title: Visualizing hydrophobic domains in silicone hydrogel lenses with Sudan IV.
abstract: OBJECTIVE
  A lipophilic dye is used to investigate the degree to which the surface and bulk hydrophobic domains of the lenses can be imaged and to identify specific changes in the availability of those domains after in vitro wear and cleaning conditions. The effect of a multipurpose solution (MPS), OPTI-FREE RepleniSH, on lens hydrophobic domains was also investigated.
  
  
  METHODS
  Hydrophobic domains were determined using a saturated solution of Sudan IV. Staining periods of 30 minutes and 16 hours were used to determine surface versus bulk hydrophobic domains. Four types of silicone hydrogel lens materials were tested. The degree of staining was visually documented by photography and quantitatively determined by extraction and analysis of the total amount of dye adsorbed.
  
  
  RESULTS
  Specific differences in staining were found for all control lenses. Exposure to in vitro wear conditions significantly decreased the staining response for all lens types as compared with unworn lenses (P = 0.001). However, the trend of staining remained the same: balafilcon A > galyfilcon A > senofilcon A > lotrafilcon B. MPS decreased the extent of staining; the degree of its effect varied with lens type.
  
  
  CONCLUSIONS
  Hydrophobic staining with Sudan IV visualized domains on and within silicone hydrogel lenses. Differences in staining response after exposure to wear and cleaning conditions indicate the potential for protein and lipid deposition on the different lens types and the ability of MPS to affect that deposition. Hydrophobic staining may be useful for determining differences in surface modification and lipophilicity of silicone hydrogel lenses.
authors.affiliation: Department of Ophthalmology, LSU Eye Center, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70131, USA.
authors.forename: Jean T
authors.initials: JT
authors.lastname: Jacob
authors.forename: Jacques
authors.initials: J
authors.lastname: Levet
authors.forename: Tamika A
authors.initials: TA
authors.lastname: Edwards
authors.forename: Nissanke
authors.initials: N
authors.lastname: Dassanayake
authors.forename: Howard
authors.initials: H
authors.lastname: Ketelson
mesh_terms: D001391:Azo Compounds; D004396:Coloring Agents; D020100:Hydrogels / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D007910:Lenses, Intraocular; D012826:Silicone Elastomers / Q000737:chemistry*; D013194:Staining and Labeling / Q000379:methods
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D020100:Hydrogels; D012826:Silicone Elastomers; C009213:Scarlet Red