title: Influence of indocyanine green staining on the biomechanical strength of porcine internal limiting membrane.
abstract: OBJECTIVE
  Indocyanine green (ICG) has recently been introduced to stain selectively the internal limiting membrane (ILM) of the retina for ILM peeling. The aim of the present in vitro study was to examine the effect of ICG staining on the biomechanical properties of porcine ILM.
  
  
  METHODS
  Two parallel 10 x 7 mm strips of central retina were prepared from each of the 40 porcine eyes. 0.005% ICG staining combined with white light illumination for 3 min was performed. Unstained, nonilluminated and 0.1% glutaraldehyde-treated specimens were used as controls. Biomechanical-force elongation measurements were performed using an automated material tester. The absorption spectrum of the ICG solution and the emission spectrum of the light source was measured.
  
  
  RESULTS
  After ICG staining of the retina combined with 3 min of illumination, a significant increase in ultimate force by 45% and a decrease in ultimate elongation by 24% was found. Without light exposure, there was no such effect, suggesting a light-dependent process. After 30 min of 0.1% glutaraldehyde treatment, there was an increase in ultimate force by 107% and a decrease in ultimate elongation by 66.6%. The absorption spectrum of the light source was continuous in the range from 400 to 800 nm including the absorption peak of ICG at 700 nm.
  
  
  CONCLUSIONS
  ICG staining of the retina including the ILM causes a significant increase in the biomechanical stiffness thereby facilitating ILM peeling. The effect is due to a photosensitizing effect of ICG leading to collagen cross-linking.
authors.affiliation: Department of Ophthalmology, Universitätsklinikum CGC, Technical University of Dresden, Dresden, Germany. gwollens@homtail.com
authors.forename: Gregor
authors.initials: G
authors.lastname: Wollensak
authors.forename: Eberhard
authors.initials: E
authors.lastname: Spoerl
authors.forename: Christopher
authors.initials: C
authors.lastname: Wirbelauer
authors.forename: Duy-Thoai
authors.initials: DT
authors.lastname: Pham
mesh_terms: D000818:Animals; D001485:Basement Membrane / Q000187:drug effects; D004396:Coloring Agents / Q000494:pharmacology*; D004548:Elasticity / Q000187:drug effects*; D007208:Indocyanine Green / Q000494:pharmacology*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D012160:Retina / Q000187:drug effects*; D013194:Staining and Labeling; D013552:Swine; D013718:Tensile Strength / Q000187:drug effects*
chemical_list: D004396:Coloring Agents; D017319:Photosensitizing Agents; D007208:Indocyanine Green