Cognitive Level Enhancement through Vision Exams and Refraction (CLEVER): study protocol for a randomised controlled trial

Background: Longitudinal observational studies have found an association between vision impairment and accelerated decline in cognition. However, no randomised trials have assessed the possible benefit of vision correction on cognitive change. We present the protocol for a three-year randomised controlled trial designed to assess the impact of spectacles for distance and/or near vision correction on cognitive change among community-dwelling elderly participants in India.

Methods: Cognitive Level Enhancement through Vision Exams and Refraction (CLEVER) is a single-centre, open-label, parallel-group, individually-randomised trial. Participants (760 total, 380 in each arm) aged ≥ 60 years with correctable vision impairment at distance and/or near (presenting visual acuity < 6/18 in the better-seeing eye and improving to > = 6/18 with spectacles and/or presenting near vision worse than N6 at 40 cm and improving to N6 with spectacles), normal hearing (able to repeat at least three out of six words whispered from a 50 cm distance in the better ear) and normal cognition (Hindi Mini-mental Status Examination score > 18/31) will be enrolled. After a comprehensive eye examination, intervention group participants will receive distance, near, or bifocal spectacles, while controls will receive a prescription and spectacles at the end of the trial. The primary outcome will be the three-year change in Longitudinal Aging Study in India–Diagnostic Assessment of Dementia (LASI DAD) global cognitive factor score, with and without adjustment for baseline score, age, gender, education and other potential confounders.

Conclusion: CLEVER is designed to assess the effectiveness of spectacles as a low-cost intervention to prevent or delay cognitive decline.

Trial registration: This trial is registered with ClinicalTrials.gov, number NCT05458323, February 15, 2023.