Abstract
Purpose: :
To compare the sensitivity and specificity of measurements of retinal nerve fiber layer (RNFL) thickness in mild to moderate glaucoma using time domain (Stratus) and spectral domain (Cirrus) Optical Coherence Tomography for manifest perimetric glaucoma.
Methods: :
Cross-sectional observational study consisting of fifty four early to moderate glaucoma subjects and fifty age-matched normal subjects. Three peripapillary RNFL scans of a single dilated eye of each patient, using both Stratus Fast and Cirrus OCT, were obtained. The highest quality scan with a minimum signal score of six was used. Outcome measures included sensitivity and specificity of average, quadrant, and clock hour (CH) RNFL thickness for the various OCT parameters and the area under the receiver operating characteristic curves (AROC).
Results: :
The average age (+/- standard deviation, range) in the normal and glaucoma groups was 62.9 years (SD±12.7, 40-84) and 67.6 years (SD±11.4, 42-85) respectively (P = 0.05). By standard visual field (VF) criteria, the glaucoma group consisted of 34 mild (avg. MD -3.20 dB, SD±1.22) and 20 moderate glaucomas (avg. MD -8.05 dB, SD±1.87). The RNFL value cutoffs at the 5% and 1% levels were defined by each machine’s built-in age-adjusted normative database.(below)A ROC curve based on logistic regression prediction equations was created for each instrument using the number of 5% (Nch5%) and 1% (Nch1%) affected clock hours, where the higher the number of abnormal clock hours, the more sensitive and specific the tests were for glaucoma.Cirrus probability of glaucoma = 0.77*Nch5% +2.16*Nch1% -2.37; AROC=0.97±0.2Stratus probability of glaucoma = 0.91*Nch5%+1.84*Nch1% -2.53; AROC=0.95±0.2
Conclusions: :
The sensitivity and specificity of RNFL measurements using the new Cirrus OCT for glaucoma with early to moderate VF defects are excellent and equivalent to Stratus OCT. The best overall parameter for both machines appears to be a single quadrant abnormal at the 5% level. For Cirrus, 1 quadrant at the 1% level improves the sensitivity over Stratus while maintaining specificity. Overall, the sensitivity and specificity cutoffs are similar for Cirrus and Stratus OCT.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • nerve fiber layer • imaging/image analysis: clinical