Application Of Indocyanine Green Research Articles

Meta-Analysis of Chromovitrectomy with Indocyanine Green in Macular Hole Surgery

Purpose: To report a meta-analysis of the literature comparing internal limiting membrane (ILM) peeling with and without indocyanine green (ICG) staining in macular hole (MH) treatment. Methods: A Pubmed search was conducted from January 1999 to June 2004. Manuscripts describing the anatomical and functional outcomes of vitrectomy plus ILM peeling with and without ICG application in MH surgery were reviewed. A statistical meta-analysis was performed including studies which defined anatomical outcomes as closure of the MH and disappearance of the fluid cuff and functional outcomes as improvement of 2 or more Snellen lines. A secondary outcome was to investigate the incidence of retinal pigment epithelium (RPE) alterations with and without ICG staining in MH surgery. Results: Results including all types of MHs in 837 eyes indicated the same anatomical success but worse functional outcomes in the group with ICG application (p = 0.0008; odds ratio = 0.587, 95% confidence interval = 0.427–0.808). A higher incidence of RPE alterations in the ICG injection group was observed. The incidence of RPE alterations was found to be 1.98%, whereas RPE changes were noted in 13.83% of 201 patients with ICG application (odds ratio = 7.998). Conclusion: This meta-analysis of previous reports comparing ILM peeling with and without intravitreal ICG application in the treatment of MHs demonstrated statistically worse functional outcomes when ICG was applied (p = 0.0008). A higher number of RPE alterations were observed in the ICG-stained group.

MECHANISMS OF INTRAVITREAL TOXICITY OF INDOCYANINE GREEN DYE

Indocyanine green (ICG) dye was shown to improve the visualization of preretinal tissues during chromovitrectomy. However, controversy arose regarding the safety of intravitreal ICG application, because worse functional outcomes and a higher incidence of retinal pigment epithelium (RPE) changes and visual field defects were reported. The mechanisms of ICG-related toxicity and their relevance for chromovitrectomy are reviewed. A literature search was performed from 1998 through 2005 for relevant information related to the mechanisms of intravitreal ICG toxicity. Animal and clinical data on intravitreal ICG-related toxicity were collected to clarify the mechanisms of the risk of intravitreal ICG injection. Over 80 controversial in vitro, ex vivo, and in vivo animal investigations as well as clinical reports on intravitreal ICG staining were found in the literature. The main postulated mechanisms of intravitreal ICG-related toxicity were as follows: biochemical direct injury to the ganglion cells/neuroretinal cells, RPE cells, and superficial retinal vessels; apoptosis and gene expression alterations to either RPE cells or neuroretinal cells; osmolarity effect of ICG solution on the vitreoretinal interface; light-induced injury; and mechanical cleavage effect to the internal limiting membrane/inner retina. Whereas the exact mechanism of intravitreal ICG-related damage remains yet to be determined, most animal experiments proposed that ICG dye has a dose-dependent toxic effect on retinal tissue. This hypothesis was supported by clinical data, because better functional outcomes were obtained when low dye concentrations and short incubation times were reported. Much evidence supports that ICG dye has a dose-dependent toxic effect on the retina. Therefore, the following recommendations to minimize toxic effects on the retina are proposed: dye injection in concentrations as low as possible; avoidance of repeated ICG injections onto bare retina; dye injection far from the macular hole to prevent direct dye contact with the RPE; short incubation time of ICG in the vitreous cavity to diminish the concentration in contact with the retinal tissue; and the light pipe kept far from the retina throughout the whole surgical procedure.

