Comparison between fixed-angle and customised corneal-polarisation compensation methods in scanning laser polarimetric measurement of the retinal nerve fibre layer in glaucoma

Abstract

Purpose: To investigate the differences between the results of scanning laser polarimetric (SLP) measurements of the retinal nerve fibre layer thickness (RNFLT) made using two different corneal-polarisation techniques; customised (SLP-C), and fixed-angle (SLP-F) compensations. Methods: Both SLP-C and SLP-F were performed on 37 consecutive phakic patients with chronic open-angle glaucoma, and on 14 healthy control subjects. One randomly selected eye per subject was evaluated. Results: Both SLP-C and SLP-F parameters were able to discriminate between the glaucoma group and the control group, except in the case of the ellipse modulation, which differed significantly between the two groups with SLP-C (P = 0.017), but not with SLP-F (P = 0.056). When SLP-C and SLP-F values were compared, inferior maximum thickness and ellipse standard deviation were significantly lower with SLP-C in both groups (P < 0.05 for each parameter). Superior maximum thickness was significantly lower in glaucoma with SLP-C than with SLP-F (P = 0.006) and tended to be lower with SLP-C than with SLP-F in the control group (P = 0.053). In the glaucoma group, it was only with SLP-C that a significant (positive) correlation between the superior maximum thickness and the inferior hemifield mean sensitivity (MS) (r = 0.653, P < 0.001), and between the inferior maximum thickness and the superior hemifield MS (r = 0.420, P = 0.023) was found. The other global and sectoral SLP parameters showed significant correlation with the corresponding visual field parameters with both techniques. Conclusion: Our findings suggest that SLP measurements with customised compensation provide more realistic results for RNFLT than those made with the conventional fixed-angle compensation. © 2005 Nature Publishing Group All rights reserved.