Experiencing changes in the visual system such as an inability to perceive colours may act as important biomarkers for the early detection and monitoring of Parkinson's disease, according to a new study.

"Just as the eye is a window into the body, the visual system is a window into brain disorders," said lead researcher Alessandro Arrigo, from the Vita-Salute San Raffaele University in Italy.Parkinson's disease is a neurodegenerative condition caused by neuronal loss in several brain structures and is characterised by tremors, rigidity or stiffness throughout the body, and impaired balance and coordination."Although Parkinson's disease is primarily considered a motor disorder, several studies have shown that non-motor symptoms are common across all stages of the disease. However, these symptoms are often undiagnosed because patients are unaware of the link to the disease and, as a result, they may be under-treated," Arrigo said. 

Non-motor symptoms, including visual alterations such as an inability to perceive colours, a change in visual acuity, and a decrease in blinking which can lead to dry eye, may precede the appearance of motor signs by more than a decade, Arrigo said.The study, published online in the journal Radiology, also revealed significant abnormalities within the visual system brain structures of Parkinson's disease patients, including alterations of optic radiations, a reduction of white matter concentration and a reduction of optic chiasm volume.