ANATOMICAL AND VISUAL OUTCOMES OF IDIOPATHIC MACULAR HOLE SURGERY WITH INTERNAL LIMITING MEMBRANE REMOVAL USING LOW-CONCENTRATION INDOCYANINE GREEN

To report the anatomical, visual, and optical coherence tomography (OCT) results of using a brief application of a low concentration of indocyanine green (ICG) to assist the removal of internal limiting membrane (ILM) during idiopathic macular hole repair. Retrospective, interventional, noncomparative case series of 59 eyes of 57 patients with stage 2, 3, or 4 idiopathic macular holes who underwent pars plana vitrectomy with removal of ILM assisted by a brief (<30 seconds) intravitreal application of 0.125% (1.25 mg/mL) ICG. The median follow-up period was 13 months (range, 2-40 months). Anatomical closure of the macular hole was achieved in 58 eyes (98%) with a single surgery. Visual acuity improved from a preoperative mean of 20/100 to 20/60 postoperatively (P < 0.0001). Twenty-nine eyes (49%) had postoperative visual acuity of 20/50 or better. Visual acuity improved by > or =2 lines in 43 eyes (73%) and between 0 and 2 lines in 13 eyes (22%) and decreased in 3 eyes (5%). Postoperative OCT showed closure of macular hole with normal foveal depression in 49 (89%) of 55 eyes. A brief application of ICG at a low concentration appears to provide a safe and effective way of assisting ILM peeling during idiopathic macular hole surgery.

Indocyanine Green Staining Facilitates Detection of Bleb Leakage During Trabeculectomy

To report a new technique to visualize bleb leakage using indocyanine green (ICG) staining during trabeculectomy. The ICG solution was widely applied over the filtering bleb including the conjunctival wound before completion of trabeculectomy. This procedure was performed in 48 eyes of 44 consecutive patients undergoing trabeculectomy between December 2004 and October 2005. Without staining, bleb leakage was not identified by the direct observation under the operating microscope. ICG staining clearly visualized aqueous leakage from the bleb in 5 eyes (10.4%). The bleb leakage in these eyes was easily repaired with 10-0 nylon sutures, and no eyes, including these 5 cases, showed bleb leakage after surgery. There were no intraoperative and postoperative complications related to ICG application. The application of ICG during trabeculectomy is a simple and useful technique to facilitate detection and repair of the bleb leakage.

Healing of rabbits’ cornea following laser welding: effect of solid and semisolid formulations containing indocyanine green

Laser-assisted tissue welding using chromophores and/or biomaterials as solders may offer several advantages over conventional methods (sutures and staples) such as reduced inflammation and foreign body response, faster healing, and simplicity. This technique makes it possible to perform sutureless surgery and repair wounds that are difficult or impossible to repair using standard surgical techniques. This in turn may be particularly important in ophthalmology, where conventional sutures may cause inflammation, tissue injury, scarring, and stenosis. The objective of this research was the preparation and technological and biological characterization of new solid (S) and semisolid (SS) formulations containing indocyanine green (ICG), which is a chromophore commonly used in laser welding or tissue soldering. The formulations were aimed at improving the cromophore-assisted laser welding process while ensuring the chemical stability of ICG. Polyvinyl alcohol (PVA), sodium hyaluronate (HYAL), sodium alginate (ALG), 5-methylpyrrolidinone chitosan (MPCh), and tamarind seed polysaccharide (TSP) were chosen as vehicles for the ocular application of ICG. The wetting and hydrophilicity characteristics of the solid formulations (film) were evaluated by contact angle and swelling measurements and correlated with the in vitro release of ICG. The biological efficacy of the formulations was evaluated on a corneal cut in a rabbit model by monitoring the healing process after laser welding and comparing it to the healing process of a conventional suture. The best results were obtained with a solid formulation based on TSP that showed high wettability, good chemical stability, and slow release of ICG. Its use resulted in a rapid and safe healing process.

