LAUSR

PURPOSE 1) Review central structure-function (SF) relationships in glaucoma; 2) compare contributions of within-session and between-session variability to total variability of macular optical coherence tomography (OCT) thickness measurements; and 3) test the hypothesis that longitudinal within-eye variability of central SF relationships is smaller than between-individual variability. METHODS We reviewed the pertinent literature on central SF relationships in glaucoma. Thirty-eight eyes (20 normal or glaucoma subjects) had ×3 macular images per session over 3 sessions and superpixels thickness measurements for ganglion cell layer (GCL), ganglion cell/inner plexiform layer (GCIPL), ganglion cell complex (GCC) and full macular thickness (FMT) were exported. Linear mixed models were used for estimating contributions of between- and within-session variability to total thickness variability. 120 eyes with ≥3 10° visual fields (VFs)/OCT images were enrolled for the longitudinal study. We investigated within-eye longitudinal SF relationships (GCIPL thickness vs. VF test locations) with a change-point regression model and compared within-eye with between-individual variabilities with components-of-variance models. RESULTS In the cross-sectional study, between-session component contributed 8%, 11%, 11%, and 36% of total variability for GCL, GCIPL, GCC, and FMT. In the longitudinal study, between-individual variability explained 78%, 77%, and 67% of total SF variability at 3.4°, 5.6°, and 6.8° eccentricities (P<0.05). Structure-function relationships remained stable over time within individual eyes. CONCLUSIONS Within-session variability accounts for most of macular thickness variability over time. Longitudinal within-eye SF variability is smaller than between-individual variability. Study of within-eye SF relationships could help clinicians better understand SF linking in glaucoma and help refine progression algorithms.