Intraobserver and interobserver reproducibility in the evaluation of optic disc stereometric parameters by Heidelberg retina tomograph

doi:10.1016/S0161-6420(02)01032-1

Ophthalmology

Volume 109, Issue 6, June 2002, Pages 1072-1077

Presented in part at the annual meeting of the Association for Research in Vision and Ophthalmology (ARVO), Ft. Lauderdale, Florida, May 2001.

https://doi.org/10.1016/S0161-6420(02)01032-1 Get rights and content

Abstract

Purpose: To assess intraobserver and interobserver reproducibility of the measurement of stereometric parameters of the optic disc by means of the Heidelberg Retina Tomograph I (HRT).

Study design: Observational study, with interobserver variability.

Participants: Fifty-five volunteers (healthy subjects and patients with glaucoma).

Methods: HRT examination of the optic disc was repeated on 3 consecutive days on 1 eye of each of the 55 subjects. During each session, five single images were randomly acquired by two independent observers. One mean topography image (MTI), based on three single images, was then built at each session. For the intraobserver intraimage evaluation, the two observers traced their own contour line on one randomly chosen MTI. This procedure was repeated three times. For the intraobserver interimage and interobserver intra/interimage evaluations, the two observers traced their own contour line on the MTI of the first session, which was then automatically superimposed on the MTIs of the other two sessions.

Main outcome measures: Reproducibility of the 12 stereometric parameters was calculated for each observer by means of the intraclass correlation coefficient (ICC). The expected range of variability between two independent evaluations was calculated by the scatter-plots of each test—retest difference versus their mean. The standard deviation of the mean test—retest score differences was used to describe the spread of score differences.

Results: The ICC ranged between 0.79 and 0.99 for intraobserver intraimage and between 0.56 and 1 for intraobserver interimage evaluation. The ICC ranged between 0.54 and 0.99 for interobserver intraimage and between 0.65 and 0.97 for the interobserver interimage evaluation. ICC was almost perfect to perfect for planimetric measures (0.81 < ICC ≤ 1), substantial to almost perfect for volumetric and cup measures (0.61 < ICC ≤ 0.99), and moderate to almost perfect for retinal nerve fiber layer related measures (0.41 < ICC < 0.99). The expected variability was low (95% confidence interval, <±9%). Interimage evaluation showed a higher variability than intraimage evaluation in both of interobserver (P = 0.012) and intraobserver evaluation (P = 0.028 and P = 0.031 for the two observers).

Conclusions: Measurement of optic disc stereometric parameters by HRT is highly reproducible. However, the use of retinal nerve fiber layer-related parameters should be taken cautiously. The image acquisition-induced variability seems larger than the operator-induced variability.

Section snippets

Material and methods

The study population consisted of 55 volunteers aged between 25 and 79 years attending the Outpatient Service at the S. Paolo Hospital. The protocol of the study was approved by the local ethical review committee. After informed consent was obtained, one eye was randomly chosen for each subject. The sample included 11 eyes affected by primary open angle glaucoma at different stages and eyes with a wide range of disc, rim, and cup sizes and different morphologic characteristics. The glaucomatous

Results

The study is based on a total of 165 MTIs, whose mean standard deviation was 27.87 ± 10.56 (range, 11.51–66.03).

The descriptive statistics values of the 12 parameters for each observer are summarized in Table 1; there was no statistically significant difference between the two observers for any of the parameters.

Discussion

Primary open-angle glaucoma patients are affected by optic nerve head modifications and retinal nerve fiber loss, as well as by progressive visual field alterations. To plan a therapy designed to preserve visual function for as long as possible, it seems clinically appropriate to use instruments capable of detecting progressive structural changes.

An important step in the follow-up of a chronic disease is to know whether the observed changes are related to test variability or to real disease

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^☆: Funded by a grant from the Ministero dell’Universita’ e della Ricerca Scientifica, Italy.

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Intraobserver and interobserver reproducibility in the evaluation of optic disc stereometric parameters by Heidelberg retina tomograph☆

Abstract

Section snippets

Material and methods

Results

Discussion

Ophthalmology

Am J Ophthalmol

Ophthalmology

Am J Ophthalmol

Am J Ophthalmol

Am J Ophthalmol

Development of glaucomatous changes of the optic nerve

Histopathologic validation of Fourier-ellipsometry measurements of retinal nerve fiber layer thickness

Arch Ophthalmol

Quantification of nerve fiber layer thickness in normal and glaucomatous eyes using optical coherence tomography

Arch Ophthalmol

A new method for rapid mapping of retinal thickness at the posterior pole

Invest Ophthalmol Vis Sci

Reproducibility of topographic parameters obtained with the Heidelberg Retina Tomograph

J Glaucoma