Morphological damage in rabbit retina caused by subretinal injection of indocyanine green

Intravitreal indocyanine green is toxic to the retinal cells

BACKGROUND

Indocyanine green (ICG) is widely used to stain the epiretinal membranes and internal limiting membranes during the pars plana vitrectomy (PPV). This study aims to evaluate the effect of ICG on rat retinas and various retinal cell lines, including ARPE-19 cells, rMC-1 cells, BV2 cells, HRMECs and R28 cells.

METHODS

ICG solutions were prepared and diluted with glucose solution (GS) according to the standard clinical protocols. The retinal cell lines, including ARPE-19 cells, rMC-1 cells, BV2 cells, HRMECs and R28 cells, were treated with the following solutions: normal glucose (NG, 5 mM), GS-1 (92.5 mM glucose), GS-2 (185.02 mM glucose), ICG-1 (92.5 mM glucose + 0.43 mM ICG), or ICG-2 (185.02 mM glucose + 0.86 mM ICG) for durations of 15 or 30 min. In vivo, the right eyes of the rats were intravitreally injected with ICG-1 or ICG-2 (2 μL), while the left eyes were intravitreally injected with GS-1 or GS-2, served as the osmotic controls, for 30 min or 60 min. The rats intravitreally injected with an equivalent volume of NG or 1x phosphate-buffered saline (1x PBS) were served as the normal control or vehicle control. The cell viability was measured with the Cell Counting Kit-8 (CCK-8), while the cell death in retinal cryosections was detected with the TUNEL assay.

RESULTS

The viabilities of the different retinal cell lines involved in this study were significantly reduced by both ICG-1 and ICG-2 treatments at both time points, with ICG-2 resulting in lower cell viability compared to the NG group and the osmotic control group. Additionally, GS-2 treatment also exhibited a decrease in retinal cell viabilities in vitro. To further confirm these results, intravitreal injection of ICG or GS induced more apoptotic cell death in rat retinas as evidenced by the TUNEL assay.

CONCLUSIONS

The exposure of ICG or its solvent leads to an augmented retinal cell death, which is directly proportional to the concentration and duration of exposure, both in vivo and in vitro. Caution should be exercised during vitrectomy procedures involving ICG administration during clinical practice. It is recommended to advocate for lower concentrations of ICG with reduced exposure time during ocular surgeries.

Visual Acuity after Vitrectomy and Epiretinal Membrane Peeling with or without Premacular Indocyanine Green Injection

PURPOSE

To compare postoperative visual acuity of eyes operated for an epiretinal membrane (ERM), with or without intraoperative intraocular indocyanine green (ICG) injection.

METHODS

Retrospective study of 75 pseudophakic eyes with epiretinal membrane operated by vitrectomy-peeling. In 20 cases operated in 2001 and 2002 (Group 1), ICG diluted in 5% glucose solution was injected intraoperatively into the vitreous. In another group of 55 cases operated between 1996 and 1999 (Group 2), ICG was not used.

RESULTS

The mean visual acuity was 0.32(+1) and 0.32(+2) preoperatively, 0.4(+2) and 0.5 at 1 month, and 0.63 and 0.63(+2) on the final examination in Groups 1 and 2, respectively. Visual acuities were not significantly different between the two groups.

CONCLUSIONS

Premacular injection of ICG during vitrectomy to facilitate epiretinal membrane peeling did not appear to compromise postoperative improvement of visual acuity. However, its use is questioned since it did not yield better postoperative results and because potential toxic adverse reactions could not be excluded by this study.

Complications of Macular Peeling

Macular peeling refers to the surgical technique for the removal of preretinal tissue or the internal limiting membrane (ILM) in the macula for several retinal disorders, ranging from epiretinal membranes (primary or secondary to diabetic retinopathy, retinal detachment…) to full-thickness macular holes, macular edema, foveal retinoschisis, and others. The technique has evolved in the last two decades, and the different instrumentations and adjuncts have progressively advanced turning into a safer, easier, and more useful tool for the vitreoretinal surgeon. Here, we describe the main milestones of macular peeling, drawing attention to its associated complications.

Retinal Damage Induced by Internal Limiting Membrane Removal

The internal limiting membrane (ILM), the basement membrane of the Müller cells, serves as the interface between the vitreous body and the retinal nerve fiber layer. It has a fundamental role in the development, structure, and function of the retina, although it also is a pathologic component in the various vitreoretinal disorders, most notably in macular holes. It was not until understanding of the evolution of idiopathic macular holes and the advent of idiopathic macular hole surgery that the idea of adjuvant ILM peeling in the treatment of tractional maculopathies was explored. Today intentional ILM peeling is a commonly applied surgical technique among vitreoretinal surgeons as it has been found to increase the rate of successful macular hole closure and improve surgical outcomes in other vitreoretinal diseases. Though ILM peeling has refined surgery for tractional maculopathies, like all surgical procedures it is not immune to perioperative risk. The essential role of the ILM to the integrity of the retina and risk of trauma to retinal tissue spurs suspicion with regard to its routine removal. Several authors have investigated the retinal damage induced by ILM peeling and these complications have been manifested across many different diagnostic studies.

