So says a new study published in JAMA Ophthalmology.
In the study, over 2,500 patients with an average age at baseline of 73.5 years were followed over the course of 8 years. Along with their vision, the patients cognition was checked using the Mini-Mental State Exam at baseline, year 2, 6, and 8.

What did they find?
1. Patients that had worse vision at baseline also scored worse on the cognitive tests.
2. Vision and cognitive functioning are associated longitudinally (meaning they are changing together).
3. Vision has a substantially larger influence on subsequent change in cognitive score than the other way around.

How are vision and cognitive impairment related?
One theory is that worsening vision can discourage people from brain-stimulating activities like doing crosswords. Another theory is that “VA and cognitive function decline are both the result of a common cause, such as inflammation or degeneration of central nervous function”. (via)