Agreement among spectral-domain optical coherence tomography instruments for assessing retinal nerve fiber layer thickness.
OBJECTIVE
To assess the agreement of parapapillary retinal nerve fiber layer (RNFL) thickness measurements among 3 spectral-domain optical coherence tomography (SD-OCT) instruments.


METHODS
Observational, cross-sectional study.


METHODS
Three hundred thirty eyes (88 with glaucoma, 206 glaucoma suspects, 36 healthy) from 208 individuals enrolled in the Diagnostic Innovations in Glaucoma Study (DIGS) were imaged using RTVue, Spectralis and Cirrus in a single visit. Agreement among RNFL thickness measurements was assessed using Bland-Altman plots. The influence of age, axial length, disc size, race, spherical equivalent, and disease severity on the pairwise agreements between different instruments was assessed by regression analysis.


RESULTS
Although RNFL thickness measurements between different instruments were highly correlated, Bland-Altman analyses indicated the presence of fixed and proportional biases for most of the pairwise agreements. In general, RTVue measurements tended to be thicker than Spectralis and Cirrus measurements. The agreement in average RNFL thickness measurements between RTVue and Spectralis was affected by age (P = .001) and spherical equivalent (P < .001), whereas the agreement between Spectralis and Cirrus was affected by axial length (P = .004) and spherical equivalent (P < .001). Disease severity influenced the agreement between Spectralis and both RTVue and Cirrus (P = .001). Disc area and race did not influence the agreement among the devices.


CONCLUSIONS
RNFL thickness measurements obtained by different SD-OCT instruments were not entirely compatible and therefore they should not be used interchangeably. This may be attributable in part to differences in RNFL detection algorithms. Comparisons with histologic measurements could determine which technique is most accurate.
Hamilton Glaucoma Center, Department of Ophthalmology, University of California San Diego, La Jolla, USA.
Mauro T
MT
Leite
Harsha L
HL
Rao
Robert N
RN
Weinreb
Linda M
LM
Zangwill
Christopher
C
Bowd
Pamela A
PA
Sample
Ali
A
Tafreshi
Felipe A
FA
Medeiros
D000367:Age Factors; D000368:Aged; D003430:Cross-Sectional Studies; D005006:Ethnicity; D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009798:Ocular Hypertension / Q000175:diagnosis; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D010781:Photography; D015203:Reproducibility of Results; D012165:Retinal Ganglion Cells / Q000473:pathology*; D041623:Tomography, Optical Coherence / Q000295:instrumentation*; D058609:Visual Field Tests