Safety of cornea and iris in ocular surgery with 355-nm lasers

Abstract

Abstract. A recent study showed that 355-nm nanosecond lasers cut cornea with similar precision to infrared femtosecond lasers. However, use of ultraviolet wavelength requires precise assessment of ocular safety to determine the range of possible ophthalmic applications. In this study, the 355-nm nanosecond laser was evaluated for corneal and iris damage in rabbit, porcine, and human donor eyes as determined by minimum visible lesion (MVL) observation, live/dead staining of the endothelium, and apoptosis assay. Single-pulse damage to the iris was evaluated on porcine eyes using live/dead staining. In live rabbits, the cumulative median effective dose (ED 50 ) for corneal damage was 231 J∕cm 2 , as seen by lesion observation. Appearance of endothelial damage in live/dead staining or apoptosis occurred at higher radiant exposure of 287 J∕cm 2 . On enucleated rabbit and porcine corneas, ED 50 was 87 and 52 J∕cm 2 , respectively, by MVL, and 241 and 160 J∕cm 2 for endothelial damage. In human eyes, ED 50 for MVL was 110 J∕cm 2 and endothelial damage at 453 J∕cm 2 . Single-pulse iris damage occurred at ED 50 of 208 mJ∕cm 2 . These values determine the energy permitted for surgical patterns and can guide development of ophthalmic laser systems. Lower damage threshold in corneas of enucleated eyes versus live rabbits is noted for future safety evaluation. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Correction of hyperopia by intrastromal cutting and liquid filler injection

“…[32][33][34][35][36] Patient safety is likely not a concern when a UV-A wavelength of 355 nm is used for intrastromal cutting because the threshold for photodamage at this wavelength is four orders of magnitude higher than for UV-B wavelengths around 250 nm, and the total energy required for dissection remains well below damage thresholds for photokeratitis. 33,34,37 However, it should be emphasized that the use of laser light at 355 nm is not essential for the feasibility of the method. IR fs pulses at 1040 nm, as commonly used in Femto-LASIK, could also be applied.…”