Turkish researchers have found glaucoma patients, especially those with exfoliative glaucoma (XFG), have a diminished sense of smell.

Led by Dr Özlem Dikmetaş, Hacettepe University, the research team used the Sniffin’ Sticks smell test to assess odour threshold, discrimination and identification in 80 subjects. Of these, 20 patients had primary open-angle glaucoma (POAG), 20 had XFG, 20 had exfoliation syndrome (XFS) and 20 were age- and sex-matched healthy subjects with no evidence of ocular disease. While XFS and XFG patients showed reduced smell sensitivity compared with POAG patients and the healthy control group, the XFG group had a significantly lower smell identification level than any other group.

Researchers noted glaucoma’s many similarities to Alzheimer’s and Parkinson’s disease, where olfactory dysfunction is also common. In the case of Parkinson’s, the loss is typically evident four to eight years before diagnosis, but sometimes as early as 20 years prior. Although olfactory function naturally diminishes in the over-65s, the effect of neurodegenerative diseases and glaucoma on smell sensitivity may be an important indicator for early diagnosis, said researchers. Losing the sense of smell also impacts quality of life and personal safety, they added.