Toxicity profiles of subretinal indocyanine green, Brilliant Blue G, and triamcinolone acetonide: a comparative study

BACKGROUND

This study introduces a novel porcine model to examine the histopathological and electrophysiological consequences of retinotoxicity exerted by dyes commonly used for internal limiting membrane (ILM) staining.

METHODS

Indocyanine green (ICG) 0.5 mg/ml, Brilliant Blue G (BBG) 0.25 mg/ml and triamcinolone acetonide (TA) 13 mg/ml was injected subretinally in 12 vitrectomized pig eyes. At 6 weeks, retinas were examined by multifocal electroretinography (mfERG), ophthalmoscopy, fluorescein angiograpy, histopathology, and apoptosis assay.

RESULTS

mfERG responses were significantly lower in ICG-injected eyes than in healthy fellow eyes (p = 0.039). The ratio between injected eyes and healthy fellow eyes was lower in the ICG group than in the BBG (p = 0.009) and TA group (p = 0.025). No difference between BBG and TA existed. All retinas were reattached, and fluorescein angiographies showed a window defect corresponding to the injected areas but no blood-retina barrier break-down. Histopathology confirmed damage to the outer retina after ICG, but not after BBG and TA. No apoptosis was found at 6 weeks.

CONCLUSIONS

Subretinal ICG induces histological and functional damage to the retina, suggesting that ICG should be used with caution in macular hole surgery, where subretinal migration can occur. In contrast, BBG and TA appear safe after subretinal injection.

Formation of near-infrared fluorescent nanoparticles for medical imaging

Aims: Indocyanine green (ICG) is a US FDA-approved near-infrared fluorescent, water-soluble dye used for diagnostics in vitro and in vivo. The aim of this study was to develop insoluble nanoparticles based on a cationic polymer, ICG and a targeting molecule. The particles are intended for oral administration in the colon, having fluorescence in near-infrared, thus enabling remote detection. Materials & methods: An aqueous dispersion of particles formed from Eudragit-RS by simple precipitation method possessing a mean size of approximately 100 nm and zeta potential of +16 mV was produced. Results: These particles are capable of binding both ICG and fluorescein isothiocyanate–IgG via noncovalent interactions. These composite particles retain the emission characteristics of the fluorescent precursors and also exhibit potential specific recognition ability. The particles were stable in intestinal fluid and are composed only of materials that are FDA approved. Conclusion: The nanoparticles may be suitable for in vivo imaging and therapy by oral delivery systems.

Vital staining with indocyanine green: a review of the clinical and experimental studies relating to safety

Indocyanine green (ICG) is extremely effective when used as a vital stain during macular hole surgery. By staining the internal limiting membrane, ICG facilitates removal of this delicate and sometimes hard to visualize structure. There is, however, considerable debate regarding its safety. This review considers the clinical and experimental studies of ICG and a related agent, infracyanine green. Some clinical papers show visual field defects, reduced visual acuity, and persistence of ICG at the macula and optic nerve. Other clinical studies fail to demonstrate toxicity. The experimental studies are also conflicting, but there are emerging trends. These suggest that surgeons who continue to use ICG should use concentrations not greater than 0.05 mg/ml, in fluid-filled eyes, with short exposure times, iso-osmolar solutions, and avoid proximal or prolonged endoillumination of stained tissue. A smaller number of studies suggest that infracyanine green produces similar staining to ICG, and may possibly be safer, but there are too few well-designed studies to reach a conclusion. Although the use of ICG continues, on the balance of evidence, this review suggests that it is has the potential to produce subtle visual damage.

Mechanisms of intravitreal toxicity of indocyanine green dye: implications for chromovitrectomy

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Biocompatibility of brilliant blue G in a rat model of subretinal injection

PURPOSE

To evaluate the toxicity of brilliant blue G (BBG) compared with those of indocyanine green (ICG) and trypan blue (TB) in a rat model of subretinal injection.

METHODS

Retinal detachment was produced by subretinal injection of the dyes. The biocompatibility of BBG (0.25 mg/mL) was evaluated over 2 months and 2 weeks by ophthalmic examinations. The eyes were enucleated and analyzed by light, fluorescence, as well as transmission electron microscopy. Apoptotic cell death was detected by TdT-dUTP terminal nick-end labeling. The results were compared with those for ICG (5 mg/mL) and TB (1 mg/mL).

