ABSTRACT
Objective:To observe the intrinsic association between cognitive function in patients with Parkinson′s disease (PD) and retinal structural changes in retina nerve fiber layer thickness, macular volume and macular thickness.Methods:A total of 36 patients with PD and 12 normal controls matched with age and sex were selected randomly. Examinations of Montreal Cognitive Assessment (MoCA), Mini-Mental State Examination (MMSE), Unified Parkinson′s Disease Rating Scale Ⅲ (UPDRS-Ⅲ), Hoehn-Yahr stage were performed in all subjects. The PD patients were divided into three groups according to the score of MoCA: PD without cognitive impairment (PD-NCI; n=12), PD with mild cognitive dysfunction (PD-MCI; n=13) and PD dementia (PDD; n=11). The retinal nerve fiber layer thickness, macular volume and thickness which were corrected with body mass index (BMI) were determined and analyzed by optical coherence tomography imaging. Results:The total RNFL thickness (μm/BMI) of the PD with cognitive impairment group (PD-MCI group: 3.55±0.12 ( t=2.552, P=0.014), PDD group: 3.07±0.18 ( t=4.122, P=0.000)) was thinner than that of the normal control group (4.05±0.16). The RNFL thickness in each quadrant of the PD with cognitive impairment group (PD-MCI group and PDD group) was thinner than those of the normal control group. The RNFL thickness gradually became thinner with the cognitive impairment increasing ( r=0.558 3, P<0.001). The macular volume (mm 3/BMI) of PD group (PD-NCI group: 0.274±0.010 ( t=2.523, P=0.015), PD-MCI group: 0.268±0.010 ( t=2.848, P=0.007), PDD group: 0.266±0.010 ( t=2.604, P=0.013)) was smaller than that in the normal control group (0.316±0.010), and the macular volume gradually decreased with the severity of cognitive impairment ( r=0.234 1, P=0.024). The macula thickness in each subgroup of PD was thinner than that of the normal control group. The macula thickness gradually became thinner with the cognitive impairment increasing ( r=0.283 9, P<0.001). The macular thickness (normal controls: (10.67±0.12) μm/BMI, PD group: (9.51±0.07) μm/BMI, t=8.312, P<0.001) and volume (normal controls: (0.316±0.010) mm 3/BMI, PD group: (0.270±0.010) mm 3/BMI, t=3.570, P<0.001) became thinner and smaller in patients with PD. Conclusions:In patients with PD, the thickness of the retina nerve fiber layer, the volume and thickness of the macula become thinner/smaller with the severity of cognitive impairments increasing. Macular thickness and volume in patients with PD appear thinner/smaller, which can be used as a valuable biological marker in the early stage of PD. The retina nerve fiber layer thickness in patients with PD becomes thinner, which may be accompanied by cognitive impairment.