Increase in lens capsule stiffness caused by vital dyes

Abstract

Purpose: To assess potential changes in lens capsule mechanical properties after staining with brilliant blue, indocyanine green (ICG), and trypan blue.

Setting: Department of Ophthalmology and Applied Physics and Center for NanoScience, Ludwig-Maximilians-University, Munich, Germany.

Design: Experimental study.

Methods: Fifteen unstained lens capsules were dissected into 7 wedge-shaped parts. Three fragments were stained with brilliant blue 0.025%, ICG 0.05%, and trypan blue 0.06%, respectively, for 1 minute. Another 3 specimens were additionally illuminated using a standard light source. The seventh part served as an untreated control. All specimens were analyzed using atomic force microscopy (AFM) in contact mode with a scan rate of 0.6 Hz. Two scan regions of 10 μm × 10 μm were chosen, and stiffness was determined using AFM in a force spectroscopy mode. The force curves were performed with a data rate of 5000 Hz.

Results: Staining of the samples resulted in an increase in tissue stiffness (brilliant blue: P<.001; ICG: P<.01; trypan blue: P<.05). Additional illumination after staining further increased tissue stiffness, but not significantly. Mean increase in the relative elasticity values were 1.61 ± 0.15 (SD) for brilliant blue, 2.04 ± 0.21 for brilliant blue with illumination, 1.63 ± 0.22 for ICG, 2.01 ± 0.22 for ICG with illumination, 1.23 ± 0.11 for trypan blue, and 1.39 ± 0.11 for trypan blue with illumination. In relation to unstained tissue, the relative elasticity of the stained tissue increased 1.2-fold after illumination.

Conclusion: Staining significantly increased the mechanical properties of the human lens capsule.

Financial disclosure: No author has a financial or proprietary interest in any material or method mentioned.