Patients who received blue light-filtering intraocular lenses (BF-IOLs) following cataract surgery did not have a significant difference in the incidence rate of insomnia compared to patients who received non-BF-IOLs, according to a study published in the American Journal of Ophthalmology.
The study was designed to compare incidence of clinically diagnosed insomnia after cataract surgery in those with BF-IOLs and non-BF-IOLs. One concern has been that BF-IOLs interfere with the circadian rhythm, involved in the sleep-wake cycle, due to a long-term filtration effect of blue light from those IOLs that’s necessary to circadian photoentrainment.
“The circadian rhythm, entrained predominantly by light input, is mediated through retinal photoreceptors that partly project to the hypothalamus and regulate melatonin secretion by the pineal gland, with peak production at 464 nm of the light spectrum,” researchers explain. “Senile cataracts, clouding, and yellowing of the natural crystalline lens can affect the sleep-wake cycle through impaired light transmittance to the retina, particularly in the shorter blue light wavelength. Cataract surgery with intraocular lens (IOL) implantation improves ocular blue light transmission, which has been shown to have a beneficial effect on sleep patterns.”
The nationwide cohort study, with up to 10 years follow-up, used the Taiwan National Health Insurance Research Database (NHIRD), with the Taiwan Death Registry (TDR) providing secondary data analysis, of 171,415 patients who had cataract surgery in both eyes between 2008 and 2013, following them until 2018. A total of 19,604 (11.4%) and 151,811 (88.6%) patients had BF-IOL and non-BF-IOL implants, respectively, with the BF-IOL group tending to be younger with fewer chronic diseases.
Researchers used propensity score matching (PSM) to balance baseline characteristics between the 2 IOL groups and the Cox model and cause-specific hazard model to estimate hazard ratios (HR) and subdistribution hazard ratio (SHR).
They found that within a mean follow-up period of 6.2 years, incidence rates of insomnia (per 100 person-years) in the BF-IOL and non-BF-IOL groups were 2.97 and 3.21, respectively. There was no significant difference in the incidence rate of insomnia between the 2 IOL groups after treating all-cause mortality as a competing risk (SHR = 0.98, 95% CI = 0.95–1.01) and after PSM (HR = 0.97, 95%CI = 0.92–1.01), respectively, researchers report.
The study did have limitations, including not randomizing allocation to the IOL group: “We accounted for this by using PSM to control for significantly different variables between the 2 groups. However, some other confounders may still exist because these confounding variables, such as smoking, dietary intake, and sunlight exposure, were not available in the NHIRD.” Another limitation was that cataract surgery and insomnia were found using ICD codes from an administrative database provided by the single-payer National Health Insurance (NHI) program, which might have left out patients with mild sleep disturbances who didn’t seek care, or those coded inaccurately. “However, this nondifferential misclassification may have biased our results towards the null and diluted the real difference in insomnia incidence between these 2 IOL groups,” according to the study.
Finally, while the results were representational of the Taiwanese population, they might not apply to others, so further study in different settings is needed.
See LC, Li PR, Lin KK, Hou CH, Lee JS. Effect of blue light-filtering intraocular lenses on insomnia after cataract surgery: A nationwide cohort study with 10-year follow-up. Am J Ophthalmol. Published online February 3, 2022. doi:10.1016/j.ajo.2022.01.012