The use of ultrasound (US) probes in the emulsification andremoval of cataracts has the side effect of corneal and scleralburning. In order to quantify the effects of burning on thesetissues, experiments were conducted using bovine corneas todetermine the activation energy (E) and frequency factor (A)from an Arrhenius damage model. Bovine corneas were heatedon a constant temperature copper stage set at the desiredtemperature (ranging between 40-70°C). The damage criterionset was the loss of transparency of the tissue and the timerequired to reach the opacity was used to construct an Arrheniusinjury model. Results yielded an activation energy of 98.56kJ/mole and a frequency factor of 2 9 x 1013s-1. Afterdetermining the parameters for the Arrhenius damage integral,a numerical model was developed to simulate the damage basedon variations of the temperature at the ultrasound probe tipwith time. Results indicate that as much as 39% of the cornea(in area) can be damaged irreversibly (Q>1) for temperaturesreaching 65°C for a time period of 3 minutes. An intermittentprocedure which does not allow temperatures to reach beyond60°C for more than a minute was found to be optimal fortreatment purposes. These results show that the sensitivity ofthe corneal tissue during US heating can be quantitativelymeasured and predicted. It is therefore important to optimizethe treatment procedure to minimize thermal injury during theprocedure.
|Original language||English (US)|
|Title of host publication||Advances in Heat and Mass Transfer in Biotechnology|
|Publisher||American Society of Mechanical Engineers (ASME)|
|Number of pages||2|
|State||Published - 2000|
|Event||ASME 2000 International Mechanical Engineering Congress and Exposition, IMECE 2000 - Orlando, United States|
Duration: Nov 5 2000 → Nov 10 2000
|Name||ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)|
|Conference||ASME 2000 International Mechanical Engineering Congress and Exposition, IMECE 2000|
|Period||11/5/00 → 11/10/00|
Bibliographical noteFunding Information:
The authors would like to thank Prof. J.D. Humphrey for his many insightful comments and Mr. B. Tippett who aided in the tests of the balloon heating rates. The authors are also grateful for the support of the Boston Scientific Corporation, Inc. and the Whitaker Foundation.
© 2000 American Society of Mechanical Engineers (ASME). All rights reserved.