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T. G. Zeyen, S. Fieuws, I. Stalmans, C. Breusegem; The Influence of the Variability of the Standard Reference Height on Stereometric Parameters With the Heidelberg Retina Tomograph II. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3649. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the variability of the standard reference height (RH) in consecutive examinations with the Heidelberg Retina Tomograph II (HRT II). To evaluate the influence of RH variability on 2 stereometric parameters, rim area (RA) and retinal nerve fiber layer (RNFL).
Retrospective review of HRT II results of all the patients examined in the glaucoma department from August to October 2007. Patients with a minimum of 3 consecutive HRT's labeled as acceptable or better were included. Only one eye per patient was selected for analysis (right eye). The left eye was chosen if the right eye had < 3 consecutive examinations or a poor quality control score. A difference of 10% in standard RH compared to baseline was considered as excess variability.
641 patients were examined. 150 patients (150 eyes) met the inclusion criteria resulting in a total of 553 examinations for analysis of which 403 were follow-up examinations. The mean total number of HRT's per patient was 3.7 (minimum 3, maximum 7). The average intra-individual excess variability of the RH was 45.8%. The median (absolute) difference in RH compared to baseline in all examinations was 8.6% (IQR:3.9%-16.2%). 55.3% and 75.1% of the fluctuations in RA and RNFL respectively, could be attributed to fluctuations in RH.
There is considerable variability in the standard reference height of consecutive examinations of the same eye. These findings indicate that changes of stereometric parameters should be taken with caution when the variability of the standard reference height exceeds 10% compared to baseline.
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