title: The effect of tissue wrapping on the expansion of hydrophilic orbital implants.
abstract: OBJECTIVE
  Hydrogel implants have been used in hypoplastic orbital expansion. Advantages include insertion through a small incision and expansion without manipulation. The rapid rate of expansion, however, may lead to undesirable outcomes, including implant migration. The authors evaluate the effect of tissue wrapping on expansion of hydrogel implants.
  
  
  METHODS
  Three identical hydrogel implants were subjected to one of 3 in vitro interventions: unwrapped control, porcine scleral-wrapped, and porcine fascia-wrapped. Each implant was submerged in normal saline solution. Diameter and volume were measured hourly for 24 hours and then every 4 hours until a plateau or maximal weight was achieved. Measurements were plotted with time as the independent variable and the above measurements as dependent variables. In addition, the best exponential function was graphed and the area under the curve was calculated.
  
  
  RESULTS
  Linear plots of data showed a reduction in the rate of diameter and volume expansion for wrapped implants. The areas under the curve of the best-fit exponential function were less for both scleral- and fascia-wrapped implants. Fascia wrapping slowed the rate of volume expansion more than sclera. Also, fascia wrapping seemed to significantly reduce the final implant diameter and volume.
  
  
  CONCLUSIONS
  Tissue wrapping slows the rate of expansion of hydrogel spheres in vitro. Fascia wrapping may also reduce the final implant size.
authors.affiliation: Gavin Herbert Eye Institute, University of California, Irvine, CA, USA. Cnabavi@uci.edu
authors.forename: Cameron B
authors.initials: CB
authors.lastname: Nabavi
authors.forename: Erica
authors.initials: E
authors.lastname: Liu
authors.forename: Jeremiah P
authors.initials: JP
authors.lastname: Tao
mesh_terms: D000818:Animals; D019540:Area Under Curve; D020099:Coated Materials, Biocompatible / Q000008:administration & dosage*; D005205:Fascia; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000008:administration & dosage*; D020273:Orbital Implants / Q000592:standards; D011183:Postoperative Complications / Q000517:prevention & control; D019919:Prosthesis Implantation / Q000379:methods; D012590:Sclera; D013552:Swine
chemical_list: D020099:Coated Materials, Biocompatible; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate