A visual test based on images of faces and scenes could help doctors diagnose patients suffering from Alzheimer’s disease or other types of dementia, researchers said on Tuesday.

After giving patients groups of photos of scenes and faces and asking them to identify “the odd one out,” the scientists found Alzheimer’s patients have difficulty choosing the odd scene while sufferers with semantic dementia (SD), a disorder of language, had problems with faces.

Dr. Kim Graham, of the Medical Research Council Cognition and Brain Sciences Unit in Cambridge, England who headed the team, said an image test could be used along with standard memory evaluations to identify dementia patients.

“While further research is needed, facial and spatial tests such as ours could help in differentiating between the various forms of dementia,” Graham said.

Alzheimer’s, a progressive illness that eventually destroys memory and mental ability, is the leading cause of dementia in the elderly.

An estimated 12 million people worldwide have the illness and the numbers are expected to rise as the population ages. There is no cure but drugs can help some patients.

The scientists asked patients to select the odd image in 40 scene tests and an equal number of face tests. They also conducted MRI scans on the brains of the patients.

The findings, reported in the Journal of Neuroscience, support earlier research that suggested different areas in the medial temporal lobe of the brain could be responsible for various aspects of memory and perception.

Knowing which type of dementia patients suffer from is useful because the prognosis, types of problems they may encounter as the disease progresses and treatment can vary.

“Having an accurate diagnostic label is important for the individual and their family in terms of how they can plan for the future and for the clinicians in terms of decisions they will hopefully eventually be able to take in regards to drugs,” Graham added in an interview.

Rebecca Wood, chief executive of the Alzheimer’s Trust, which funded the study, said the research provides evidence of a link between visual perception and potential cognitive decline.

“We are delighted that this study has taken us a step closer to finding improved methods of diagnosing different forms of dementia,” she said in a statement.