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Borja Salvador Culla, Irmgard Behlau, Rony R. Sayegh, François Delori, Claes H. Dohlman; Light-induced Maculopathy After Keratoprosthesis Surgery - True Or False?. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6065.
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To assess possible light damage to the retina by the surgical microscope during implantation of a Boston Keratoprosthesis (KPro) in rabbits.
A Zeiss ST-7 operating microscope was used. The theoretical retinal irradiance from the microscope was calculated from the measured irradiance at the working distance (16.5 cm). Also, light transmittance through an unused KPro was measured. A KPro was implanted into one eye of each of 10 Dutch-belted rabbits, by the same surgeon, with the optic of the KPro covered during the procedure to avoid any uncontrolled light exposure to the retina. Retinoscopy was performed right after implantation, and external additional lenses were used when needed, to focus the light on the retina. The operated eyes were then continuously exposed to a fixed light intensity under the microscope for 1 hour. After the exposure, the rabbits were monitored for 9 days and treated daily with both topical antibiotics and steroids. Fluorescein angiography (FA) was carried out at days 2 and 9, after which the animals were euthanized, the eyes enucleated and sent for histopathology.
FA showed no leak of dye or other morphological changes in any of our rabbits. Histological examination with H&E staining showed no morphological retinal changes in any of our cases. Light transmittance of the isolated KPro indicated blockage of short wavelengths (from 0.001% at 200nm to 42% at 390nm) and of long wavelengths (12-35% at the range of 1660-1750nm). In addition, the surgical microscope blocked part of the blue, ultraviolet (UV), and infrared (IR) wavelengths of the light spectrum.
Our results show that the PMMA of the Boston KPro has a low transmittance of phototoxic wavelengths of light. In addition, modern surgical microscopes have filters for UV and IR wavelengths of the light spectrum. No morphologic damage to the retina from the microscope light exposure could be demonstrated. Thus, there should be very low risk of light damage to the retina during routine KPro surgery.
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