Association between scanning laser polarimetry measurements using variable corneal polarization compensation and visual in field sensitivity glaucomatous eyes

Objective: To compare the association between scanning laser polarimetry (SLP) retinal nerve fiber layer (RNFL) measurements and automated perimetry sensitivity using both SLP manufacturer-assumed fixed and subject-specific variable corneal polarization magnitude and corneal polarization axis values. Main Outcome Measures: The relationship between regional SLP RNFL measurements (24 parameters) and corresponding regional SITA raw thresholds were evaluated using linear regression for both (fixed corneal compensation and variable corneal compensation) SLP configurations. Methods: An SLP was modified to enable the measurement of corneal polarization magnitude and corneal polarization axis so that compensation for corneal birefringence could be corrected on a subject-specific variable basis. Seventy-three eyes from the University of California, San Diego, Diagnostic Innovations in Glaucoma Study with early glaucoma or suspected glaucoma (abnormal Swedish Interactive Threshold Algorithm [SITA] or full-threshold automated perimetry results and/or glaucomatous-appearing optic disc by consensus grading of stereoscopic optic disc photographs) (mean [SD] SITA mean deviation, -2.74 [3.71] dB; range, 1.72 to -14.72 dB) were included. Subjects were imaged with SLP using the manufacturer-assumed fixed corneal compensation values and subject-specific variable corneal compensation values and tested with SITA automated perimetry. Scanning laser polarimetry and SITA data were obtained within 3 months of each other. Main Outcome Measures: The relationship between regional SLP RNFL measurements (24 parameters) and corresponding regional SITA raw thresholds were evaluated using linear regression for both (fixed corneal compensation and variable corneal compensation) SLP configurations. Results: No fixed corneal compensation SLP measurements were significantly associated with corresponding SITA visual field zone sensitivities after corrections for multiple comparisons. Seven variable corneal compensation RNFL parameters (superior, inferior, or mean RNFL thickness measurements) were significantly associated with their corresponding visual field zones with R-2 values ranging from 0.13 (ellipse average) to 0.20 (superior average). Conclusion: Variable corneal compensation to correct for subject-specific corneal polarization magnitude and corneal polarization axis improves the relationship between SLP-measured RNFL thickness and visual function measured by SITA perimetry.