Analysis of retinal microvasculature features in amblyopic eyes: A meta-analysis

Background: Amblyopia is a common cause of visual disorder with several changes in retinal structure and vessel. To date, alterations in retinal microvasculature features in amblyopia have yielded inconsistent results. Objectives: This meta-analysis aimed to evaluate retinal vessel density (VD) in amblyopic patients using optical coherence tomography angiography (OCTA). Methods: PubMed, Web of Science, Embase, and Cochrane Library databases were systematically searched for published articles comparing retinal microvasculature characteristics in patients with amblyopia and controls. Continuous variable outcomes were assessed using the mean difference (MD) with a 95% confidence interval. Review Manager Version 5.30 was used for the analysis. Results: Thirteen qualified articles were pooled in this meta-analysis. Compared with controls, the foveal whole enface VD of superficial (SCP) and deep capillary plexus (DCP) of patients as measured by 3x3-mm scans were significantly lower in amblyopia eyes (MD:-1.37, P = 0.0003; MD: 1.70, P < 0.00001, respectively). Similarly, in the 6x6-mm scans, foveal whole enface VD of the SCP and DCP were remarkably lower in amblyopia eyes than in controls (MD:-2.24, P = 0.03; MD:-5.08, P = 0.04, respectively). The parafoveal VD of SCP in 3x3-mm scans (MD: 1.96, P < 0.00001) was also lower in amblyopic patients than in controls. Similarly, in 6x6-mm scans, amblyopia eyes showed a significant decrease, and a trending decrease in the parafoveal VD of the SCP (MD:-3.85, P = 0.007) and DCP (MD:-3.03, P = 0.10), respectively. For whole radial peripapillary capillary (RPC), VD was significantly reduced in amblyopic patients compared to controls (MD =-0.83, P < 0.00001). In addition, the deep foveal avascular zone (FAZ) was larger in amblyopic eyes than in the controls (MD = 0.55, P= 0.007). Conclusions: Our data suggest that whole foveal and parafoveal VD and RPC whole VD were reduced in patients with amblyopia. Moreover, our results reveal that the FAZ is larger in amblyopic patients. Consequently, OCTA may have the potential for diagnosing and monitoring patients with amblyopia.