[Reproducibility of measuring retinal nerve fiber density. Comparison of optical coherence tomography with the nerve fiber analyzer and the Heidelberg retinal tomography device].
BACKGROUND
Glaucoma is associated with a progressive loss of retinal ganglion cell axons and the evaluation of the thickness of the retinal nerve fibre layer (RNFL) is important for early diagnosis and follow-up. Results of RNFL thickness measurements may vary according to the devices used. Therefore, the present study has analysed and compared the reproducibility of data obtained with three different instruments.


METHODS
RNFL thickness was determined using a circular identification line around the optic nerve head by optical coherence tomography (OCT), a Heidelberg Retina Tomograph (HRT) and a Nerve Fiber Analyser (NFA). Each eye was tested six times. The values for RNFL thickness were calculated for the superior, inferior, nasal and temporal areas. A one-way analysis of variance with random effects was chosen to estimate the variance components. The intraclass correlation coefficient (ICC) as a measure of reliability and the coefficient of variation (CV%) as a measure of precision were determined to estimate the reproducibility of RNFL thickness measurements.


RESULTS
With all three instruments, the reproducibility of measurements between the superior, inferior, temporal and nasal areas did not differ significantly suggesting that reproducibility does not depend on the thickness of the RNFL. Data obtained by NFA showed the highest ICC values (0.9) and lowest CV% values (7.0), followed by those obtained by HRT (reliability ICC 0.8; precision CV% 12). A markedly lower degree of reproducibility was found for the OCT compared to NFA and HRT (reliability ICC 0.5; precision CV% 15).


CONCLUSIONS
The comparison of RNFL thickness measurements with OCT, NFA, and HRT showed that the NFA yielded the most reliable results followed by HRT.
Klemm
M
M
Universitätsaugenklinik Hamburg, Martinistrasse 52, 20246 Hamburg.
Rumberger
E
E
Walter
A
A
Richard
G
G
D000293:Adolescent; D000328:Adult; D000368:Aged; D001369:Axons / Q000000981:diagnostic imaging; D001718:Birefringence; D005260:Female; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal / Q000295:instrumentation*; D008857:Microscopy, Interference / Q000295:instrumentation*; D008859:Microscopy, Polarization / Q000295:instrumentation*; D008875:Middle Aged; D009412:Nerve Fibers / Q000000981:diagnostic imaging*; D012016:Reference Values; D015203:Reproducibility of Results; D012160:Retina / Q000033:anatomy & histology*; D012165:Retinal Ganglion Cells / Q000000981:diagnostic imaging; D014054:Tomography / Q000295:instrumentation*; D014463:Ultrasonography