Identification of free radicals produced during phacoemulsification

Purpose: To detect, identify, and quantitate free radicals produced during conditions similar to phacoemulsification cataract surgery. Setting: Research laboratory at the Biotechnology Center, Utah State Univer sity, Logan, Utah, USA. Methods: All experiments were performed using a Series Ten Thousand phacoem ulsifier (Alcon Laboratories) modified to make a 10 mt continuous circulati on loop eo increase sensitivity. The irrigating solution was passed through a 3 mt chamber in line with the circulation loop, and electron spin resona nce spin trapping methods were used to detect, identify, and quantitate fre e radical production during phacoemulsification. As an additional indicatio n of hydroxyl radical production, the hydroxylation of sailcylate and thioc yanate was detected by high-performance liquid chromatography and spectroph otometry, respectively. Results: The hydroxyl radical was formed when phacoemulsification was perfo rmed in the presence of solutions containing spin trap in double deionized water or balanced salt solution (BSS(R)). Hydroxyl radical production was l inear with respect to phacoemulsification time. Production of the hydroxyl radical was not observed when phacoemulsification was performed with anaero bic solutions, indicating a requirement for oxygen in radical production. T he concentration of trapped hydroxyl radical was reduced in the presence of balanced salt solution with bicarbonate, dextrose, and glutathione (BSS Pl us(R)). Upon phacoemulsification, both salicylate and thiocyanale underwent hydroxylation when included in the irrigating solution, confirming the gen eration of the hydroxyl radical, Additional tests discounted the formation of superoxide or hydrogen peroxide during phacoemulsification. Conclusions: Hydroxyl radical was produced by phacoemulsification in the pr esence of aerobic solutions, Hydroxyl radical production was dependent an t he presence of molecular oxygen and was not generated as a result of the ho molytic cleavage of water. The amount of hydroxyl radical detected was dire ctly proportional to phacoemulsification time and was reduced in the presen ce of BSS Plus. Other reactive oxygen species such as superoxide, hydrogen peroxide, and ozone were not detected during phacoemulsification under thes e conditions, (C) 2001 ASCRS and ESCRS.