Free Radical Generation During Phacoemulsification Using Different Consoles

1. Free Radical Generation During Phacoemulsification Using Different Consoles Professor Steven D. Aust, PhD, Thomas Hebdon, Jordan Humbert, Scott Terry, Broc Gundersen Department of Chemistry and Biochemistry Utah State University Logan, Utah USA Research funded and travel expenses reimbursed by Alcon Laboratories No financial interest in the products discussed ASCRS 2009 April 3-8, San Francisco, CA

2. Study Purpose To quantitate hydroxyl radicals produced during phacoemulsification using various power modulations and ultrasonic modalities on two phacoemulsification platforms. The hydroxyl radical is a highly reactive free radical molecule that potentially creates oxidative stress in an ocular environment.

3. Background Studies References on free radical effects during phacoemulsification: Geffen N, Topaz M, Kredy-Farhan L, Barequet I, Farzam N, Assia E, Savion N. Phacoemulsification-induced injury in corneal endothelial cells mediated by apoptosis: In vitro model. J Cataract Refract Surg 2008; 34:2146-2152. Takahashi H, Sakamoto A, Takahashi R, Ohmura T, Shimmura S, Ohara K. Free radicals in phacoemulsification and aspiration procedures, Arch Ophthalmol 2002; 120:1348-1352. Previous Work: Cameron M, Poyer J, Aust S. The identification of free radicals produced during phacoemulsification. J Cataract Refract Surg 2001; 3:463-470 Aust S, Gardner J, Humbert J, Dimalanta R. Free radical generation as affected by different phacoemulsification technologies. Presented at: American Academy of Ophthalmology, November 9, 2008. Atlanta, GA.

4. Materials and Procedure Experiments were performed using two phacoemulsifier consoles: Alcon Infiniti Vision System Advanced Medical Optics (AMO, now Abbott) Sovereign Compact System All used their associated handpieces and tips The consoles and handpieces were operated between 0 and 100% power in 10% increments BSS flowing with continuous irrigation/aspiration at 28mL/min was sonicated, and aspirate was collected

5. Chemical Methodology Hydroxyl radical concentrations were estimated using the deoxyribose method with 5mM deoxyribose added to the irrigation solution (BSS) The concentration of malondialdehyde (MDA) in the aspirated irrigation solution was measured as a correlate to hydroxyl radical concentration Reference on methodology: Halliwell, B. and Gutteridge JMC. Hydroxyl Radicals Assayed by Aromatic Hydroxylation and Deoxyribose Degradation, Handbooks of Methods for Oxygen Radical Research (1985); 177-180, Greenwald R., CRC Press, Boca Raton Florida, 1985.

6. Peristaltic Pump Ultrasonic Tip Experimental Set-up BSS fluid containing 5mM deoxyribose flows from the irrigation bottle to the phacoemulsification handpiece where it is sonicated in a reaction vessel. On the Infiniti Vision System, the solution is aspirated with the system’s peristaltic pump from the reaction vessel and collected in the drain bag where a sample port has been added in the bottom of the bag to allow samples to be chronologically collected as it flows. The same is executed with the Sovereign Compact System, but solution is aspirated from the reaction vessel and collected from the tube exiting the peristaltic pump prior to the drain bag (not shown).

7. Degradation of Deoxyribose by the Hydroxyl Radical to form Malondialdehyde Deoxyribose Malondialdehyde Abstraction of a hydrogen atom from C4 of deoxyribose results in the formation of malondialdehyde (second compound after reaction 6) Cheeseman KH, Beavis A, Esterbauer H. Hydroxyl-radical-induced iron catalyzed degradation of 2-deoxyribose. Biochem J. 1988; 252:659-653.

8. Testing Configurations Studied Among Various Platforms, Power Modulations, and Modalities Continuous Longitudinal Ultrasound Infiniti Continuous 0.9 mm 30° Round Tip Sovereign Compact Continuous 20 Gauge 30° LAMINAR® Flow Phaco Tip Pulse-Modulated Longitudinal Ultrasound Using same tips as above for each platform and all at 33% duty cycle Infiniti Pulse Mode 6msec on, 12msec off Sovereign Compact WhiteStar C/F (6msec on, 12msec off) Mode Sovereign Compact WhiteStar C/F Mode with ICE (20% initial “punch”) Continuous Torsional Ultrasound Infiniti Torsional 0.9mm 45° Kelman® Mini Flared ABS® Tip

10. Conclusion Continuous Longitudinal Ultrasound On either platform using similar tip designs, continuous modes produced the highest concentrations of MDA Peak concentrations were about 40nM MDA at 90% power Between these two tests, higher concentrations were measured with Sovereign Compact at low power (<70%)

11. Conclusion Pulse Modulated Power Equivalent pulse modulation testing (about 33% duty-cycle) on either platform also gave similar results to each other and expectedly lower MDA concentrations compared to continuous U/S Sovereign Compact delivered higher concentrations at low power (<50%) Sovereign Compact W/S with ICE produced noticeably more MDA than without, likely because of the initial “punch” of power administered at each pulse

12. Conclusion Continuous Torsional Modality With its distinctly different motion as compared to traditional, longitudinal ultrasound, along with its design-specific tip, continuous torsional ultrasound produced the least amount of MDA among all other modes compared All data comparisons made are statistically significantly different (p<0.05 or better; data on file)