Regression Analysis in the Structural–Functional Relationship in Glaucoma Using Optical Coherence Tomography (OCT) and Scanning Laser Polarimetry (SLP)

Abstract

Abstract: : Purpose:To evaluate and compare the structural–functional relationship between visual field sensitivity and retinal nerve fiber layer thickness (RNFLT)measured by OCT and SLP. Methods: A total of 102 eyes (49 normal and 53 glaucoma) from 65 subjects were enrolled in this cross sectional study. RNFLT was measured with OCT (Stratus OCT) and SLP (GDx VCC) and visual field was examined with Humphrey visual field analyzer. Relationship between RNFLT and perimetry, expressed both in the standard decibel (dB) scale and in the unlogged 1/Lambert (L) scale, was evaluated with linear and non–linear regression (quadratic, logarithmic, inverse and power) models. Coefficient of determination (R²) was calculated and the regression models were compared with Alkaike’s Information Criteria (AIC). Results: Plotting visual field mean deviation in dB against RNFLT, quadratic regression demonstrated the highest coefficient of determination (R² = 0.76 and 0.66 with OCT and SLP measured RNFLT respectively). When the perimetry scale was expressed with the unlogged 1/L, the coefficients of determination were 0.67 and 0.62 in linear regression, and 0.67 and 0.64 in quadratic regression, for OCT and SLP measurements respectively. Comparing the linear and quadratic models, the relationship was better fit with linear regression (difference in AIC score=2.145) when the RNFLT was measured by OCT, and quadratic regression (difference in AIC score=3.891) when it was measured by SLP. OCT generated RNFLT had higher coefficients of determination compared to that of SLP in both linear and non–linear regression analysis with visual field indexes. Conclusions: The description of the visual field function and the RNFLT relationship in glaucoma was dependent on the choice of the perimetery scale and the type of RNFL measuring devices. The structural–functional relationship was curvilinear when the perimetry was expressed in decibel. However, when it was expressed with the unlogged 1/L scale, the relationship was best described with linear model in OCT measurements, and non–linear model in SLP measurement. OCT measured RNFLT was found to have a stronger association with visual function.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)