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Adam Elias Brondsted, Birgitte Haargaard, Birgit A Sander, Henrik Lund-Andersen, Poul Jennum, Steen Gammeltoft, Line Kessel; The effect of neutral and blue-blocking intraocular lenses on circadian photoentrainment. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4184.
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The intrinsically photosensitive retinal ganglion cells (ipRGCs) require blue light for the photoentrainment of the circadian rhythm. Blue light is absorbed by the cataractous lens and, to a lesser degree, by blue-blocking intraocular lenses (IOLs). The CIRCAT study is a randomized clinical trial aimed at evaluating the effect of cataract surgery and comparing the effect of blue-blocking and neutral IOLs on circadian photoentrainment. Data is presented from the interim analysis including 42 patients.
Patients with cataract and no other significant diseases were included and randomized to neutral or blue-blocking IOL implant. Examinations were performed before 2 days 3 weeks and 1 year after cataract surgery. Stimulation of ipRGC was determined by short wavelength chromatic pupillometry using the consensual postillumination pupil reaction (PIPR). The circadian rhythm was assessed by direct activity measurements (actigraphy) and by questionnaires (Pittsburg Sleep Quality Index & and Morningness Eveningness Questionnaire).
The PIPR increased significantly at 2 days (P=0.031) and 3 weeks (P=0.001) after surgery, but returned to baseline 1 year after (P=0.21). No effect of IOL type was found (P=0.53) Sleep efficiency measured with actigraphy did not change significantly in the neutral IOL group (P=0.13) but increased by 6.16 percentage points 1 year after surgery in the blue-blocking IOL group (P=0.012). The questionnaires revealed that IOL type affected the outcome at 1 year significantly (P=0.003 / P=0.021) leading to an increase in self-evaluated sleep quality (1.83 PSQI points) in the blue-blocking group and to a slight shift from “evening” to “morning type”.
We found that cataract surgery increased the PIPR to blue light suggesting an increased potential for circadian photoentrainment. However, 1 year after surgery the PIPR was back to preoperative levels. Adaptation in the circadian photoentrainment system may explain why the pupil reaction returns to baseline. Surprisingly, we also found an improvement in sleep quality associated with a relative shift in circadian type in the blue-blocking IOL treatment group. This suggests, that the adaptational mechanism is optimized for physiological lens yellowing and that the blue-blocking IOLs may protect the circadian photoetrianment system from inappropriately timed blue light (eg. television etc).
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