Endoillumination during vitrectomy and phototoxicity thresholds
- FC Donders Institute of Ophthalmology, Department of Biomedical Engineering, and Institute of Dermatology, University Hospital Utrecht, Utrecht, Netherlands
- Dr P R van den Biesen, FC Donders Institute of Ophthalmology, University Hospital Utrecht, PO Box 85500, 3508 GA Utrecht, Netherlandsp.vdbiesen{at}oogh.azu.nl
- Accepted 26 May 2000
Abstract
AIM To assess the retinal phototoxicity hazards of and to provide safety margins for endoillumination during vitrectomy.
METHODS The absolute power and spectral distribution from various light sources and filter combinations that are commercially available for vitreous surgery were measured. The maximal exposure times based on the ICNIRP safety guidelines for photochemical and thermal injury of the aphakic eye were calculated. Additionally, the effect of various measures that reduce the risk of phototoxicity was evaluated.
RESULTS Measurements of the spectrum and energy indicated that the ICNIRP safety guidelines for photochemical retinal damage are exceeded within 1 minute for nine out of 10 combinations tested. With an additional 475 nm long pass filter, light levels below 10 mW, and a distance from light probe to retina of at least 10 mm, the allowable exposure time can be increased up to 13 minutes. Thermal damage can be anticipated when the light probe touches the retina.
CONCLUSION Commercially available light sources for endoillumination during vitrectomy are not safe with respect to photochemical retinal damage. Even with maximal precautions macular phototoxic damage remains a factual danger during vitrectomy.
