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Table 1 Studies investigating corneal confocal microscopy (CCM) in Parkinson’s disease (PD)

From: Potential use of corneal confocal microscopy in the diagnosis of Parkinson’s disease associated neuropathy

StudiesAimsStudy cohortMain findingsReference
Kass-Iliyya et al. (2015)To determine whether CCM can demonstrate small nerve fiber damage in PD. To identify relationships between CNP, IENFD and clinical features of PD.cross-sectional (52 subjects: 26 PD, 26 controls)CNFD was reduced but CNBD and CNFL were increased in PD compared to healthy controls. CNBD and CNFL but not CNFD correlated inversely with UPDRS-III and SCOPA-AUT. IENFD is also reduced and correlates with CNFD and motor symptoms.[6]
Podgorny et al. (2016)To determine if peripheral neuropathy occurs in early untreated PD.cross-sectional (48 subjects: 26 PD, 22 controls)CNFL, CNBD, CNFD were reduced in PD compared to healthy controls, but CNFD didn’t have significantly difference. NCS and IENFD found no significant difference between groups.[7]
Misra et al. (2017)To examine the ocular surface in patients with moderately severe PD.cross-sectional (30 subjects: 15 PD, 15 controls)Corneal sub-basal nerve plexus density was markedly reduced in patients with PD compared with controls. Sub-basal corneal nerve density was a significant positive correlation between ACE-R scores.[8]
Reddy et al. (2013)To examine the ocular surface in patients with PSP and PD.cross-sectional (16 subjects: 4 PD, 7 PSP, 5 controls)There were no differences in corneal sub-basal nerve density between the 3 groups.[31]
Arrigo et al. (2018)To describe corneal innervation and trigeminal alterations in drug-naive patients with PD.cross-sectional (15 subjects: 3 PD, 12 controls)Deep nerve tortuosity and the number of beadings were increased in patients with PD compared with controls.[53]
Daggumilli et al. (2019)To evaluate the progression of corneal endothelial changes in patients with PD on long-term oral amantadine therapy.1-year follow-up (150 subjects: 90 PD with amantadine, 30 PD naïve amantadine, 30 controls)SBNFLD was decreased in PD amantadine and PD amantadine naive group compared with controls after 1-year follow-up.[54]
  1. CCM corneal confocal microscopy, PD Parkinson’s disease, CNP corneal nerve parameters, IENFD intraepidermal nerve fiber density, CNFD corneal nerve fiber density, CNBD corneal nerve branch density, CNFL corneal nerve fiber length, UPDRS- III Unified Parkinson’s Disease Rating Scale III, SCOPA-AUT the scale for outcomes in Parkinson’s disease for autonomic symptoms, NCS nerve conduction studies, ACE-R Addenbrooke’s cognitive examination- revised, SBNFLD sub-basal nerve fiber layer density