Indocyanine green in vitreomacular surgery—(why) is it a problem?

Abstract

T HE REMOVAL OF THE INTERNAL LIMITING MEMbrane (ILM) has been shown to be an effective treatment option in several vitreomacular diseases such as macular holes,1 macular pucker, or macular edema. As the ILM being part of the vitreoretinal interface represents a scaffold for proliferating cells, ILM peeling is currently considered a prophylactic measure against persistent or recurrent macular puckers or macular holes.1 Furthermore, ILM peeling seems to improve postoperative anatomical and functional outcome in macular holes.2 There are only single reports suggesting that ILM peeling correlates with functional deterioration.3 A large prospective study revealed small, paracentral, yet asymptomatic scotomata detected by microperimetry after ILM peeling for macular hole repair.1 This observation may indicate a discrete mechanical trauma to the nerve fiber layer associated with ILM peeling.4 However, the ILM is a very delicate and nearly invisible structure, and its removal represents a challenge for the vitreoretinal surgeon. It is not only difficult to grasp the ILM, but also to determine where the ILM has already been stripped off and where additional peeling might be necessary. Therefore, effort was made to develop a technique to visualize the ILM. One recent approach was the introduction of indocyanine green (ICG) for intraocular application during vitreomacular surgery. A tricarbocyanine dye, indocyanine green (ICG) was initially introduced in 1957. It soon became popular to record dilution curves to measure cardiac output or organ perfusion and was also used for liver function diagnosis. The principal advantages were the confinement to the vascular compartment by binding to plasma proteins and rapid excretion almost exclusively into the bile. Typically, ICG has a maximum peak of absorption at approximately 800 nm. However, it has been shown that the absorption qualities of ICG show significant variations depending on the solvent medium, for example, plasma or water, and the dye concentration. Another influence on the absorption spectrum results from progressive aggregate formation with increasing concentration. In ophthalmology, the main indication is the intravenous application for the imaging of the choroidal circulation by ICG angiography. The intravenous application of the dye has a long history of safety. Additionally, ICG can be used as a vital dye for donor corneal endothelium and to assist capsulorhexis in eyes with mature cataract. In addition, it was observed that ICG may also stain to some degree the vitreous cortex (especially the anterior vitreous base) and the ILM more intensely around the edges of a retinal hole, but no staining around vessels was seen. Recently, ICG was also suggested for photodynamic therapy at the choriocapillaris layer. The first description of ICG staining of the ILM was by Vivian Kim at the American Academy of Ophthalmology in 1999 (poster #349). One of the first reports on ICGassisted ILM peeling was published by Kadonosono and associates in the year 2000.5 It was, furthermore, demonstrated that ICG selectively stains the ILM, as a staining effect could only be achieved when the vitreous cortex or epiretinal tissue was thoroughly removed.6 Additionally, a “negative” staining effect might be useful under special circumstances such as persistent/recurrent holes, where areas of peeled and areas of not removed ILM could be identified during a second surgical approach. Clinical and histopathologic evaluations indicated that the ILM is often unintentionally removed at least in part with the epiretinal cellular layer in macular pucker surgery. However, a complete removal of the ILM reduces reproliferation of epiretinal cells and leads to better functional results.2 Therefore, ICG could be used to assist the removal of tissue (ILM) subsequent to the initial peeling of the visible epiretinal fibrocellular layer. Several published studies have emphasized the obvious advantages of the dye in visualization and easier and more complete removal of the ILM. Consequently, dye-assisted vitrectomy has been received with great enthusiasm. Accepted for publication April 15, 2003. InternetAdvance publication at ajo.com April 22, 2003 From the Ludwig-Maximilians Universitat Munchen, Munchen, Germany (A.K.); and Vanderbilt University Medical Center, Nashville, Tennessee (P.S.). Inquiries to Anselm Kampik, MD, Department of Ophthalmology, Ludwig-Maximilians Universitat Munchen, Mathidenstrasse 8, Munchen, Germany D80336; fax: ( 49) 89-5160-4778.