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 assess the relationship between high-definition optical coherence tomography (HD-OCT) and scanning laser polarimetry (SLP) with variable (VCC) and enhanced (ECC) corneal compensation in measuring peripapillary retinal nerve fibre layer (RNFL) thickness in healthy eyes and those with early-to-moderate glaucomatous VF loss.

Methods: Healthy volunteers and patients with glaucoma who met the eligibility criteria were enrolled in this prospective, cross-sectional, and observational study. Subjects underwent complete ophthalmologic examination, automated perimetry, SLP-ECC, SLP-VCC and HD-OCT. SLP parameters were recalculated in 90 degrees segments (quadrants) in the calculation circle to be compared. Pearson correlation coefficients and Lin's concordance correlation coefficients were calculated. The p-values < 0.05 were considered statistically significant.

Results: Fifty-five normal volunteers (mean age 59.1 years) and 33 patients with glaucoma (mean age 63.8 years) were enrolled. In the glaucoma group, 18 patients (54.5%) had MD ≥ -6.0 dB (early glaucoma) and 15 patients (45.4%) had MD between -6.01 and -12.0 dB (moderate glaucoma). The best correlation between HD-OCT and SLP was found in the superior quadrant thickness, r = 0.74 (0.62-0.82) (p < 0.0001) with SLP-VCC and in the average thickness, r = 0.80 (0.71-0.86) (p < 0.0001) and the superior quadrant thickness r = 0.80 (0.71-0.87) (p < 0.0001) with SLP-ECC. Concordance correlation coefficients obtained for every parameter in our study between HD-OCT and SLP-VCC and between HD-OCT and SLP-ECC were poor.

Conclusions: Our results suggest that HD-OCT parameters of RNFL thickness are significantly higher than SLP-VCC and SLP-ECC parameters, and therefore those thickness values are not interchangeable. The HD-OCT and SLP methods are well correlated but concordance is poor. The difference plots show a lack of agreement that changes as a proportion of the mean.