Longitudinal Macular Structure-Function Relationships in Glaucoma and Their Sources of Variability

Abstract

To review central structure-function (SF) relationships in glaucoma; to compare contributions of within-session and between-session variability to total variability of macular optical coherence tomography (OCT) thickness measurements; and to 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 33 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. One hundred twenty eyes with ‡3 10 8 visual fields (VFs)/OCT images were enrolled for the longitudinal study. We investigated within-eye longitudinal SF relationships (GCIPL thickness vs VF total deviations) with a change-point regression model and compared within-eye to between-individual variabilities with components-of-variance models. RESULTS: In the cross-sectional study, the betweensession component contributed 8%, 11%, 11%, and 36% of total variability for GCL, GCIPL, GCC, and FMT, respectively. In the longitudinal study, betweenindividual variability explained 78%, 77%, and 67% of total SF variability at 3.4 8 , 5.6 8 , and 6.8 8 eccentricities, respectively (P < .05). SF 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.

Longitudinal Macular Structure–Function Relationships in Glaucoma

“…Our group has demonstrated that SF relationships varied as a function of distance from the fovea. 15,27 Raza et al 24 investigated SF relationships at 5 different distances from the fovea and reported that the highest correlation was seen at 7.2 eccentricity. In this study, the highest correlation was observed at 3.4 and 5.6 eccentricities (circles 1 and 2) depending on the change measure explored.…”

“…This is consistent with findings by Miraftabi et al 34 and is probably related to the fact that the macular thickness is at its maximum at 5.6 from the fovea. 27 Macular thickness measures are more likely to reach their floor sooner or be more variable outside this region.…”

“…24,26 We recently demonstrated that within-eye SF relationships over time demonstrated less variability compared with those observed in a pooled sample of eyes. 27 Therefore, changes in structural and functional measurements within individual eyes over time may be more likely to be correlated compared with cross-sectional measurements. However, factors such as foveal shape, fovea-disc axis angle, and location of the temporal raphe, among others, may affect the spatial and temporal aspects of such correlations.…”

Optical coherence tomography and optical coherence tomography angiography in glaucoma: diagnosis, progression, and correlation with functional tests

“…GCC and FMT). 52,53 In addition, thinner measures are limited by narrower dynamic ranges and increased variability in severe glaucoma, likely related to segmentation errors which are more frequent with thinner retinal layers. 54 In yet unpublished studies, GCC was the best outcome measure to monitor glaucoma progression along the entire disease spectrum and provided the best Although MRW is a promising measure to diagnose patients with early glaucoma, few studies suggest that it may perform worse or, at least, equal to pRNFL to monitor disease progression.…”

“…GCC and FMT). 52,53 In addition, thinner measures are limited by narrower dynamic ranges and increased variability in severe glaucoma, likely related to segmentation errors which are more frequent with thinner retinal layers. 54 In yet unpublished studies, GCC was the best outcome measure to monitor glaucoma progression along the entire disease spectrum and provided the best longitudinal structure–function relationship with central VF (Nouri- Mahdavi et al “Comparison of rates of progression of macular OCT parameters in glaucoma.” Paper presented at: 2018 ARVO annual meeting, Honolulu, HI, USA.…”