Central retina changes in Parkinson’s disease: a systematic review and meta-analysis

Central retina imaging is important for early Parkinson’s disease (PD) recognition. We aimed to investigate central retina changes using spectral domain-optical coherence tomography (SD-OCT) in PD patients. We systematically searched PubMed and EMBASE to identify studies comparing the whole or individual layer thickness of central retina between PD patients and health controls using SD-OCT from inception to April 25, 2020. Data were extracted at eye level. We pooled the mean difference with random effects model. Subgroup analysis and mete-regression were done to detect possible source of heterogeneity. We included 27 studies (28 sets of data) enrolling 1470 PD patients (2288 eyes) and 1552 health controls (2524 eyes) in our meta-analysis. Compared with control eyes, the whole thickness of central retina decreased significantly at fovea center by mean difference − 2.70 μm (95% CI [− 4.87, − 0.53], p = 0.01) and in all quadrants in PD eyes. The combination of ganglion cell layer and inner plexiform layer thinned by an average mean difference of − 3.17 μm (95% CI [− 5.07, − 1.26], p = 0.001). The nerve fiber layer thinned by an average mean difference − 0.66 μm (95% CI [− 1.09 to − 0.23], p = 0.003). There was no significant difference in the thickness of inner nuclear layer, outer plexiform layer and outer nuclear layer between eyes of PD and controls. The results of subgroup analysis and mete-regression were consistent. The whole thickness, the thickness of the combination of ganglion cell layer and inner plexiform layer, and nerve fiber layer of central retina decreased significantly in PD patients.