Researchers in Australia have developed new visual tests that could help detect early signs of dementia associated with Parkinson's disease, potentially enabling earlier diagnosis.

The researchers at Australia's University of Queensland (UQ) led the development of the tests to detect early signs of dementia in Lewy body disease, which includes Parkinson's disease and dementia with Lewy bodies, according to a UQ statement released on Wednesday.

Lewy body disease is the second most common form of degenerative dementia and occurs when Lewy bodies, abnormal clumps of a protein called alpha-synuclein, build up in the brain's nerve cells and interfere with how they work.

Difficulty processing visual information is an early feature of Lewy body disease and can appear before other obvious symptoms, said neurologist Professor Peter Nestor from UQ's Queensland Brain Institute, who led the development of the tests.

The researchers examined two visual pathways: one involved in recognizing what we are looking at, and the other in processing where something is located.

The study, published in the Journal of Neurology, examined visual processing across the full spectrum of Lewy body disease, including in people with Parkinson's disease who were not experiencing any cognitive symptoms, as well as people with Alzheimer's disease.

Results showed that visual problems were worse for those with Lewy body disease than Alzheimer's disease, with the two conditions affecting visual processing pathways differently. Visual hallucinations, a common symptom of Lewy body disease, were also closely linked to visual processing difficulties, the study showed.

Nestor said the new tests can detect the very earliest signs of emerging dementia in Lewy body disease, including in some people with Parkinson's disease who were not yet aware of their visual processing difficulties.