Background issues

New research suggests there is a 55% increased risk of cognitive impairment among people with poor vision.  This has global implications, as the number of people living with dementia worldwide will rise from 50 million in 2017 to 131.5 million by 2050. In India alone, the total cost for dementia care will soon consume 0.5% of its Gross Domestic Product.  Near and distance refractive errors account for over half of global vision impairment, and are demonstrated by published, population-based studies to affect some 80% of our proposed target population. Safely and inexpensively corrected with glasses, refractive errors are the most common and easily treated cause of vision loss. Despite considerable longitudinal observational evidence, there have been no randomised trials to investigate whether providing near and distance glasses can slow cognitive decline in the elderly.

Trial design

CLEVER (Cognitive Level Enhancement through Vision Exams and Refraction) is a randomised controlled trial designed to assess the impact and cost-effectiveness of glasses on cognitive decline and quality of life among the elderly in India. CLEVER will recruit 760 people from peri-urban/rural areas of Hyderabad, India. All participants will be aged 60 or over with poor distance or near vision due to uncorrected or under-corrected refractive error.  The participants and will be randomly divided into an intervention group and a control group.  People in the intervention group will receive glasses at the beginning of the trial. People in the control group will receive free glasses at the end of the trial if they need them.


Three-year change in cognition measured by LASI-DAD global cognitive score.

CLEVER aims to provide proof of a causative association between vision correction and the slowing of cognitive decline. A positive trial outcome will unlock investment in inexpensive vision care for the elderly.


36 months, with primary and secondary outcomes collected every 12 months. Identifier: NCT05458323