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ORIGINAL RESEARCH |
From the Centre for Surgical Technologies the Department of Ophthalmology and the Department of Physics, Katholieke Universiteit Leuven, Leuven, Belgium; and the Division of Pediatric Surgery, Brown University School of Medicine, Providence, Rhode Island.
Address reprint requests to: François I. Luks, MD, PhD, Division of Pediatric Surgery, Brown University School of Medicine, 2 Dudley Street, Suite 180, Providence, RI 02905, E-mail: francois_luks{at}brown.edu
Objective: To evaluate light transmission, possible light trauma, and techniques for protection of the fetal eyes during intrauterine videoendoscopic surgery in a sheep model.
Methods: In vitro studies were done at various gestational ages, including spectrometry of light output by a halogen light source and telescope and light transmission by spectrophotometry in the range of 1803000 nm through amniotic fluid (AF) and fetal eyelids. In vivo electron-microscopic, morphologic analysis of the retinas of 65-, 95-, 108-, and 112-day-old fetal lambs with (n = 8) and without (n = 8) 30 minutes light exposure to the open eye was also done.
Results: The light spectrum at the tip of the telescope was 400750 nm, with a maximum irradiance of 3 x 10-3 W/cm2 at 580 nm. In the ultraviolet spectrum (less than 300 nm), irradiance was less than 0.5 x 10-3 W/cm2. Light transmission through ovine AF ranged from 30% at 300 nm to 89% at 700 nm at 84 days gestation, decreasing to less than 0.01% (300 nm) and 70% (700 nm) at 112 days. Fetal eyelids did not transmit more than 1% of light (any wavelength). After direct in vivo light exposure, no retinal damage was found. Photoreceptors were present from 108 days onward, but chromophores were scant or absent at all ages studied.
Conclusion: The light spectrum of a standard endoscope is limited to 400750 nm; ultraviolet light is filtered out. The AF transmits harmful blue light poorly. Fetal eyelids seem to protect the eye by extremely low transmission and light dispersion. Even with the eye open, no morphologic retinal damage was found. The strong light sources used with fetal endoscopy did not appear to pose a threat to the fetal retina.
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