Although cataract is associated with a decline in light transmission due to clouding and yellowing of the crystalline lens, it is unknown whether intraocular lens (IOL) replacement affects circadian rhythms, cognition, and sleep. A new study in JAMA Ophthalmology tested whether IOL replacement (blue light or ultraviolet only blocking) in patients with previous cataract is associated with beneficial light effects on these three factors.
The study was conducted from 2012-2014 at the Centre for Chronobiology, University of Basel, Switzerland, and included 16 healthy controls and 13 patients with previous cataract and IOL replacement. Patients were not given medication and did not have medical or sleep comorbidities.
To test the association, participants were given 3.5 hours of prior light control (dim-dark adaptation), followed by 2 hours of evening blue-enriched (6500 K) or non–blue-enriched (3000 K and 2500 K) light exposure, 30 minutes of dim post–light exposure, 8 hours of sleep, and 2 hours of morning dim light upon awakening. Participants were tracked using actigraphs to monitor sleep activity and given cognition tests in the morning.
Researchers found that those with previous cataract spent more time in deep sleep and performed better on cognitive tests than the control group. Those with blue light blocking lenses performed worse on cognitive tests than those with ultraviolet only blocking lenses.
Patients with cataract experienced less of a melatonin increase in response to the light controls, representing a “normalized” reaction typical of younger adults.
Chellappa SL, Bromundt V, Frey S, et al. Association of intraocular cataract lens replacement with circadian rhythms, cognitive function, and sleep in older adults [published online ahead of print May 2019]. Eye. doi:10.1001/jamaophthalmol.2019.1406.