Investigating the Effect of Ionizing Radiation on Intraocular Lenses at Clinical Doses

Background: The natural crystalline lens of the eye is considered as one of the most radiosensitive tissues of the human body and long-time research demonstrates an association between ionizing radiation exposure and cataract development. Intraocular lens (IOL) implants are synthetic lenses used to replace the cataractous human lens of the eye and obtain optical rehabilitation in cataract surgery. However, post-operative complications such as capsular opacification, considerable cloudiness or discoloration may appear 2-3 years after the surgery. As the factors affecting the postoperative "life" of the IOL have not yet been fully clarified, in this study we examine if the irradiation with x-rays at clinical doses in interventional radiology and cardiology procedures of human eye can affect the transparency and clarity of the IOLs. Methods and findings: A number of intraocular lenses with different polymer composition and refractive power (diopters) were studied. In this work we present the results obtained with 3yellow azo-dye doped IOL (Alcon) and 1 undoped hydrophobic acrylic IOL (Alcon) having the same diopter, that were irradiated toclinical doses of 25, 67, 600 (for the doped) and 300 mGy (for the undoped IOL) respectively. The transmittance of the IOLs was measured pre-irradiation and post-irradiation by using a spectralon-coated integration sphere and a UV/Visible spectrometer over the visible-near infrared spectrum range from 420-900 nm. The transmission spectra of the IOL pre and post-irradiation indicate that in the blue-green spectrum region from 420-550 nm theIOLs show an increase in the transmittance T, with a highest ΔΤ changeequal to 35%, 37%, 38% at 420 nm for doses of 25 mGy, 67 mGy and 600 mGy respectively. In the residual spectrum region from 550-900 nm the transmittance is decreased by percentage 2%, 5% and 6%, respectively. However, the transmission spectrum of the undoped IOL presents the same behavior in the blue-green region and a change in the transmittance at percentage 4% is observed in the spectrum region 550-900 nm after x-ray irradiation to dose of 300 mGy. Conclusion: The results indicate that the irradiation with x-rays decreases the protection of the filter of the yellow azo-dye doped IOLs against the harmful for the retina UV radiation and short wavelength blue right, while affects slightly the transmittance in the residual visible-near infrared spectrum.