Retina thickness in atypical parkinsonism: a systematic review and meta-analysis

Background and purpose To investigate the retina thickness assessed using optical coherence tomography in atypical parkinsonism in comparison with health controls (HC) and patients with Parkinson’s disease (PD). Methods PubMed and EMBASE were searched for potentially eligible studies that reported retina thickness in atypical parkinsonism [including progressive supranuclear palsy (PSP), multiple system atrophy (MSA) and corticobasal degeneration] in comparison with that of HC and PD patients from their dates of inception to Jan 24, 2021. Mean difference (μm) of the thickness of peripapillary retinal nerve fiber layer (pRNFL) and central macular thickness (CMT) were pooled with random effects model. Results We included ten studies eligible for inclusion criteria. Average pRNFL thickness and average CMT were thinner in PSP [pooled mean difference (μm) of − 4.71, 95% CI (− 7.15, − 2.27); − 15.12, 95% CI (− 16.93, − 13.30)] and in MSA [− 5.37, 95% CI (− 6.59, − 4.15); − 5.93, 95% CI (− 11.00, − 0.87)] compared with HC, and were thinner in PSP [− 5.81, 95% CI (− 8.92, − 2.69); − 10.63, 95% CI (− 20.29, − 0.98)] and in MSA [− 0.35 μm, 95% CI (− 5.72, 5.01); − 7.42 μm [95% CI (− 12.46, − 2.38)] compared with PD. The pRNFL thickness was thinning in superior, inferior and nasal quadrants, and CMT was thinning in outer sectors in MSA compared with HC. Conclusions The retina thickness was significantly thinner in PSP and MSA than those in HC and PD. The specific patterns of retina thinning in MSA could be clinical importance for differentiation among atypical parkinsonism.