Improving the repeatability of Heidelberg retina tomograph and Heidelberg retina tomograph II rim area measurements

Abstract

Aims: To devise and test strategies for improving Heidelberg retina tomograph (HRT and HRT-II) rim area (RA) repeatability and assess the benefit of the strategies in time series of HRT images. Methods: The effect of the standard and 320 mm reference planes and image quality on RA repeatability was assessed in a test-retest HRT image dataset from 74 subjects. A longitudinal HRT image dataset from 30 ocular hypertensive subjects was analysed by linear regression of RA over time, with each of the reference planes and using a manual image alignment facility. RA variability was estimated by comparing the standard deviation of residuals (RSD) generated by each linear regression. Results: RA repeatability was better with the 320 mm reference plane (repeatability coefficient 0.17 mm 2 ), improving further with only good quality images (repeatability coefficient 0.08 mm 2 ). For the longitudinal data, a significant (p,0.0001) reduction in the RSD from 0.10 to 0.05 mm 2 was obtained with the 320 mm reference plane. Manual alignment led to a further significant (p,0.0001) reduction in the RSD to 0.04 mm 2 . Conclusions: The findings support the use of a 320 mm reference plane and manual image alignment to analyse RA over time. The estimates of RA repeatability may be used to define thresholds for glaucomatous change.

Optical Coherence Tomography of the Swollen Optic Nerve Head: Deformation of the Peripapillary Retinal Pigment Epithelium Layer in Papilledema

“…22,[37][38][39][40][41] While this may be correct in a slowly progressive condition like glaucoma, our findings in papilledema shows substantial deformations of the peripapillary RPE/BM, in some cases over short time intervals, relative to other surface and subsurface regions of the optic disc. There may be limits to the use of the RPE/BM as a reference plane in patients with intracranial hypertension.…”

Optic Disc and Visual Field Progression in Ocular Hypertensive Subjects: Detection Rates, Specificity, and Agreement

“…A manual alignment facility was used to correct contour line position if the automatically placed contour line was misplaced or if there was a magnification change. 17 When a satisfactory contour line position could not be achieved, the mean topography was excluded from the analysis. Eight mean topographies were excluded from the analysis, as a result either of a double image being present or if the image was so grainy as to preclude visualization of Elschnig's ring.…”

The Use of HRT With and Without the Aid of Disc Photographs

“…The use of disc photographs in plotting the contours has been used selectively in studies, and other studies have not used them in defining the contours. [11][12][13] Furthermore, there is little literature that directly compares the results on whether it is truly beneficial. Spencer et al 14 showed that HRT measurements for the vertical optic disc diameter were significantly smaller compared with the measurements taken on optic disc photographs.…”