Abstract
Purpose: :
To assess diagnostic ability in glaucoma detection of retinal nerve fiber layer (RNFL) thickness measurements obtained by GDx ECC and Spectral-domain optical coherence tomography (RTVue and Spectralis OCT) and to compare the three instruments. To evaluate the diagnostic ability in glaucoma detection of the Ganglion Cell Complex (GCC) parameter available on RTVue OCT.
Methods: :
205 patients (70 Normal, 65 Ocular Hypertensive and 70 Glaucomatous) underwent a complete examination, standard automated perimetry (Humphrey 24/2 Sita Standard), pachimetry and RNFL assessment by means of GDx-Pro, FD OCT (RTVue-Optovue Inc; Spectralis Heidelberg Engineering). Areas under the receiver operating characteristic curves (AUROCs) and sensitivity values at a fixed specificity of 95% with 95% Confidence Intervals (CI) were calculated and compared for RNFL parameters obtained by the instruments. Agreement between RNFL measurements obtained by RTVue and Spectralis was evaluated by means of Bland-Altman plots.
Results: :
The best RNFL parameters are NFI (AUC 0.99, sensitivity 96%) for GDx, "Average" (AUC 0.98, sensitivity 90%) , Inferior-Temporal (AUC 0.97, sensitivity 89%) and Superior-Temporal (AUC 0.96, sensitivity 87%) for RTVue OCT and "Global Average" (AUC 0.99, sensitivity 94%) for Spectralis OCT, with no significant difference between the three devices (P>0.05)The best GCC parameters are FLV% (AUC 0.98, sensitivity 91%) and GLV% (AUC 0.96, sensitivity 87%). Bland and Altman analysis indicate the presence of fixed biases for all the RNFL measurements (P <0.001) and of proportional biases for all the parameters (P <0.001), except for temporal sector. RNFL layer measurements obtained by RTVue tended to be thicker than those obtained by Spectralis.
Conclusions: :
GDx ECC and both OCT show a good diagnostic ability in glaucoma detection and have comparable diagnostic performance. Elevated values of AUC and high sensitivity values for most RNFL parameters. GCC thickness measurements show excellent diagnostic validity and may be a very useful parameter in early detection of RNFL damage. RNFL thickness measurements obtained by different OCT were not entirely comparable and they should not be used interchangeably.
Keywords: nerve fiber layer • imaging/image analysis: clinical • optic disc