INTERACTION BETWEEN INFRARED RADIATION AND VITREOUS SUBSTITUTES

Objective: To characterize the interaction between midinfrared radiati on of cutting lasers used or proposed for vitreoretinal surgery and fl uid vitreous substitutes commonly used in vitreoretinal surgery. Metho ds: Optical transmittance of vitreous substitutes was measured with a double-beam spectrophotometer. Measurements were performed in a nide s pectral 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 d epth varying from 410 to 1 mu m in Ringer's solution, balanced salt ci trate-buffered solution, balanced salt bicarbonated-buffered solution, hyaluronate sodium, and hydroxypropyl methylcellulose ophthalmic solu tion, from 2000 to 13 mm in perfluorocarbon liquid, and from 52 to 2.5 mm in silicone and fluorosilicone oils. Conclusions: Midinfrared opti cal radiation exhibits dramatic differences of penetration depth in di fferent vitreous substitutes. High-absorbing liquids should be used ma inly with contact laser procedures and could provide a shield for remo te structures. Low-absorption vitreous substitutes allow noncontact la ser surgical procedures, but they also may cause direct optical damage to remote tissues. The knowledge of wavelength transmittance of vitre ous substitutes is necessary to evaluate and optimize the efficacy and safety of cutting laser sources.