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McCann et al. reported factors of the associations with intraocular pressure (IOP) and circumpapillary retinal nerve fibre layer (cRNFL) thickness (1). Increased IOP and reduced cRNFL were associated with increased age, myopic refractive error, male sex and hypertension. In addition, Alzheimer's disease was associated with thinner average global cRNFL, and Parkinson's disease (PD) and current smoking status were associated with thicker average global cRNFL, and I present recent information regarding their study in patients with PD.
Murueta-Goyena et al. reported the association between the changes of retinal thickness and their predictive value as biomarkers of disease progression in idiopathic PD (2). The authors used macular ganglion-inner plexiform layer complex (mGCIPL) and peripapillary retinal nerve fiber layer (pRNFL) thickness reduction rates, and the Montreal Cognitive Assessment (MoCA) questionnaire was also applied. The adjusted relative risks of lower parafoveal mGCIPL and pRNFL thickness at baseline for an increased risk of cognitive decline at 3 years significantly increased. This means that reduced retinal thickness is a risk factor of cognitive impairment in patients with PD. McCann et al. did not evaluate cRNFL in PD patients with cognitive impairment, and I suppose that progression of cognitive impairment in patients with PD might accelerate reduction of average global cRNFL.
Second, Sung et al. also investigated the association be...
Second, Sung et al. also investigated the association between retinal thinning and cognitive impairment in patients with PD (3). There were significant reductions in the thickness of average, temporal, and inferior pRNFL and overall mGCIPL in patients with PD, and the MoCA score was significantly associated with mGCIPL thinning. As the thinning of the mGCIPL was also significantly associated with the volumetric parameters of some brain structures, the relationship between retinal thickness and brain structures in patients with PD should be comprehensively evaluated with special reference to the level of cognitive impairment.
Finally, Matlach et al. reported that thinning of some retinal layers of the ipsilateral eye was observed in the most-affected body side of PD patients (4). In addition, thickness of pRNFL and mGCIPL did not correlate to the severity of PD. As Murueta-Goyena et al. reported that there was no significant association between retinal thickness and motor deterioration (2), the discrepancy in the relationship of cognitive decline and motor deterioration with retinal thickness might be related to the lack of relationship between retinal thickness and the severity of PD.
1. McCann P, Hogg R, Wright DM, et al. Intraocular pressure and circumpapillary retinal nerve fibre layer thickness in the Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA): distributions and associations. Br J Ophthalmol. 2020 Jul 30 doi: 10.1136/bjophthalmol-2020-316499 [Epub ahead of print]
2. Murueta-Goyena A, Del Pino R, Galdós M, et al. Retinal thickness predicts the risk of cognitive decline in Parkinson's disease. Ann Neurol 2020 Oct 24 doi: 10.1002/ana.25944 [Epub ahead of print]
3. Sung MS, Choi SM, Kim J, et al. Inner retinal thinning as a biomarker for cognitive impairment in de novo Parkinson's disease. Sci Rep 2019;9:11832.
4. Matlach J, Wagner M, Malzahn U, et al. Retinal changes in Parkinson's disease and glaucoma. Parkinsonism Relat Disord 2018 Nov;56:41-46.