Comparison of Peripapillary Choroidal Thickness between Primary Open Angle Glaucoma, Normal Tension Glaucoma and Normal Eyes: A Systematic Review and Meta-Analysis

To investigate differences in peripapillary choroidal thickness (PPCT) between primary open-angle glaucoma (POAG), normal tension glaucoma (NTG) and healthy eyes, additionally comparing differences between POAG and NTG eyes. Peripapillary choroidal thickness (PPCT) is a well-established optical coherence tomography (OCT) parameter in eyes with glaucoma and other ocular pathologies. The relationship between PPCT and glaucoma, if better understood, may facilitate the development of PPCT as a potential diagnostic and monitoring metric for glaucoma. In particular, there has yet to be a synthesis that directly compares PPCT between POAG eyes and NTG eyes. A comprehensive literature search was performed on PubMed, EMBASE and Cochrane Library, identifying studies from inception to December 2022. We included studies that measured PPCT using optical coherence tomography (OCT) in POAG, NTG, and healthy eyes. Mean difference (MD) among groups was calculated. Statistical analysis was performed using R version 4.2.0. Risk of bias of included studies was assessed using the Newcastle Ottawa Scale (NOS). Eighteen studies were included in this meta-analysis, with a pooled total of 935 healthy control eyes, 446 NTG eyes and 934 POAG eyes. There was a significant reduction of PPCT in POAG eyes compared with healthy eyes [MD = -16.32, 95% CI (-27.55, -5.09)]. Reduction in PPCT was also significant in NTG eyes compared with healthy eyes [MD = -34.96, 95% CI (-49.97, -19.95)]. NTG eyes had significantly reduced PPCT compared with POAG eyes [MD = -26.64, 95% CI (-49.00, -4.28)]. Glaucomatous eyes appear to have significantly reduced PPCT compared to normal healthy eyes. In addition, PPCT in NTG eyes appear significantly thinner compared with that in POAG eyes.