Brian C'K' Au, M'D'

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• Brian C.K. Au, M.D.
• University of Arizona Department of
  Ophthalmology
• University of Texas Medical Branch Department
  of Ophthalmology
• ASCRS 2008 Annual Symposium Poster
• April 5-9, 2008

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Financial Disclosure

• Brian C.K. Au, M.D. and co-authors do not have
  financial interests in any ophthalmic products or
  proprieties mentioned henceforth in this
  presentation.
• Co-Authors (University of Arizona)
• Jason W. Friday, M.S. IV
• Stefano Lehman, M.D.
• Robert W. Snyder, M.D., Ph.D.
• Roxanna Ursea, M.D.

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Introduction

• Dislocation of the corneal donor button is a
  common post-operative complication and cause of
  decreased visual acuity in Descemets Stripping
  with Endothelial Keratoplasty (DSEK).
• Clinical Question Is there a tool or substance
  that can
• 1) Reduce the rate of donor button dislocation
  after DSEK?
• 2) Effectively accomplish 1 without intraocular
  toxicity?

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Purpose and Setting

• Purpose
• Part 1 To quantify the adhesive strength of
  Tisseel fibrin glue (Baxter, U.S.A.) when allowed
  to react in an in-vitro aqueous environment.
• Part 2 To determine whether Tisseel is toxic
  when injected into the anterior chamber using a
  rabbit model.
• Setting
• Experimentation and Analysis University
  Laboratory, University of Arizona Department of
  Ophthalmology Tucson, Arizona, USA.
• Creation of Virtual Poster University of Texas
  Medical Branch, Department of Ophthalmology and
  Visual Sciences Galveston, Texas, USA.

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Methods Part 1 Adhesive Strength

• The adhesive strength of Tisseel fibrin glue was
  tested by using a Penscale tension device (My
  Weigh, U.S.A.), which measures the amount of
  force required to displace a donor button from a
  native cornea. Five measurements were taken with
  no adhesive for control, then 10 measurements
  were taken following injection of Tisseel between
  the opposing corneal surfaces submerged in
  balanced salt solution (BSS).

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Methods Part 2 Intracameral Toxicity

• The toxicity of Tisseel was tested using five New
  Zealand white rabbits, where 0.05 mL of both the
  fibrin and thrombin components were injected into
  the anterior chamber. Rabbits were monitored and
  graded, on a scale of 0-10, for signs of toxicity
  post-operatively for seven days using a Panoptic
  ophthalmoscope and a Tono-pen.

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Methods Tension Device

• 10 donor 10 recipient New Zealand white rabbit
  clear corneas
• Donor corneas (epithelium Descemets stripped)
  adhered to concave glass lens by superglue
• Recipients corneas (epithelium Descemets
  stripped) adhered to convex epoxy lens by
  superglue
• System submerged in BSS
• Tisseel applied between donor and recipient
  corneal surfaces then surfaces apposed in-vitro
• After 5 minutes, tension applied and weight
  required to separate corneal surfaces was recorded

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Results

• Part 1 Adhesive Strength The average force
  required to dislocate the donor button with no
  adhesive was found to be negligible at zero
  Newtons (N). The average force required to
  displace a donor button adhered with Tisseel was
  0.15N (plt0.003).
• Part 2 Intracameral Toxicity The toxicity
  study showed only mild inflammation on
  post-operative day one (average grade of 1.8)
  which decreased to an average grade of 0.8 by day
  seven.

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Results Part 1 Adhesive Strength

• Table 1 Tension Device Readings. The initial
  weight of the glass lens with fixed recipient
  button, the weight at the moment of release, and
  the calculated difference yields the force of
  dislocation (F ma) against gravity (a
  9.8m/s2). Experimental groups were separated into
  those corneas previously submerged in BSS (Group
  1) and those that were used directly after
  preparation (Group 2).

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Results Part 2 Intracameral Toxicity

• Table 2. Rabbits were graded on 10 signs of
  inflammation using a Panoptic ophthalmoscope and
  a Tono-pen. Of note, rabbit 5 suffered a small
  puncture of the anterior capsule
  intraoperatively. While it was not removed from
  the experiment, this unintended trauma was taken
  into account when analyzing experimental results.

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Results (4)

• Rabbit 1 on post-operative day 7 graded as
  0/10.

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Conclusion

• Part 1 Adhesive Strength Tisseel fibrin
  adhesive reacts in an aqueous environment and
  provides ample force to prevent donor corneal
  button dislocation following DSEK in an in-vitro
  model.
• Part 2 Intracameral Toxicity Tisseel appears
  to be non-toxic when injected into anterior
  chambers of rabbits. Intracameral use of Tisseel
  may reduce the rate of donor button dislocation
  following DSEK.