55 POSTER Cell surface proteomic analysis of human renal tumor endothelium

Although indocyanine green (ICG) has promising applications in photothermal therapy (PPT) because of its low toxicity and high efficiency in inducing heat and singlet oxygen formation in response to near-infrared light with a wavelength of approximately 800 nm, its clinical application has been restricted because of its rapid body clearance and poor water stability. Therefore, cell membrane capsules (CMCs) derived from mammalian cells were used to encapsulate negatively charged ICG by temporarily permeating the plasma membrane and resealing using positively charged doxorubicin hydrochloride (DOX). The resulting [email protected]/ICG exhibited a spherical shape, with a diameter of approximately 800 nm. The DOX and ICG encapsulation was confirmed by the UV–vis spectrum; a very small amount of DOX (0.8 μg) and a very high amount of ICG (∼110 μg) were encapsulated in 200 μg CMCs. Encapsulation in the CMCs leads to sustained release of ICG, especially in the presence of positively charged DOX. The temperature enhancement and generation of ROS by ICG encapsulated in CMCs were confirmed upon laser irradiation in vitro, leading to cell death. [email protected]/ICG also can significantly enhance the retention of ICG in a tumor after intratumoral injection in vivo. As a result, combination treatment with [email protected]/ICG and laser irradiation demonstrated much better anticancer efficacy than that of free DOX/ICG and [email protected] The encapsulation of ICG into CMCs, especially with the assistance of DOX, significantly slows down the body clearance of ICG, with a retained PPT effect against tumors, an important step forward in the practical application of ICG in cancer therapy.In this study, cell membrane capsules (CMCs) derived from mammalian cells were used to encapsulate negatively charged indocyanine green (ICG) by temporarily permeating the plasma membrane and resealing, in the presence of positively charged doxorubicin hydrochloride (DOX). The resulting [email protected]/ICG exhibited a spherical shape, with a diameter of approximately 800 nm. Encapsulation in the CMCs leads to sustained release of ICG and thus slower clearance inside body, especially in the presence of positively charged DOX. The system provides a better photothermal effect against tumors, an important step forward in the practical application of ICG in cancer therapy.

Comparison of In vitro Toxicity of Single vs Double Exposures of Indocyanine Green in Human Retinal Pigment Epithelial Cell Cultures

To compare the in vitro effect of a single brief indocyanine green (ICG) exposure with a double exposure on retinal pigment epithelial (RPE) cells. In vitro laboratory experimental study. Human ARPE-19 cells were exposed to a single dilute ICG exposure (0.5 mg/ml) or to two sequential exposures of identical volume and concentration. Viability was measured with a mitochondrial dehydrogenase assay and compared with nonexposed control cells. Cell viability was not statistically different between the single-exposed, double-exposed, or control cell populations. When used intraoperatively to stain the internal limiting membrane, dilute ICG dye sometimes does not adequately enhance visualization of the internal limiting membrane. Occasionally, it is necessary to repeat the dye exposure to achieve the desired visibility. In this study, RPE cells subjected to two consecutive short exposures of ICG showed no marked difference in cell survival when compared with cells exposed to a single application of ICG and to control cells.

Einfluss von Vitalfarbstoffen auf die Funktion der äußeren Blut-Retina-Schranke in vitro

The use of vital dyes in "chromovitrectomy" allows the easier removal of less recognizable structures like epiretinal membranes (EM) or the inner limiting membrane (ILM). In recent years numerous studies demonstrated the use of indocyanine green (ICG), trypan blue (TB) and patent blue (PB) for this indication. Reports of the possible risk of these dyes, i. e. especially ICG, in respect of reduced visual acuity results, possible visual field defects or alterations of the retinal pigment epithelium (RPE) resulted in limitations in their application. Human RPE cells and choroidal endothelial cells were cultured in monolayers on semipermeable membranes representing an in vitro model of the outer blood-retinal barrier. By measurement of the transepithelial electrical resistance (TER) the stable barrier function was determined. Two different models representing an air-filled and a fluid-filled eye were tested on the one hand by addition of the dye to the culture medium and, on the other, by direct application on the cell monolayer. In these two models ICG (5 mg/ml, 0.5 mg/ml, 0.125 mg/ml), TB (1.5 mg/ml, 0.15 mg/ml) and PB (2.4 mg/ml, 0.24 mg/ml) were applied for three minutes and the influence on the barrier function was determined. RPE cell growth was also tested in these two models after the application of ICG, TB and PB. Finally, monolayers of RPE cells were evaluated by transmission electron microscopy (TEM). After application of TB, PB and the lowest concentration of ICG of 0.125 mg/ml, the TER remained stable in both models. In contrast, ICG in a concentration of 5 mg/ml and 0.5 mg/ml caused a significant TER decrease in the model of the air-filled eye, whereas no influence on the function of the outer blood-retinal barrier was noted in the model of the fluid-filled eye. RPE cell growth rates were not influenced by the addition of the vital dyes, with the exception of ICG in a concentration of 5 mg/ml in the model of the air-filled eye, resulting in a temporary reduction of the cell count. In good correspondence to these results also in TEM intercellular blisters were noted after application of 5 mg/mL ICG for 3 minutes in the model of the air-filled eye. However, damage to the RPE cells themselves was not obvious. No pathological changes in the TEM were noted after application of TB and PB. The use of PB and TB at the posterior eye segment seems to be safe concerning damage to the PRE and its barrier function. In contrast, ICG in higher concentrations and with longer application times may cause a toxic effect on RPE morphology and function.

Histology of the Vitreoretinal Interface after Indocyanine Green Staining of the ILM, with Illumination Using a Halogen and Xenon Light Source

To assess the histology of the retinal surface after staining of the inner limiting membrane (ILM) with indocyanine green (ICG) followed by illumination with halogen or xenon light sources in human donor and porcine eyes. Ten eyes of six human donors and six porcine eyes were used in the study. In human donor eyes, the postmortem time varied between 7 and 38 hours, and porcine eyes were evaluated 9 hours after death. In all eyes, the vitreous was removed, and a few drops of 0.5% ICG were poured over the trephined posterior pole and carefully washed out after a period of 1 minute, with balanced salt solution. Then the stained retina was illuminated for 3 minutes with different light sources: a halogen light source of 145-W power or a xenon light source of 50-W power. Adjacent, unstained retina of each eye served as a control to assess postmortem artifacts. In two human and two porcine eyes ICG was applied without illumination. Retinal specimens were evaluated by light and electron microscopy. In human eyes, severe disorganization of the innermost retina and ILM loss were observed after ICG application with subsequent illumination with the halogen light source. After illumination with the xenon light source, there was only slight vacuolization of the innermost retina, with mostly intact Muller cells. The ILM remained in situ in relation to the retinal surface. Intact cellular architecture was found in all specimens after ICG staining without subsequent illumination and control specimens of unstained retina. In porcine eyes, no impact attributable to the light source or ICG alone was noted in this experimental setting. These findings suggest that adverse effects of ICG at the retinal surface may depend on the light source used during vitrectomy and correlate with the emission spectrum of the different light sources. In addition, care should be taken when comparing results obtained in human eyes and porcine eyes.

Chromovitrectomy: a new field in vitreoretinal surgery

Staining tissues during vitreo-retinal surgery, “chromovitrectomy”, has become a popular approach to visualize preretinal structures. Initially, Burk et al. described in 2000 the intravitreal administration of indocyanine green (ICG) to stain the internal limiting membrane (ILM) [3]. There is general agreement that ICG-assisted ILM peeling is then much facilitated, as the surgeon can easily observe the edge of the ILM rhexis thus ensuring a complete ILM removal. Consequently, trypan blue (TB) arose as the second-generation of vital dyes for chromovitrectomy [24]. Currently, triamcinolone acetonide (TA) has been added as an alternative stain for chromovitrectomy [21]. The rationale for chromovitrectomy is simple, as most preretinal structures have a semitransparent appearance. Over 90 controversial reports have been published on chromovitrectomy in the last 4 years [18]. ICG, TB, and TA are currently used for chromovitrectomy based on their familiarity for other ophthalmic applications. While ICG has been approved for intravenous application in retinal and choroidal angiography, TB has been applied for the staining of the anterior capsule during cataract surgery. Intravitreal TA injection can be applied in the treatment of several types of macular edema. Although TB and ICG demonstrated no adverse effects under those previous ophthalmic applications, their intravitreal use may pose the risk of posterior-segment toxicity. In fact, critical reassessment replaced initial excitement among vitreoretinal surgeons as the group in Munich, Germany, described worse functional outcomes after ICGassisted ILM peeling in macular hole (MH) surgery [10]. ICG staining was postulated to lead to a deeper cleavage plane in ILM dissection since their histologic analysis demonstrated Muller cell membranes adherent on the retinal ILM. Another concern on ICG-use refers to a possible higher incidence of retinal pigment epithelium (RPE) defects [18]. Although Gandorfer et al. showed severe histologic damage to the inner retina after ICG plus light exposure to wavelengths beyond 620 nm in human donor eyes [6], Grisanti et al. obtained opposite results using fresh enucleated pig eyes [9]. Further in-vivo experiments with different animal models such as rats [11], rabbits [14], and pigs [4] revealed a dose-dependent dye toxicity to various retinal cells after ICG application alone or plus light-pipe illumination. Possible toxic effects to the retinal tissue with TB have also been described in animal studies, especially in concentrations above 0.2% [24]. In addition, intravitreal TA injection may cause pseudo or infectious Presented at the Vail Vitrectomy meeting, Colorado, USA, 2004.

Indocyanine green-assisted ILM peeling in macular hole surgery revisited

To report visual outcomes after peeling of the internal limiting membrane (ILM) using a brief application of low dose indocyanine green (ICG) for macular hole repair. Prospective, nonrandomized interventional case series. A consecutive series of 16 eyes of 14 patients with full-thickness macular hole underwent vitrectomy and peeling of the ILM with an intravitreal application of 0.05% ICG for less than 10 seconds. The ILM could be removed uneventfully in 5 of 16 cases after a single ICG application and in 11 cases after a second ICG application. The macular hole was closed in 15 (93.7%) of 16 cases after a single surgery and in one case after a repeat surgery, as evaluated by optical coherence tomography. A significant visual acuity improvement was achieved as the mean logarithm of the minimum angle of resolution was from 0.600 preoperatively (equivalent to approximately 5/20 in the conventional 20 foot numerator form) to 0.213 (12/20) at the end of follow-up (P < .0001). None of the cases developed peripheral visual field defect. Ophthalmoscopies or optic coherence tomographic images did not reveal any disruption at the level of the retinal pigment epithelium. A brief intravitreal application of low dose ICG may provide a safe ILM peeling in vitreomacular surgeries.

Optic nerve atrophy after vitrectomy with indocyanine green-assisted internal limiting membrane peeling in diffuse diabetic macular edema

To report anatomic and visual outcomes of vitrectomy and indocyanine green (ICG)-assisted peeling of the retinal internal limiting membrane (ILM) in the treatment of diffuse diabetic macular edema. In a retrospective interventional case series, 15 eyes of 11 patients with refractory diffuse diabetic macular edema underwent pars plana vitrectomy with removal of the ILM, which was stained by intravitreal injection of ICG (0.1-0.2 ml of 0.5% ICG), performed by a single surgeon. The patients were followed up for 14-28 months (mean 20.5 months). The main outcome measures were assessment of macular edema by optical coherence tomography and determination of visual acuity and visual field. Intravitreal ICG visualized the ILM to facilitate complete removal of the structure. Qualitative assessment of optical coherence tomography images at the end of follow-up revealed that retinal thickness in the macula appeared nearly normal with or without reappearance of foveal pit in 11 of the 15 eyes (73.3%), decreased in 3 eyes (20.0%), and did not change in 1 eye (6.6%). Best-corrected visual acuity at the end of follow-up improved by 2 lines or more in 4 eyes (26.7%), virtually unchanged in 6 eyes (40.0%), and deteriorated by 2 lines or more in 5 eyes (26.7%). The mean logMAR visual acuity was 0.680 (approximately 12/60) preoperatively and 0.812 (approximately 9/60) postoperatively, the difference being not statistically significant (paired t-test, P=0.445). Seven (46.7%) of the 15 eyes developed optic nerve atrophy that occurred gradually within 6 months after surgery and caused irreversible peripheral visual field defect predominantly affecting the nasal field. Intravitreal application of ICG is beneficial in uneventful ILM peeling to help resolution of diffuse diabetic macular edema, but it may potentially damage the optic nerve fibers and lead to unfavorable visual outcomes.

