COMPARISON BETWEEN TOMOGRAPHIC SCANNING EVALUATION AND PHOTOGRAPHIC MEASUREMENT OF THE NEURORETINAL RIM

PURPOSE: To compare laser tomographic scanning evaluation with photogr aphic measurement of size and shape of the neuroretinal rim. METHODS: For 25 normal eyes and 32 glaucomatous eyes, the optic disks were exam ined with the Heidelberg Retina Tomograph (software version 1.11) for confocal laser tomographic scanning evaluation, and color stereoscopic optic disk photographs for planimetric measurements, Area and width o f the neuroretinal rim were determined as percentages of the disk area and diameter, respectively. RESULTS: For the normal and glaucomatous eyes, the tomographic results compared with the photographic measureme nts disclosed significantly larger values for the relative width and r elative area of the neuroretinal rim, The differences between both met hods were most marked in the nasal part of the optic disk and least ma rked in the temporal disk region, The relative differences increased s ignificantly (P <.05) with increasing degree of glaucomatous optic ner ve damage. CONCLUSIONS: In normal and glaucomatous eyes, the Heidelber g Retina Tomograph determines the neuroretinal rim, expressed as perce ntage of optic disk measurements, to be significantly larger than when the rim is evaluated on optic disk photographs, Because parts of the central retinal vessel trunk are defined as neuroretinal rim in the al gorithm of the Heidelberg Retina Tomograph, the differences between He idelberg Retina Tomograph measurements and photographic determinations of the rim are largest in the nasal disk region and smallest in the t emporal disk area, The neuroretinal rim shape and neuroretinal rim are a differ appreciably between the two methods, These differences increa se with increasing degree of glaucomatous optic nerve damage.