Abstract
Purpose: :
To determine the correlation, and compare glaucoma diagnostic abilities of the peripapillary retinal nerve fiber layer (RNFL) thickness measurements and the central angle measurements of RNFL thinning obtained using the Cirrus HD-OCT device (Carl Zeiss Meditec, Dublin, CA).
Methods: :
A retrospective, cross-sectional study was performed on 191 eyes from 97 glaucoma subjects (57 eyes with mild glaucoma, 40 eyes with moderate glaucoma, and 60 with severe glaucoma), 128 eyes from 65 glaucoma suspects, and 58 eyes from 30 healthy subjects. Patient group assignment was based on Hodapp-Anderson-Parrish Visual Field criteria.RNFL thickness measurements were obtained from the RNFL Thickness Analyses of the Optic Disc Cube 200x200 scans. Using the Deviation from Normal Maps, the arc segments were plotted where the "red areas" (RNFL thickness <1% of normative data) intersected the Calculation Circle. Central angles were then calculated using a geometric formula and recorded in degrees.Area-under-receiver operator curves (AUC) were calculated for three RNFL thickness measures (average thickness, superior quadrant and inferior quadrant), and three central angle measurements (superior, inferior, and superior + inferior quadrants) using SAS 9.2. Two-tailed, Pearson’s correlation coefficients for the RNFL thickness and central angle measurements were also calculated using SPSS 16.0.
Results: :
There is a significant inverse relationship between RNFL thickness measurements and central angle measurements of RNFL thinning. Pearson’s coefficients obtained are as follows: Average RNFL thickness and Superior+Inferior Central Angle (r=-0.735, p<0.01), Superior Quadrant (r=-0.713, p<0.01) and Inferior Quadrant (r=-0.747, p<0.01). RNFL thickness measurements were good parameters for all glaucoma stages, generating AUCs greater than 0.8. Central angle measurements of RNFL thinning were less sensitive, with AUCs ranging from 0.52 to 0.93.
Conclusions: :
RNFL thickness measurements and central angle measurements of RNFL thinning were found to be highly correlated. However, RNFL thickness measurements have a higher sensitivity in glaucoma detection compared to central angle measurements of RNFL thinning.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical