Objective: To develop a sensitive web-based test to detect visuo-perceptual deficits in patients with Parkinson’s disease as an early marker of dementia.

Background: Up to half of all patients with Parkinson’s disease (PD) will develop dementia within ten years. Early detection of dementia will allow initiation of treatment and enrichment for clinical trials, but there are no robust clinical markers of early dementia. Converging evidence shows that patients with disease affecting visual processing brain regions are at highest risk of rapid dementia in PD. However current tests of visuo-perceptual function are poorly sensitive and non-quantitative. We present a sensitive and quantitative test of visuo-perceptual function for early detection of dementia in PD, based on identification of skewed images of cats and dogs that can be delivered via a web-based platform.

Methods: Participants accessed the online testing site that collected demographic and PD-specific information. Visual acuity was measured using an online psychometric procedure. Cat and dog stimuli were converted to grayscale, added to a proportion of visual noise and skewed along the x-axis, using an affine matrix transformation. 3 levels of skew were used, based on pilot testing.

On each trial, participants indicated if the image they had seen was a cat or a dog by pressing one of two keys. Performance at each level of skew was compared using a repeated measures ANOVA. The test was validated in a face-to-face clinical cohort using approved scales (MDS-UPDRS, visual acuity, detailed neuropsychology).

Results: A total of 56 patients with PD and 283 people without PD accessed the online website. People younger than 40 were excluded, leaving a total of 247 age-matched controls. Patients with PD were worse at identifying skewed images than age-matched controls, F=3.71, p=0.025. Performance in the Cats and Dogs Test correlated with other cognitive measures in a face-to-face cohort without dementia (R2=0.33, p=0.00043) indicating that this is a robust measure.

Conclusions: Patients with PD were worse at the online Cats and Dogs test than age-matched controls.

We propose that this new Cats and Dogs test may be useful to detect the earliest stages of dementia in PD. Its delivery within an online platform makes it a useful tool for collaboration.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-cats-dogs-test-a-web-based-platform-to-detect-early-visual-processing-deficits-in-parkinsons-disease/