Retinal Nerve Fiber Layer Thickness Changes in Parkinson Disease: A Meta-Analysis

Background: Parkinson disease (PD) is a neurodegenerative process that leads to a selective loss of dopaminergic neurons, mainly in the basal ganglia of the brain. Numerous studies have analyzed the ability of optical coherence tomography (OCT) to detect retinal nerve fiber layer (RNFL) thickness abnormalities and changes in PD, but the results have not always been consistent. Therefore, we carried out a meta-analysis to evaluate the RNFL thickness measured with OCT in PD. Methods and Findings: Case-control studies were selected through an electronic search of the Cochrane Controlled Trials Register, PUBMED and EMBASE. For the continuous outcomes, we calculated the weighted mean difference (WMD) and 95% confidence interval (CI). The statistical analysis was performed by RevMan 5.0 software. Thirteen case-control studies were included in the present meta-analysis, containing a total of 644 eyes in PD patients and 604 eyes in healthy controls. The results of our study showed that there was a significant reduction in average RNFL thickness in patients with PD compared to healthy controls (WMD = -5.76, 95% CI: -8.99 to -2.53, P = 0.0005). Additionally, differences of RNFL thickness in superior quadrant (WMD = -4.44, 95% CI: -6.93 to -1.94, P = 0.0005), inferior quadrant (WMD = -7.56, 95% CI: -11.33 to -3.78, P<0.0001), nasal quadrant (WMD = -3.12, 95% CI: -5.63 to -0.61, P = 0.01) and temporal quadrant (WMD = -4.63, 95% CI: -7.20 to -2.06, P = 0.0004) were all significant between the two groups. Conclusion: In view of these results and the noninvasive nature of OCT technology, we surmise that OCT could be a useful tool for evaluating the progression of the Parkinson disease.