Optic disc biomorphometry with the Heidelberg Retina Tomograph at different reference levels

Abstract

ABSTRACT.Purpose: The Heidelberg Retina Tomograph (HRT) is a confocal scanning laser tomograph that produces high resolution optical section images of the optic disc and central retina. Measurement accuracy and reproducibility is good. Several of the stereometric variables depend on the definition of a reference plane level. The purpose of the present study was to evaluate the four different reference levels in terms of their advantages and disadvantages in clinical work. Methods: Sixty-seven randomly chosen eyes belonging to 67 subjects were included in this study. Forty of the eyes were healthy and 27 had glaucoma. The HRT with software versions 1.09 and 1.11 was used to acquire and evaluate topographic measurements of the optic disc. Image analysis was performed at four different reference levels: 320 mm fixed offset reference level (REFd) (version 1.09), an individually determined reference level (REFi), a papillo-macular reference level (REFm) and a flexible reference level (REFf) (version 1.11). ANOVA was used to determine differences in the topographic parameters between the reference levels. Key words: confocal scanning laser tomograph ª Heidelberg Retina Tomograph (HRT) ª RNFL thickness ª rim area ª rim volume ª reference level ª optic disc ª glaucoma.

Heidelberg retina tomograph parameters of the optic disc in eyes with progressive retinal nerve fibre layer defects

“…1997). It is independent of the reference plane, and thus unaffected by any variability to which the reference plane may be subject (Vihanninjoki et al. 2002; Tan & Hitchings 2003).…”

“…It represents the overall shape of the ONH and has been shown to have a significant correlation with glaucomatous damage in several studies (Uchida et al 1996;Teesalu et al 1997). It is independent of the reference plane, and thus unaffected by any variability to which the reference plane may be subject (Vihanninjoki et al 2002;Tan & Hitchings 2003).…”

Retinal nerve fibre layer cross‐sectional area, neuroretinal rim area and body mass index

“…After obtaining the image, the optic disc border was manually outlined with the conventional optic disc photograph available to help in case of doubt to determine the optic disc margin. The technique has already been described in detail (Vihanninjoki et al 2002;Resch et al 2011). We measured the area of the optic disc and neuroretinal rim and the RNFL cross-sectional area.…”

Evaluation of optic nerve head configuration in various types of optic neuropathy with Heidelberg Retina Tomograph

“…All the participants underwent imaging analyses with HRT (software version 3.04, Heidelberg Engineering GmbH, Heidelberg, Germany) essentially according to the technique described previously. [1][2][3][4][5][6] In brief, for each HRT imaging session three 15 Â 15 degree images were obtained for each eye by one of the authors (ANK). After generating a mean topographic image, disc margin was delineated as a contour line by the same observer referring to an optic disc photograph.…”

“…HRT automatically determines the reference plane 50 mm below the mean retinal surface at the temporal sector of the contour line between 350 and 356 degree, which is located on the papillomacular bundle, because RNFL thickness of this location is assumed to be 50 mm without considerable individual variation. 5,6 Cup area is defined as the area beneath this reference plane. In glaucoma, RNFL thickness of this specific location is supposed to be preserved until the advanced stage.…”