Abstract
Purpose :
Measurements of choroidal thickness (CT) with optical coherence tomography (OCT) have been used in cross-sectional studies to investigate whether glaucoma patients have thinner CT than controls to establish a vascular link to glaucoma. However, the literature shows conflicting results. Longitudinal studies could be advantageous to evaluate the relationship between CT and glaucoma, since the effects of inter-individual variability are reduced. We tested the hypothesis that glaucoma patients with progressive thinning of the choroid would also have faster loss of the neuroretinal parameters, including minimum rim width (MRW) and retinal nerve fibre layer thickness (RNFLT).
Methods :
We included one eye of 155 open angle glaucoma patients followed in a longitudinal observational study. OCT imaging was performed at 6-month intervals. Global MRW and RNFLT were measured, respectively, by 24 radial optic nerve head scans and a 3.5 mm diameter peripapillary scan. CT was measured at 2 positions in each radial scan (at diameters of 3.4 and 3.6 mm). We evaluated the association of longitudinal changes in CT with MRW and RNFLT, with a linear mixed effect model for each neuroretinal parameter. The models also included intraocular pressure for each visit, baseline age and baseline CT to explore their effect on longitudinal changes of CT.
Results :
Baseline characteristics of glaucoma patients were (mean and standard deviations): age of 69.78 (9.43) years, visual field mean deviations of -5.03 (4.37), MRW of 181.73 (48.95) µm, RNFLT of 69.28 (12.79) µm. The mean follow-up was 3.90 (range, 2.03 to 5.44) years. Longitudinal changes of CT correlated with changes in MRW (coefficient = 0.16 [95% confidence interval: 0.08 to 0.23] µm/µm, p<0.01), but not with changes in RNFLT (-0.09 [-0.30 to 0.13] µm/µm, p=0.41). For both models, longitudinal changes of CT correlated with intra-ocular pressure (-0.57 µm/mmHg, p <0.01), baseline choroidal thickness (-0.02 µm/y per µm, p <0.01), but not with baseline age (0.03 µm/y per y, p ≥0.24).
Conclusions :
Longitudinal changes in CT were associated with changes in MRW. However, because a similar association was not observed between longitudinal changes of CT and RNFLT, it is unclear whether CT changes are related to glaucoma progression.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.