Abstract
Abstract: :
Purpose: To determine the association between nerve fiber layer measurement using scanning laser polarimetry and optical coherence tomography, and to examine the effect of SLP measured macular birefringence on this association. Background: Scanning laser polarimetry measurements of the nerve fiber layer have been shown to be significantly influenced by the axis and amplitude of corneal birefringence, introducing inaccuracies in measurements that can vary widely between individuals. Measuring macular birefringence has been suggested as a potential method of compensating for this corneal component. Methods: 63 eyes of 38 non-consecutive patients from a tertiary glaucoma service were included. SLP measurements of the peripapillary area and macula along with peripapillary nerve fiber layer measurements of average thickness using OCT were performed. Correlation coefficients between four SLP parameters and OCT average thickness were calculated. Results: Taking all comers, weak correlations were found between OCT measured NFL thickness and SLP neural network "number" (r2=.29, fig.1), ellipse modulation (r2=.18), maximum modulation (r2=.27), and average thickness (r2=.34). SLP in eyes with lower macular birefringence (macular SLP average thickness <45, 31 eyes) had significantly better correlation with OCT (r2=.59, .46, .55, and .57 respectively, fig.2) (P<.001 for all correlation coefficients) Conclusion: There is a weak correlation between nerve fiber layer measurements by SLP and OCT when corneal birefringence is not properly compensated for. This correlation is improved in eyes with lower measured macular birefringence, likely indicating a lower uncompensated corneal birefringence component in these eyes. This suggests that SLP using a device without a variable corneal polarization compensator should include scanning of the macula first to determine the corneal component and by extension the relative accuracy of the peripapillary nerve fiber layer measurements.
Keywords: 484 nerve fiber layer • 432 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 430 imaging/image analysis: clinical