Correlation Between Scanning Laser Polarimetry With and Without Enhanced Corneal Compensation and High Definition Optical Coherence Tomography in Normal and Glaucomatous Eyes

Abstract

Purpose: : To examine the association between scanning laser polarimetry (SLP) using enhanced (ECC) and variable corneal compensation (VCC) with High Definition optical coherence tomography (HD-OCT)

Methods: : A cross-sectional study of 86 normal and glaucomatous eyes who underwent complete examination, automated perimetry, SLP-ECC, SLP-VCC and HD-OCT. SLP parameters are recalculated in 90 degrees segments (quadrants) in the calculation circle to be compared. Differences between main parameters of retinal nerve fiber layer thickness are observed (average thickness, superior, inferior, temporal and nasal quadrants) and Pearson’s correlation coefficients are calculated. Bland & Altman plots are used to evaluate agreement between methods

Results: : HD-OCT parameters of RNFL thickness (average thickness 81,04 microns, SD18,8) are significantly higher than SLP-VCC parameters (average thickness 48,77 microns, SD 9,3) (p<0,0001) and SLP-ECC parameters (average thickness 45,63 microns, SD 9,2) (p<0,0001). Correlation coefficients between HD-OCT and SLP are: average VCC thickness r= 0,67 (p<0,0001), superior VCC quadrant r= 0,76 (p<0,0001), inferior VCC quadrant r= 0,7 (p<0,0001), temporal VCC quadrant r= 0,09 (p=0,389), nasal VCC quadrant r= 0,45 (p<0,0001), average ECC thickness r= 0,81 (p<0,0001), superior ECC quadrant r= 0,83 (p<0,0001), inferior ECC quadrant r= 0,75 (p<0,0001), temporal ECC quadrant r= 0,34 (p=0,0017), nasal ECC quadrant r= 0,47 (p<0,0001). There is no significant statistical difference in OCT-SLP correlation coefficients between VCC and ECC except for RNFL average thickness (p<0,04). Bland & Altman plots show a significant association between mean values of average RNFL thickness measured with SLP-VCC and HD-OCT and the difference of average RNFL thickness measured with the same methods (r= -0,71; p<0,0001) and also show a significant association between mean values of average RNFL thickness measured with SLP-ECC and HD-OCT and the difference of average RNFL thickness measured with the same methods (r= -0,77; p<0,0001)

Conclusions: : HD-OCT parameters of RNFL thickness are significantly higher than SLP-VCC and SLP-ECC parameters. HD-OCT and SLP methods are well correlated but the difference plots show a lack of agreement that changes as a proportion of the mean

Keywords: imaging/image analysis: clinical • nerve fiber layer