• Ambient Light, IOL Choice, and the Circadian Clock

    By Lynda Seminara
    Selected and Reviewed By: Neil M. Bressler, MD, and Deputy Editors

    Journal Highlights

    JAMA Ophthalmology, August 2019

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    Chellappa et al. explored the effects of IOL choice on the functioning of the circadian system, cognitive function, and sleep regulation in older adults. They found that optimizing spectral light transmission in cataract surgery patients appears to minimize adverse age-related effects in all three areas.

    This cross-sectional study was performed at the Centre for Chrono­biology of the University of Basel and included 13 adults who had undergone cataract surgery (mean age, 69.9 years) and 16 healthy controls (mean age, 63.6 years). Eight of the cataract patients had received a blue-blocking (BB) IOL; the other five had received an IOL that blocked ultraviolet [UV] light only.

    The study consisted of 1) an ambu­latory segment lasting approximately three weeks, in which participants’ sleep-wake cycles were assessed, which was followed by 2) an in-laboratory segment.

    The in-lab portion began with 3.5 hours of dim-dark adaptation, immedi­ately followed by two hours of evening light exposure to either blue-enriched or non–blue-enriched light. This was followed by 30 minutes of dim light ex­posure, eight hours of sleep opportuni­ty, and two hours of morning dim light. This protocol was used three times for each patient, with one-week intervals between sessions.

    The authors analyzed salivary melatonin levels, cognitive test findings, sleep structure, and electroencepha­lographic activity to explore possible links between lens replacement and markers of circadian rhythms, cognitive performance, and sleep regulation.

    Compared with controls, patients with IOLs had an attenuated increase in melatonin levels during light exposure (mean increases: 23.3% in the BB group and 19.1% in the UV group; p < .001 vs. controls). Improvement in cognitive function, indexed by sustained atten­tion performance, was better for the UV-blocking IOL group (mean, 276.9 ms) than the BB IOL group (mean, 348.3 ms) during light exposure and after sleep.

    The increase in slow-wave sleep was higher for the UV group (mean increase, 13%) than for controls (mean increase, 5.2%). Frontal non-REM slow-wave activity during the sleep cycle was greater in the UV group than in the BB group (mean, 79.9 μV2/Hz vs. 53.2 μV2/Hz).

    These empirical data from stringently controlled lab conditions suggest that optimizing spectral light transmission in patients who undergo cataract sur­gery may have a beneficial effect on cir­cadian rhythms, cognition, and sleep. (Also see related commentary by Line Kessel, MD, PhD, FEBO, and Michael Larson, MD, DMSc, in the same issue.)

    The original article can be found here.