Nonaxoplasmic transfer of indocyanine green into the optic nerve after intravitreal application.

To investigate whether indocyanine green (ICG) migrates into the optic nerve after intravitreal application in the rabbit eye. Gas vitrectomy was performed in one eye of adult Dutch belted rabbits by pars plana injection of 0.4 ml of 100% C3F8 (n = 10). One week later, vitrectomy was performed and 0.2 ml of 0.25% ICG was instilled into the vitreous cavity of these vitrectomized eyes. After 30 seconds of ICG application, the vitreous cavity was rinsed with balanced salt solution plus. Unoperated rabbits served as controls (n = 2). Globes, optic nerves, and the entire brain were removed, and ICG fluorescence of the specimens was examined with a digital fundus camera starting from the first day to the fourth postoperative week. Other rabbit eyes (n = 2) were injected with ICG directly into the vitreous without vitrectomy, and assessed for ICG signal after 1 day of ICG application. In the second part of the experiment, four rabbit eyes were gas vitrectomized and ICG was instilled onto retina after blockage of axonal flow by vinblastine. They were evaluated on the first (n = 2) and seventh postoperative days (n = 2). No fluorescein was detected in the visual pathways and the brains of the control group of rabbits. The optic nerves of the ICG-instilled eyes were stained diffusely with ICG starting from the first day after surgery. ICG injected nonvitrectomized eyes showed similar ICG staining patterns when compared with vitrectomized eyes. ICG staining pattern of the optic nerve did not differ in vinblastine-pretreated eyes. Fluorescence extended along the intraorbital portion of the optic nerve but did not transport more posteriorly in all animals. At the fourth week after vitrectomy, ICG signal was still detectable, but staining was less intense. Intravitreal ICG injection results in nonaxoplasmic extension into the optic nerve in the rabbit.

A pilot study of ICG laser therapy of acne vulgaris: photodynamic and photothermolysis treatment.

The near-infrared (NIR) laser radiation due to its high penetration depth is widely used in phototherapy. In application to skin appendages, a high selectivity of laser treatment is needed to prevent light action on surrounding tissues. Indocyanine green (ICG) dye may provide a high selectivity of treatment due to effective ICG uploading by a target and its narrow band of considerable absorption just at the wavelength of the NIR diode laser. The goal of this study is to demonstrate the efficacy of the NIR diode laser phototherapy in combination with topical application of ICG suggested for soft and thermal treatment of acne vulgaris. Twenty-two volunteers with facile or back-located acne were enrolled. Skin sites of subjects were stained by ICG and irradiated by NIR laser-diode light (803 or 809 nm). One mg/ml solution of ICG was applied for 5 or 15 minutes to the cleaned skin site. Untreated, only stained and only light irradiated skin areas served as controls. For soft acne treatment, the low-intensity (803 nm, 10-50 mW/cm(2), 5-10 minutes) or the medium-intensity (809 nm, 150-190 mW/cm(2), 15 minutes) protocols were used. The single and multiple (up to 8-9) treatments were provided. The individual acne lesions were photothermally treated at 18 W/cm(2) (803 nm, 0.5 seconds) without skin surface cooling or at 200 W/cm(2) (809 nm, 0.5 seconds) with cooling. The observations during 1-2 months showed that soft acne treatment decreased the number of active elements, reduced erythema and inflammation, and considerably improved the skin state without any side effects. At high power densities (up to 200 W/cm(2)), ICG stained acne inflammatory elements were destroyed for light exposures of 0.5 seconds. Based on the concept that hair follicle, especially sebaceous gland, can be intensively and selectively stained by ICG due to dye diffusion through pilosebaceous canal and its fast uptake by living microorganisms, by vital keratinocytes of epithelium of the canal and sebaceous duct, and by rapidly proliferating sebocytes, new technologies of soft and thermal acne lesions treatment that could be used in clinical treatment of acne were proposed.

Functional outcome of macular hole surgery with and without indocyanine green-assisted peeling of the internal limiting membrane.

