J. Griepentrog1, X. Zhang1, O. Marroquin3, J. Chang3, N. Loewen2, M. Rosengart1 1University Of Pittsburgh,Surgery,Pittsburgh, PA, USA 2University Of Pittsburgh,Ophthalmology,Pittsburgh, PA, USA 3University Of Pittsburgh,Medicine,Pittsburgh, PA, USA
Introduction: During the process of aging, the lens undergoes progressive changes that perturb the transmission of light, particularly the short-wavelength (400-500nm) blue spectrum. It is this shorter wavelength that maximally entrains our circadian rhythms, which orchestrate adaptive alterations in physiology, metabolism, and immunity. Several recent studies highlight that cataract surgery is associated with a reduced risk of all-cause mortality. Intraocular lenses (IOL) differ in transmission properties: conventional (Natural-IOL) and blue-light filtering (Blue-IOL). We hypothesized that in patients undergoing bilateral cataract surgery, the restoration of exposure to blue light with the implantation of Natural-IOL compared to continued blockage with Blue-IOL is associated with a reduced risk of death.
Methods: We conducted a retrospective cohort analysis of all subjects undergoing bilateral cataract surgery within a single healthcare system. We abstracted data for each subject regarding age, sex, race, zip code and state of residence, health insurance status, smoking status, alcohol use, and body mass index. Systemic comorbidities were classified using the Charlson Comorbidity Index. The primary outcome was all-cause mortality. We conducted a multivariate Cox Proportional Hazards model, stratified by and clustered on surgeon, to compare the adjusted risk of death in subjects undergoing bilateral implantation of Blue-IOL with those receiving Natural-IOL. A p<0.05 was considered significant. Sensitivity analyses for mortality were performed 1) using a more restrictive definition of ‘concomitant’ bilateral cataract surgery (<90-day interval), 2) excluding any surgeon implanting predominantly (>90%) Blue-IOL, and 3) restricting the analysis to Pennsylvania (PA) residents.
Results: A total of 1482 subjects underwent bilateral cataract surgery during the period of analysis, of which 512 (34.6%) received a Blue-IOL. Natural-IOL were associated with a reduced risk of all-cause mortality: aHR, 0.60 [95% CI, 0.38 to 0.94]; p=0.03. There was a significant difference by age category (p=0.02 for interaction with age >65): for the subgroup >65, Natural-IOL were associated with reduced mortality: aHR 0.52 [95% CI, 0.35 to 0.78]; p=0.001. Restricting bilateral surgery to a 90-day interval (n=1163), eliminating the surgeon implanting predominantly Blue-IOL (n=1133), and restricting the analysis to PA residents (n=1463), each showed that Natural-IOL are associated with prolonged survival.
Conclusion: Among patients undergoing cataract surgery, restoring the transmission of the entire visible spectrum compared to blocking the shorter wavelength blue spectrum, is associated with a reduced risk of death. These data suggest that a progressive blockage of blue light by cataracts may perturb circadian biology, and that cataract surgery that restores the shorter wavelength of visible blue light may restore these homeostatic mechanisms.