“All three of these diseases affect aging populations and involve selective loss of certain populations of neurons,” said Dr. Neeru Gupta, a professor of ophthalmology and director of the glaucoma unit at the University of Toronto. “Parkinson’s affects motor control. Alzheimer’s affects cognition. Glaucoma disrupts vision. But the closer we look, the more they seem to have in common.”
Even the official definition of glaucoma, a disease that accounts for more than eight million cases of blindness worldwide, has changed. Today, diagnosis is based on just two features: visible damage to the optic nerve, which leads from the retina at the back of the eye to the brain, and loss of peripheral vision, which can be measured by a simple test in an eye doctor’s office.
“Intraocular pressure is nowhere to be found in the definition, which shows you how the field has changed,” said Dr. Stuart McKinnon, an associate professor of ophthalmology and neurobiology at Duke University School of Medicine.
Researchers still recognize high pressure within the eye as a leading risk factor for glaucoma. And ophthalmologists still use the familiar screening test that shoots a puff of air at the front of the eye to measure pressure and screen for the disease. But since about 30 percent of people with the disease have normal or low pressure, there’s obviously something else at work.