Primary vision and facial emotion recognition in early Parkinson's disease

Background: In early stages of idiopathic Parkinson's disease (IPD), lower order vision (LOV) deficits including reduced colour and contrast discrimination have been consistently reported. Data are less conclusive concerning higher order vision (HOV) deficits, especially for facial emotion recognition (FER). However, a link between both visual levels has been hypothesized.
Objective: To screen for both levels of visual impairment in early IPD.
Methods: We prospectively recruited 28 IPD patients with disease duration of 1.4 +/− 0.8 years and 25 healthy controls. LOV was evaluated by Farnsworth-Munsell 100 Hue Test, Vis-Tech and Pelli-Robson test. HOV was examined by the Ekman 60 Faces Test and part A of the Visual Object and Space recognition test.
Results: IPD patients performed worse than controls on almost all LOV tests. The most prominent difference was seen for contrast perception at the lowest spatial frequency (p = 0.0002). Concerning FER IPD patients showed reduced recognition of “sadness” (p = 0.01). “Fear” perception was correlated with perception of low contrast sensitivity in IPD patients within the lowest performance quartile. Controls showed a much stronger link between “fear” perception” and low contrast detection.
Conclusion: At the early IPD stage there are marked deficits of LOV performances, while HOV performances are still intact, with the exception of reduced recognition of “sadness”. At this stage, IPD patients seem still to compensate the deficient input of low contrast sensitivity, known to be pivotal for appreciation of negative facial emotions and confirmed as such for healthy controls in this study.