Quantitative analysis of microvasculature in macular and optic disc regions in keratoconus patients: a systematic review and meta-analysis

Studies have utilized optical coherence tomography angiography (OCTA) to assess vessel density in the macular and optic disc regions among patients with keratoconus (KC); however, the findings have been incongruent. This study aimed to systematically investigate the retinal macular and optic disc microvascular characteristics in patients with KC compared to healthy controls using OCTA. A comprehensive literature search was performed across multiple electronic databases, including PubMed, Embase, Web of Science, and the Cochrane Library, up to April 2025. The vessel density metrics of the macular and optic disc regions were extracted and analyzed for both keratoconus patients and healthy controls. Mean differences (MDs) with 95% confidence intervals were calculated to compare continuous variables. Statistical analyses were conducted using Review Manager Version 5.4.1 software. A total of six studies were included in our analysis. The results demonstrated that the macular whole enface superficial vessel density was significantly lower in the keratoconus (KC) group compared to the control group (MD = -4.45, P < 0.00001). Additionally, there were significant differences in foveal superficial and deep vessel densities between the two groups (MD = -3.27, P = 0.001; MD = -3.58, P = 0.0003, respectively). The parafoveal superficial vessel density in the KC group was markedly reduced compared to that of the controls (MD = -6.21, P = 0.0004). For perifoveal vessel density, patients with KC exhibited significantly decreased vessel density in both the superficial and deep capillary plexuses compared to the control group (MD = -5.12, P < 0.00001; MD = -9.16, P = 0.01, respectively). Furthermore, the radial peripapillary capillary (RPC) whole image vessel density was substantially lower in KC eyes than in the control group (MD = -0.89, P = 0.02). The current meta-analysis demonstrated that the vascular density in the macular and optic nerve head regions was reduced in patients with KC, suggesting that retinal microvasculature could serve as a potential biomarker for aiding in the diagnosis of KC.