Changes in Retinal Nerve Fiber Layer Reflectance Intensity as a Predictor of Functional Progression in Glaucoma

We determined whether longitudinal changes in retinal nerve fiber layer (RNFL) reflectance provide useful prognostic information about longitudinal changes in function in glaucoma.

The reflectance intensity of each pixel within spectral-domain optical coherence tomography (SD-OCT) circle scans was extracted by custom software. A repeatability cohort comprising 53 eyes of 27 participants (average visual field mean deviation [MD] -1.65 dB) was tested five times within a few weeks. To minimize test-retest variability in their data, a reflectance intensity ratio was defined as the mean reflectance intensity of pixels within the RNFL divided by the mean between the RNFL and RPE. This was measured in a separate longitudinal cohort comprising 310 eyes of 205 participants tested eight times at 6-month intervals (average MD, -0.99 dB; median rate of change, -0.09 dB/y). The rate of change of this ratio, together with the rate of RNFL thinning, and their interaction, were used to predict the rate of change of MD.

In univariate analyses, the rate of RNFL thinning was predictive of the rate of MD change (P < 0.0001), but the rate of change of reflectance intensity ratio was not (P = 0.116). However, in a multivariable model, the interaction between these two rates significantly improved upon predictions of the rate of functional change made using RNFL thickness alone (P = 0.038).

For a given rate of RNFL thinning, a reduction in the RNFL reflectance intensity ratio is associated with more rapid functional deterioration. Incorporating SD-OCT reflectance information may improve the structure-function relation in glaucoma.