The specific pattern of retinal nerve fiber layer thinning in Parkinson’s disease: a systematic review and meta-analysis

Background and purpose The peripapillar nerve fiber layer (pRNFL) thinning in different retinal quadrants or sectors remains controversy. We conducted a systematic review and meta-analysis on the pattern of pRNFL thinning in Parkinson’s disease (PD) patients to provide a biomarker for PD differential diagnosis. Methods We systematically searched PubMed and EMBASE to identify studies comparing pRNFL thickness in PD patients and health controls using spectral domain-optical coherence tomography from inception to April 25, 2020. Random effects mode was used to pool mean difference (μm) of the average thickness of pRNFL and the thickness of pRNFL in four quadrants (superior, inferior, nasal and temporal) and in the subdivisions of superior (superonasal and superotemporal sectors) and inferior quadrants (inferonasal and inferotemporal sectors) between PD patients and health controls. Results We included 32 studies (33 sets of data) enrolling 2126 PD eyes and 2318 health control eyes. Between the eyes of PD patients and that of health controls, the pooled mean difference (μm) of average pRNFL was − 4.85 (95% CI [− 6.12, − 3.58]); the pooled mean difference (μm) of four quadrants were − 2.30 (95% CI [− 3.32, − 1.28], nasal), − 2.74 (95% CI [− 4.34, − 1.14], temporal), − 5.24 (95% CI [− 7.04, − 3.43], superior) and − 7.29 (95% CI [− 9.23, − 5.34], inferior); those of four sectors were − 5.16 (95% CI [− 7.70, − 2.62], superotemporal), − 3.55 (95% CI [− 5.87, − 1.23], superonasal), − 9.19 (95% [− 13.27, − 5.12], inferotemporal) and − 7.62 (95% CI [− 11.84, − 3.40], inferonasal). Conclusion In PD patients, pRNFL thinning followed a specific pattern with inferotemporal thinning most and nasal quadrant thinning least.