Reproducibility of topometric data acquisition in normal and glaucomatous optic nerve heads with the laser tomographic scanner

Abstract

The reproducibility of optic disc cup measurements was analyzed in 24 eyes of 24 patients [8 normals, 8 glaucoma patients, 8 glaucoma suspects] using the Laser Tomographic Scanner. The mean coefficient of variation in triple measurements was 5.0% for the cup area, 5.4% for the rim area, 7.0% for the cup volume, 4.0% for the mean cup depth, and 4.3% for the maximum cup depth. Mean reliability between two of the three measurements performed in each eye was better than 0.988 for the cup area, 0.995 for the cup volume and 0.996 for the mean cup depth readings. These results suggest that laser scanning tomography allows highly reproducible measurements in living eyes and adds an important tool to the ophthalmologist's armamentarium for the diagnosis and follow-up of glaucoma patients.

First-line therapy with latanoprost 0.005% results in improved ocular circulation in newly diagnosed primary open-angle glaucoma patients: a prospective, 6-month, open-label study

“…The method used by this device has been described in detail. [38][39][40][41][42][43][44] In eligible eyes, after keratometric values were measured, one topographic image was obtained through a dilated pupil (by using tropicamide 1%, Alcon, Fort Worth, Texas, USA). This is in contrast to the standard protocol of 3 images recommended usually.…”

Detection of glaucomatous optic nerve head by using Heidelberg topographic maps

“…Even if each image is made by many points, users prefer to employ standard parameters for each system and do not use all the available data. [13][14][15][16][17][18][19][20][21][22] To obtain parameter measurements, an outline had to be drawn around the outer optic disc edge and although this technique had a good reproducibility, the contour line position could change from one center to another. 10 The anatomical variability of normal ONH shape makes it difficult to differentiate normal from glaucomatous optic discs.…”

“…The accuracy and reproducibility of this instrument have previously been described in detail. [13][14][15][16][17][18][19][20][21][22] The HRT uses a scanning confocal laser imaging system, which produces a series of 32 confocal images of the back of the eye at consecutive focal planes, each 256 Â 256 pixels. This series is converted by further processing into a single 3-D topographic image.…”

The effectiveness of the Heidelberg Retina Tomograph and laser diagnostic glaucoma scanning system (GDx) in detecting and monitoring glaucoma

“…However, the literature is unequivocal that variability is higher in glaucomatous than normal eyes. [77][78][79] The issue of repeatability must be considered within the context of diagnostic precision (Chapter 7). Bailey and colleagues 242 highlighted the issue that, if concordance between examinations is high, it may indicate that the scale of measurements is too coarse, which would reduce diagnostic precision.…”

“…78 Their findings corroborate those of other researchers that measurement variability is greater in glaucoma patients than normal individuals. [77][78][79] Other sources of increased variability in HRT measurements are accommodation, 80 incorrect alignment of the laser beam with the optic disc 81,82 and variations in the location of the reference plane. 83 …”