Interaction between infrared radiation and vitreous substitutes
C. Azzolini, P. G. Gobbi, R. Brancato, L. Bosi, D. Gallo, M. Zelada and F. Patelli
Department of Ophthalmology and Visual Sciences, Scientific Institute H S. Raffaele, University of Milan, Milan, Italy.
OBJECTIVE: To characterize the interaction between midintrared radiation of
cutting lasers used or proposed for vitreoretinal surgery and fluid
vitreous substitutes commonly used in vitreoretinal surgery. METHODS:
Optical transmittance of vitreous substitutes was measured with a
double-beam spectrophotometer. Measurements were performed in a wide
spectral range of infrared radiation, including the 2120-nm wavelength of
the holmium-YAG laser and the water absorption peaks at 1440, 1930, and
2940 nm. RESULTS: The wavelengths considered have a penetration depth
varying from 410 to 1 microns in Ringer's solution, balanced salt
citrate-buffered solution, balanced salt bicarbonated-buffered solution,
hyaluronate sodium, and hydroxypropyl methylcellulose ophthalmic solution,
from 2000 to 13 mm in perfluorocarbon liquid, and from 52 to 2.5 mm in
silicone and fluorosilicone oils. CONCLUSIONS: Midinfrared optical
radiation exhibits dramatic differences of penetration depth in different
vitreous substitutes. High-absorbing liquids should be used mainly with
contact laser procedures and could provide a shield for remote structures.
Low-absorption vitreous substitutes allow noncontact laser surgical
procedures, but they also may cause direct optical damage to remote
tissues. The knowledge of wavelength transmittance of vitreous substitutes
is necessary to evaluate and optimize the efficacy and safety of cutting
laser sources.
