While the downstream effects of the aging lens—most often in the form of cataracts—include long-term disruption of circadian rhythm, cognitive function and sleep regulation, little is known about the impact of intraocular lens (IOL) implantation on these functions. However, researchers recently found that improving vision with an IOL post-cataract surgery may minimize these adverse age-related effects. 

This cross-sectional study included 16 healthy older controls and 13 patients with previous cataract and IOL replacement—five had ultraviolet (UV) IOLs and eight had blue-blocking (BB) IOLs—who were not taking medication and did not have medical or sleep comorbidities. The participants were exposed to three and a half hours of light control (dim-dark adaptation), followed by two hours of evening blue-enriched (6500K) or non-blue-enriched light (3000K and 2500K), 30 minutes in dim post-light, eight hours of sleep opportunity and two hours of morning dim light following sleep. 

The team assessed salivary melatonin, cognitive test results and sleep structure and electroencephalographic activity to test the association of IOLs with markers of circadian rhythm regulation, cognitive performance and sleep regulation, respectively.

They found that patients with IOLs had an attenuated increase in melatonin levels during light exposure (mean increase in the BB group: 23.3% and in the UV group: 19.1%) compared with controls (mean increase: 48.8%). They note that cognitive function, indexed by sustained attention performance, improved in patients with UV lenses compared with patients with BB lenses during light exposure and in the morning. The study authors add that patients with UV IOLs had increased slow-wave sleep (mean increase: 13%) compared with controls (mean increase: 5.2%) and frontal, non-rapid eye movement slow-wave activity during the first sleep cycle compared with patients with BB IOLs.