How to reduce free radicals during phacoemulsification - EPR measurements comparing the production of free radicals in different use cases.

Purpose: To detect free radicals during phacoemulsification in different use cases and with emulsification of lens tissue.

Setting: Institute for Interfacial Engineering and Biotechnology, Fraunhofer Institute, Stuttgart, Germany.

Design: Experimental study.

Methods: Three experimental setups were used: 1. Setup without running fluidics to produce air bubbles inside the system. 2. Circulation fluidic setup to compare measurements with and without cataractous lens material. 3. A surgery-comparable system that closely mimics a realistic setup.Porcine lenses were incubated for 1.25h in formalin to simulate middle hard cataracts and emulsified in a test chamber. Free radicals were captured by the spin-trapping agent 5,5'-dimethyl-1-pyrroline N-oxide and measured using electron-paramagnetic resonance spectroscopy.

Results: Hydroxyl-radicals were the predominant free radicals detected. The maximum amount of radicals was produced when air bubbles were allowed to build up inside the system. Less radicals were produced during lens-emulsified compared to application without lens. This effect was enhanced when the phacotip was in close contact with the lens during the whole procedure. In the surgery-comparable setup, the least amount of free radicals was detected.

Conclusion: For the first time we were able to analyze free radicals during phacoemulsification of lens-tissue. We show that emulsification of lens tissue reduces the production of free radicals, an effect that is enhanced during close contact of the tissue with the phacotip. Also, we show that air-bubbles should be avoided during cataract surgery, as they may enhance free radical production. Furthermore, running fluidics remove most of the radicals making oxidative stress less likely.