Free Radical Generation During Phacoemulsification Using Different Consoles

1
Free Radical Generation During
Phacoemulsification Using Different Consoles
Department of Chemistry and Biochemistry Utah
State University Logan, Utah USA

• Professor Steven D. Aust, PhD,
• Thomas Hebdon, Jordan Humbert,
• Scott Terry, Broc Gundersen

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-i
  nduced injury in corneal endothelial cells
  mediated by apoptosis In vitro model. J
  Cataract Refract Surg 2008 342146-2152.
• Takahashi H, Sakamoto A, Takahashi R, Ohmura T,
  Shimmura S, Ohara K. Free radicals in
  phacoemulsification and aspiration procedures,
  Arch Ophthalmol 2002 1201348-1352.
• Previous Work
• Cameron M, Poyer J, Aust S. The identification of
  free radicals produced during phacoemulsification.
  J Cataract Refract Surg 2001 3463-470
• 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
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 systems 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
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
252659-653.
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

9
(No Transcript)
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
  (lt70)

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 (lt50)
• 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 (plt0.05 or better data
  on file)