To describe the impact of indocyanine green (ICG) staining of the internal limiting membrane (ILM) on the functional outcome of anatomically successful macular hole surgery by comparing consecutive patient series with and without ILM staining. Eighteen consecutive patients who had undergone ICG-assisted vitrectomy (0.05%) for idiopathic macular hole were retrospectively analysed (visual acuity, gain in lines, Goldmann perimetry) and compared with two consecutive series of patients who had undergone macular hole surgery without the use of ICG immediately before (n=22) and after (n=17) the introduction of ICG in our institution. The osmolarity of the ICG solution applied was 275 mosmol, pH was 7.5. Although there was no statistically significant difference in duration of preoperative symptoms (P>0.3) and preoperative visual acuity (P>0.5), the functional outcome in patients after ICG-assisted vitrectomy was significantly lower (P<0.001 for visual acuity). The incidence of visual field defects was 50% (9/18) in patients after ICG application. Our findings suggest potential damage to the neurosensory retina in association with the intraoperative administration of the ICG solution. Whether this is caused by toxic effects of the dye itself, mechanical trauma to the retina or other mechanisms remains unknown.

Persistent subretinal indocyanine green induces retinal pigment epithelium atrophy

Purpose To describe a case of a patient with macular hole with subretinal indocyanine green (ICG) during vitrectomy. Design Interventional case report. Methods A 66-year-old woman with macular hole underwent a vitrectomy with ICG. Results After application of ICG into the vitreous, ICG was introduced in the subretinal space. Indocyanine green was found to be present for more than 6 months. Retinal pigment epithelium atrophy appeared at the site of the lesion. Conclusions Although ICG may be a useful tool for distinguishing the internal limiting membrane and other tissues careful application is required to prevent side effects.

Indocyanine green for successful repair of a long-standing macular hole

Purpose To report on the successful closure of a persistent chronic macular hole using indocyanine green (ICG) during the second surgical approach. Design Interventional case report Methods A patient with a long standing macular hole (18 years) underwent pars plana vitrectomy with peeling of the internal limiting membrane (ILM). While no dye was used during the first operation, ICG (0.05%, Pulsion) was applied during the second procedure. The light source was turned off immediately after the ICG application until the dye was washed out after a period of 15 seconds. Tissue harvested during the second surgical approach was prepared for electron microscopy. Results After the failure of the first operation, areas of incomplete ILM peeling could be stained using ICG and a thorough ILM removal was achieved. Postoperatively, the macular hole was closed, as confirmed by optical coherence tomography. Visual acuity increased from 20/200 to 20/50. No visual field defects were seen postoperatively. There were only few cellular elements adherent to the retinal surface of the ILM as seen during electron microscopy. Conclusion In cases where tractional forces due to incomplete ILM removal are considered responsible for the persistence of a macular hole, ICG is useful to identify areas of unpeeled ILM. Under certain safety precautions no adverse effect on functional outcome was seen.

Axon-tracing properties of indocyanine green.

It has been shown recently that the application of indocyanine green (ICG) over the retinal surface is followed by prolonged staining of the optic disc. This study was performed to analyze the diffusion of ICG in the optic tract. Anterograde diffusion of ICG was evaluated after injection into the vitreous of rabbits. Retrograde diffusion was evaluated after microinjection into the lateral geniculate nucleus of rats. Anterograde and retrograde diffusion occurred along the axons at a rate of about 2 mm per hour when ICG was injected. Anterograde staining of the visual pathway persisted for several weeks. After injection into the lateral geniculate nucleus, fluorescent retinal ganglion cells could be visualized for at least 7 days in conscious rats by conventional infrared photography. Microscopic examination findings of retrograde-labeled retinas showed the presence of ICG vesicles inside the axons, cytoplasm, and dendrites of retinal ganglion cells. No evidence of toxic effects was detected by optical microscopy. Indocyanine green is a fast bidirectional axonal tracer. Injection into normal vitreous results in long-term staining of the visual pathway. In vivo counting of ICG-labeled retinal ganglion cells in rats can be performed for several days after injection. Indocyanine green is therefore potentially of interest for use in experimental neurophysiological studies. The present results suggest that in humans, epiretinal application of ICG results in prolonged staining of the visual pathway. Therefore, additional studies of long-term toxic effects of ICG on neural cells are warranted before recommending its use in humans as an intraoperative tool for vitreoretinal surgery.

