title: Novel heavy tamponade for vitreoretinal surgery.
abstract: OBJECTIVE
  The aim of this study was to produce a heavy tamponade with a specific gravity greater than 1.06 g/mL that was optically transparent, could be manufactured using simple processing, could be injected using standard clinical equipment, and would have appropriate biocompatibility.
  
  
  METHODS
  Aerosil silica was added to a phenyl trimethicone and mixed via a roller, overhead stirring, and ultrasonics. The refractive index, visible absorbance, and shear viscosity were measured. The injectability of the solutions was evaluated using the Accurus Viscous Fluid Injection system. The tamponade efficiency was assessed using a model eye chamber and compared with that of Densiron 68, Oxane HD, and F6H8. The biocompatibility was evaluated in vitro and in vivo in rabbits.
  
  
  RESULTS
  Tamponade agents were produced with specific gravities of 1.10, 1.11, 1.13, and 1.16 g/mL that had good optical clarity. Mixing using overhead stirring was sufficient to produce tamponade agents with shear viscosities in the range 1000 to 5000 mPa·s that were reproducible and stable during storage. The solutions were easier to inject using the Accurus Viscous Fluid Injection system than silicone oil 1000 mPa·s. The 11% silica solution had greater tamponade efficiency than Densiron 68 or Oxane HD. There was no evidence of cytotoxicity in vitro. Silica solution 11% induced cataract earlier than Polydimethylsiloxane 1000 (PDMS 1000). Silica solution 11% and phenyl trimethicone reduced the a-wave value at 1 week after vitrectomy, but recovery was observed at later time points. Silica solution 11% caused inner nuclear layer (INL) nuclei dropdown in inferior retina from 4 weeks postoperation. Polydimethylsiloxane 1000 induced a similar phenomenon in superior retina 12 weeks postoperation.
  
  
  CONCLUSIONS
  We have produced a heavy tamponade with good clarity that has appropriate shear viscosity, injectibility, enhanced tamponade efficiency, and biocompatibility similar to that of PDMS 1000.
authors.affiliation: Department of Eye and Vision Science, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Williams
authors.forename: Victoria R
authors.initials: VR
authors.lastname: Kearns
authors.forename: Amy C
authors.initials: AC
authors.lastname: Lo
authors.forename: Michael
authors.initials: M
authors.lastname: Day
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Garvey
authors.forename: Yamini
authors.initials: Y
authors.lastname: Krishna
authors.forename: Da
authors.initials: D
authors.lastname: Ma
authors.forename: Theodor
authors.initials: T
authors.lastname: Stappler
authors.forename: David
authors.initials: D
authors.lastname: Wong
mesh_terms: D000818:Animals; D058450:Endotamponade / Q000379:methods*; D008422:Materials Testing / Q000379:methods; D023421:Models, Animal; D011817:Rabbits; D012822:Silicon Dioxide / Q000008:administration & dosage; D012827:Silicone Oils / Q000008:administration & dosage / Q000737:chemistry*; D013046:Specific Gravity; D013053:Spectrophotometry; D057586:Vitreoretinal Surgery / Q000379:methods*
chemical_list: D012827:Silicone Oils; D012822:Silicon Dioxide
keywords: biocompatibility; tamponade agent; viscosity