedures for defining the boundary of the excavation (in planimetry horizontal boundary definition, with the ONHA 150 micrometers below the retinal surface) are considered responsible for this. Advantages and drawbacks of these two clinical measuring methods are discussed. Once the currently excessive variability in the measurements has been reduced, measurement of the excavation volume could prove to be an important parameter for assessing the development of the optic nerve head in confirmed or suspected glaucoma cases.

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