Comparison of long-term fluctuations: laser scanning tomography versus automated perimetry.
BACKGROUND
The aim of our study was to investigate the long-term variability of laser scanning tomography and to compare it with the long-term variability of automated perimetry.


METHOD
We retrospectively reviewed the charts of 199 patients (394 eyes) who underwent both automated perimetry (Octopus) and laser scanning tomography (Heidelberg retina tomograph, HRT) in our hospital since 1994. All patients either had ocular hypertension (OHT) or early stage glaucoma. The mean follow-up time was 5.4 years; the average number of examinations was 7.7. The variability was described by the variance ratio VR.


RESULTS
The HRT parameters showed very similar long-term fluctuations as the Octopus parameters. In detail: VR of HRT parameters ranged from 0.04 (cup area, cup volume, mean cup depth) to 0.35 (contour height variation), whereas VR of Octopus parameters ranged from 0.12 (mean sensitivity) to 0.15 (loss variance).


CONCLUSIONS
The long-term variability of HRT parameters is in the same range as the long-term variability of visual field parameters. Since it is now widely accepted that visual field changes over time should be reproduced at least once or twice before clinical consequences can be drawn, the same should be postulated for HRT changes over time.