This analysis, including nearly 1,000 patients, is the first to compare PPCT in normal-tension glaucoma vs. primary open-angle glaucoma, finding that the latter was reduced with a mean difference of -26.64. Photo: Pedro Simões, Med Hypothesis Discov Innov Ophthalmol. 2018; 7(4). Click image to enlarge.

A well-established glaucoma parameter on OCT is peripapillary choroidal thickness (PPCT); however, to rely on this metric to help diagnose and monitor glaucoma, we must first have a clear understanding of how it differs in eyes with primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG) and healthy eyes. Researchers recently investigated this by performing a comprehensive literature search on numerous online databases, ultimately including a total of 935 healthy control eyes, 446 NTG eyes and 934 POAG eyes across 18 different studies.

Two main conclusions were drawn from the meta-analysis: (1) glaucomatous eyes appeared to have significantly reduced PPCT compared to healthy eyes (POAG, mean difference: -16.32; NTG, mean difference: -34.96), and (2) in NTG eyes, PPCT was significantly thinner than in POAG eyes (mean difference: -26.64).

A previous meta-analysis made the opposite observation—finding no difference in PPCT between glaucoma eyes and healthy eyes—but researchers of the present analysis argue that their work includes more up-do-date, vetted studies, therefore producing more trustworthy results. Also, as the authors point out in their paper in Ophthalmology, this study is “the first synthesis to date which compares PPCT directly between NTG eyes and POAG eyes.

“In conclusion,” the authors wrote, “our systematic review and meta-analysis has found that PPCT is significantly reduced in both POAG and NTG compared to healthy eyes, and in NTG compared to POAG eyes.” They added, “There are currently no normative baseline data values established for PPCT, and future work defining normative data values would be helpful in aiding the clinician to use PPCT as an adjunct or alternative diagnostic tool for NTG or POAG.”