Influence of indocyanine green staining on the biomechanical properties of porcine anterior lens capsule.
OBJECTIVE
Indocyanine green (ICG) has recently been introduced in cataract surgery to stain the anterior lens capsule for better visualization of the capsulorhexis. The aim of the current in vitro study was to examine the effect of ICG staining on the biomechanical strength of the anterior porcine lens capsule.


METHODS
Two parallel, 8 mm anterior lens capsule strips were prepared from each of 65 porcine postmortem eyes. ICG staining combined with white light exposure of 0.5, 1, 3, and 30 min duration was conducted. Unstained, nonilluminated and 0.1% glutaraldehyde-treated specimens were used as controls. Biomechanical stress-strain measurements were performed using an automated material tester. The absorption spectrum of the 0.5% ICG solution and the emission spectrum of the light source were controlled.


RESULTS
After ICG staining combined with at least 3 min light exposure, a significant increase of stress (31%) at 25% strain and a significant decrease (7%) in ultimate strain 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 a similar increase in stress (322%) at 25% strain and a decrease (47.6%) in ultimate strain.


CONCLUSIONS
ICG staining of the lens capsule causes a significant increase in elastic stiffness and a reduction in ultimate extensibility, thereby facilitating a smooth continuous capsulorhexis. The effect is due to a photosensitizing effect of ICG, leading to collagen cross-linking.
Wollensak
Gregor
G
Department of Ophthalmology, Universitätsklinikum CGC, Technical University of Dresden, Dresden, Germany. gwollens@hotmail.com
Spoerl
Eberhard
E
D000818:Animals; D003094:Collagen / Q000378:metabolism*; D004396:Coloring Agents / Q000494:pharmacology*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004548:Elasticity / Q000187:drug effects* / Q000528:radiation effects; D007208:Indocyanine Green / Q000494:pharmacology*; D007903:Lens Capsule, Crystalline / Q000502:physiology* / Q000528:radiation effects*; D017319:Photosensitizing Agents / Q000494:pharmacology; D013194:Staining and Labeling / Q000379:methods; D013552:Swine; D013718:Tensile Strength / Q000187:drug effects* / Q000528:radiation effects
D004396:Coloring Agents; D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D007208:Indocyanine Green