Visual complaints and visual hallucinations in Parkinson's disease

Background: Visual symptoms are common in Parkinson's disease (PD) and are frequently under-diagnosed. The detection of visual symptoms is important for differential diagnosis and patient management.

Aim: To establish the prevalence of recurrent visual complaints (RVC) and recurrent visual hallucinations (RVH) and to investigate their interaction in PD patients and controls.

Methods: This cross-sectional study included 88 PD patients and 90 controls. RVC and RVH were assessed with a visual symptom questionnaire and the North-East-Visual-Hallucinations-Interview (NEVHI).

Results: Double vision (PD vs.

Controls: 18.2% vs. 1.3%; p < 0.001), misjudging objects when walking (PD vs.

Controls: 12.5% vs. 1.3%; p < 0.01), words moving whilst reading (PD vs.

Controls: 17.0% vs. 1.3%; p < 0.001) and freezing in narrow spaces (PD vs.

Controls: 30.7% vs. 0%; p < 0.001) were almost exclusively found in PD patients. The same was true for recurrent complex visual hallucinations and illusions (PD vs.

Controls: both 17.0% vs. 0%; p < 0.001). Multiple RVC (43.2% vs. 15.8%) and multiple RVH (29.5% vs. 5.6%) were also more common in PD patients (both p < 0.001). RVC did not predict recurrent complex visual hallucinations; but double vision (p = 0.018, R(2) = 0.302) and misjudging objects (p = 0.002, R(2) = 0.302) predicted passage hallucinations. Misjudging objects also predicted the feeling of presence (p = 0.010, R(2) = 0.321).

Conclusions: Multiple and recurrent visual symptoms are common in PD. RVC emerged as risk factors predictive of the minor forms of hallucinations, but not recurrent complex visual hallucinations.