Purpose: 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 × 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.

Keywords:
Indocyanine green, Biomechanics, Cross-linking, Photodynamic effect, Internal limiting membrane
1.
Kadonosono K, Itoh N, Uchio E, Makamura S, Ohno S: Staining of the internal limiting membrane in macular hole surgery. Arch Ophthalmol 2000;118:1116–1118.
2.
Gandorfer A, Messmer EM, Ulbig MW, Kampik A: Indocyanine green selectively stains the internal limiting membrane. Am J Ophthalmol 2001;131:387–388.
3.
Kampik A, Sternberg P: Indocyanine green in vitreomacular surgery – (why) is it a problem? Am J Ophthalmol 2003;136:527–529.
4.
Kwok AKH, Li WWY, Pang CP, Lai TYY, Yam GHF, Chan NR, Lam DSC: Indocyanine green staining and removal of internal limiting membrane in macular hole surgery: Histology and outcome. Am J Ophthalmol 2001;132:178–183.
5.
Tadayoni R, Paques M, Girmens JF, Massin P, Gaudric A: Persistence of fundus fluorescence after use of indocyanine green for macular surgery. Ophthalmology 2003;110:604–608.
6.
Gandorfer A, Haritoglou C, Gandorfer A, Kampik A: Retinal damage from indocyanine green in experimental macular surgery. Invest Ophthalmol Vis Sci 2003;44:316–323.
7.
Costa RA, Farah ME, Freymüller E, Morales PH, Smith R, Cardillo J: Choriocapillaris photodynamic therapy using indocyanine green. Am J Ophthalmol 2002;132:557–565.
8.
Ieki Y, Nishiwaki H, Miura S, Hirata Y, Sakata I, Nonaka A, Kiryu J, Honda Y: Quantitative evaluation for blood-retinal barrier breakdown in experimental retinal vein occlusion produced by photodynamic thrombosis using a new photosensitizer. Curr Eye Res 2002;25:317–323.
9.
Joussen AM, Kruse FE, Rohrschneider K, Völcker HE: Devitalisierung von Linsenepithelzellen durch Farbstoff-verstärkte Therapie. Ophthalmologe 1995;92:581–590.
10.
Andley U: Photooxidative stress; in Albert DM, Jakobiec FA (eds): Principles and Practice of Ophthalmology. Philadelphia, WB Saunders, 1992, vol 1, pp 575–590.
11.
Charulatha V, Rajaram A: Influence of different crosslinking treatments on the physical properties of collagen membranes. Biomaterials 2003;24:759–767.
12.
Bailey AJ, Sims TJ, Avery NC, Miles CA: Chemistry of collagen cross-links: Glucose-mediated covalent cross-linking of type-IV collagen in lens capsules. Biochem J 1993;296:489–496.
13.
Krag S, Olsen T, Andreassen TT: Biomechanical characteristics of the human anterior lens capsule in relation to age. Invest Ophthalmol Vis Sci 1997;38:357–363.
14.
Goosey JD, Zigler JS, Kinoshita JH: Cross-linking of lens crystallins in a photodynamic system: A process mediated by singlet oxygen. Science 1980;208:1278–1280.
15.
Russell SR, Shepherd JD, Hageman GS: Distribution of glycoconjugates in the human retinal internal limiting membrane. Invest Ophthalmol Vis Sci 1991;32:1986–1995.
16.
Mohan PS, Spiro RG: Macromolecular organization of basement membranes. J Biol Chem 1986;261:4328–4336.
17.
Horiguchi M, Miyake K, Ohta I, Ito Y: Staining of the lens capsule for circular continuous capsulorhexis in eyes with white cataract. Arch Ophthalmol 1998;116:535–537.
18.
Auffarth GU, Wesendahl TA, Newland TJ, Apple DJ: Capsulorhexis in the rabbit eye as a model for pediatric capsulectomy. J Cataract Refract Surg 1994;20:188–191.
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2004
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