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Very Low Risk of Light-Induced Retinal Damage During Boston Keratoprosthesis Surgery: A Rabbit Study

Salvador-Culla, Borja MD; Behlau, Irmgard MD; Sayegh, Rony R. MD; Stacy, Rebecca C. MD, PhD; Dohlman, Claes H. MD, PhD; Delori, François PhD

doi: 10.1097/ICO.0000000000000029
Basic Investigation

Purpose: The aim of this study was to assess the possibility of light damage to the retina by a surgical microscope during implantation of a Boston Keratoprosthesis (B-KPro) in rabbits.

Methods: The retinal irradiance from a Zeiss OPMI Lumera S7 operating microscope was measured at the working distance (16.5 cm). Light transmittance through an isolated B-KPro was measured. A B-KPro was implanted into 1 eye of 12 rabbits with the optic covered during the procedure. The operated eyes were then continuously exposed to a fixed light intensity under the microscope for 1 hour. Fluorescein angiography was carried out on days 2 and 9 postsurgery, after which the animals were euthanized. Further, we compared the potential of these retinal exposures to well-accepted light safety guidelines applicable to humans.

Results: Light transmittance of B-KPro revealed a blockage of short wavelengths (<390 nm) and of long wavelengths (1660–1750 nm) of light. In addition, the surgical microscope filtered a part of the blue, ultraviolet, and infrared wavelengths. Neither fluorescein angiography nor a histological examination showed any morphological retinal changes in our rabbits. Moreover, the retinal exposures were well below the safety limits.

Conclusions: Modern surgical microscopes have filters incorporated in them that block the most damaging wavelengths of light. The B-KPro is made of 100% poly(methyl methacrylate), which makes it in itself a blocker of short wavelengths of light. No damage could be demonstrated in the animal study, and the retinal exposures were well below the safety limits. Together, these results suggest that light exposures during B-KPro surgery present a low risk of photochemical damage to the retina.

*Cornea Service, Massachusetts Eye and Ear Infirmary, Boston, MA;

Department of Ophthalmology, Harvard Medical School, Boston, MA;

Ophthalmic Pathology, Massachusetts Eye and Ear Infirmary, Boston, MA; and

§Schepens Eye Research Institute, Boston, MA.

Reprints: Borja Salvador-Culla, Massachusetts Eye and Ear Infirmary, 243 Charles St, Boston, MA 02114 (e-mail:

Supported by Keratoprosthesis Fund, Massachusetts Eye and Ear Infirmary, Boston, MA.

The authors have no conflicts of interest to disclose.

Received May 30, 2013

Accepted October 08, 2013

Copyright © 2014 Wolters Kluwer Health, Inc. All rights reserved.