The effect of indocyanine-green on functional outcome of macular pucker surgery

PurposeTo compare functional results after surgery for macular pucker either with or without indocyanine-green staining of the internal limiting membrane (ILM) and to evaluate the ultrastructure of the tissue removed. DesignRetrospective analysis of two successive, consecutive, interventional case series. MethodsFunctional outcome (visual acuity, Goldmann perimetry) of 48 eyes of 48 consecutive patients with (group 1, n = 20) or without (group 2, n = 28) intraoperative use of indocyanine-green (ICG) was retrospectively analyzed. For statistical analysis, best-corrected visual acuity measured at the last presentation was considered. Only patients with an idiopathic macular pucker were included. Surgery consisted of three-port pars plana vitrectomy, and removal of epiretinal tissue and the ILM in a second step. Commercially available ICG with a concentration of .05% and an osmolarity of 275 mOsm was used to stain the ILM. The surgical technique used for both groups was identical, except the use of ICG. Epiretinal tissue of all eyes was harvested and prepared for ultrastructural analysis using light and electron microscopy. ResultsFollow-up time was 8.5 months in group 1 and 5.4 months in group 2. Whereas patients operated on without ICG experienced a significant improvement of median best-corrected visual acuity from 20/63 (range, 20/400 to 20/32) preoperatively to 20/40 (range, 20/200 to 20/25) postoperatively (P < .001), median best-corrected visual acuity remained 20/63 before (range, 20/200 to 20/63) and after (range, 20/400 to 20/20) (P > .9) ICG-assisted peeling. There was a statistically significant difference (P = .013) in best-corrected postoperative visual acuity of patients with and without the use of ICG. An improvement of vision was noted in 86% of patients without and 55% of patients with ICG-assisted surgery. Thirty-five percent of patients after ICG application presented with a deterioration of visual acuity. Furthermore, we observed large visual field defects in 7 of 20 patients after ILM staining. No visual field defects were noted after conventional peeling. Histologic analysis revealed clear differences between the two groups concerning the amount of cellular elements adjacent to the retinal surface of the ILM: There was more cellular debris visible in specimens after ICG application during surgery. Additionally, in contrast to surgery without ILM staining, epiretinal cells had ruptured and lost their cellular integrity after ICG-assisted vitrectomy. ConclusionsIndocyanine green-assisted surgery for macular pucker might have an adverse effect on functional outcome. Although there were obvious differences in the ultrastructure of tissue removed during surgery, our observations cannot be explained by histologic analysis alone. Other, so far unknown mechanisms of action must be considered.

Effect of indocyanine green and illumination on gene expression in human retinal pigment epithelial cells.

To investigate the biological effects of indocyanine green (ICG) and acute illumination on human retinal pigment epithelial (RPE) cells. Three concentrations (0, 0.25, and 2.5 mg/mL) of ICG were applied to ARPE19 cells for 1 minute. After isotonic rinsing, the cells were irradiated with a light beam with a wavelength spectrum from 400 to 800 nm and an output of 1850 lumens for 15 minutes. The cells were collected at timed intervals for the investigation of cell death and expression of stress-response genes by reverse transcription-polymerase chain reaction, immunofluorescence, and Western blot analysis. After ICG incubation, photoreactive changes were observed in the RPE cells. A reduction in cellular viability and considerable shrinkage of the cells were observed. The expressions of the apoptosis-related genes p53 and bax and the cell cycle arrest protein p21 were upregulated in cells treated with both ICG and light. Of the early-response genes, the expression of c-fos was specifically enhanced by light, with additive effects from the presence of ICG. Such stimulatory effects on these gene expressions were greater at 2.5 mg/mL than at 0.25 mg/mL ICG. ICG in the presence of acute illumination can elicit cell-cycle arrest and even apoptosis in RPE cells. The establishment of a safety level in the application of ICG in the region of 0.25 mg/mL is recommended.