RESULTS

ICG caused retinal degeneration and retinal pigment epithelial (RPE) cell atrophy 2 weeks after subretinal injection. Apoptotic cell death was detected in the inner and outer nuclear layers and the RPE layer, especially the photoreceptors. TB caused less retinal degeneration, mainly in the area detached by the subretinal injection. BBG had no detectable toxic effects after 2 months and 2 weeks. Apoptotic cell death was detected in the ICG and TB groups, mainly in the photoreceptors.

CONCLUSIONS

Subretinal injection of the dyes caused retinal cell degeneration at lower concentrations than those reported for intravitreous injection. However, subretinal injection of BBG at 0.25 mg/mL appeared to provide satisfactory biocompatibility.

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

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Preclinical investigation of internal limiting membrane staining and peeling using intravitreal brilliant blue G

PURPOSE

To investigate the effects of intravitreal brilliant blue G (BBG) on the morphology and functions of the retina and its possible use for staining and peeling of the internal limiting membrane (ILM).

METHODS

Rat eyes (n = 78) underwent gas compression vitrectomy. BBG solution was then injected into the vitreous cavity. The eyes were enucleated at 2 weeks and 2 months. Light as well as electron microscopy, terminal nick-end labeling staining, and electroretinography (ERG) were used to investigate retinal damage and function. To test the clinical potential of BBG, ILM staining was evaluated in primate eyes after pars plana vitrectomy followed by ILM peeling.

RESULTS

In the rat eyes, no pathologic changes were observed with light microscopy. Electron microscopy revealed that high doses of BBG induced vacuolization in the inner retinal cells, but apoptosis was not detected. There was no reduction in the amplitude of the ERG waves. In the primate eyes, the ILM was clearly visualized after the intravitreous injection of BBG and was peeled off easily from the retina.

CONCLUSIONS

These results demonstrate that BBG, which has low potential for toxicity, high staining ability, and ease of handling, is a good candidate dye for ILM peeling.

Assessment of macular function by multifocal electroretinography following epiretinal membrane surgery with indocyanine green-assisted internal limiting membrane peeling

PURPOSE

To evaluate the changes in macular function and potential retinal toxicity in epiretinal membrane (ERM) surgery with indocyanine green (ICG)-assisted internal limiting membrane (ILM) peeling using multifocal electroretinography (mfERG).

METHODS

Thirteen eyes of 13 patients were randomly assigned to have ERM surgery with ILM peeling using 0.5 mg/ml or 1.25 mg/ml ICG staining. Patients were examined at baseline and at 3 and 6 months postoperatively. The postoperative mfERG N1 and P1 response amplitudes and peak latencies of various ring eccentricities were assessed and compared with baseline to determine any serial changes.

RESULTS

After surgery, the median best-corrected visual acuity improved from 20/70 at baseline to 20/30 at 6 months postoperatively (Wilcoxon signed-ranks test, P=0.004). At 3 months postoperatively, the 0.5 mg/ml group showed no significant changes in N1 and P1 response amplitudes and peak latencies, whereas the 1.25 mg/ml ICG group showed significant reductions in N1 and P1 response amplitudes compared with baseline. No significant changes in mfERG responses were observed in either group at 6 months after surgery.

CONCLUSIONS

Our mfERG findings suggested that the use of a higher concentration of ICG for ILM staining might result in transient retinal functional impairment postoperatively. The lowest possible concentration of ICG should be used intraoperatively to minimize potential retinal toxicity.

Retinal ganglion cells toxicity caused by photosensitising effects of intravitreal indocyanine green with illumination in rat eyes

AIM

To investigate the effects of indocyanine green (ICG) with or without illumination on rat retinal ganglion cells (RGC) and retinal morphology.

METHODS

Intravitreal injections of 1.0 mg/ml ICG solution were performed in rat eyes with or without subsequent illumination for 5 minutes. Eyes in the control group had intravitreal injections of balanced salt solution with illumination. Retrograde labelling of RGC with 6% Fluoro-Gold was performed 1 month later and RGC densities were compared between the three groups. Light microscopy with measurements of outer nuclear layer (ONL) and inner nuclear layer (INL) thicknesses were also performed and compared.

RESULTS

Eyes with ICG without illumination showed insignificant reduction in RGC density compared with the control group (p = 0.28), whereas a significant decrease in RGC density was found in eyes that had ICG injection with illumination (p = 0.036). A significant increase in ONL thickness was also observed in the ICG with illumination treated eyes compared with the ICG without illumination and the control groups (p<0.001). No significant difference in INL thickness was observed between the three groups.

CONCLUSIONS

Intravitreal injection of 0.1 mg/ml ICG in rat eyes followed by illumination resulted in photosensitising toxicity to RGC. Lower ICG concentration or illumination level should be considered when performing ICG assisted macular surgery.

The effects of indocyanine green and endoillumination on rabbit retina: an electroretinographic and histological study

AIM

To evaluate the functional and morphological retinal toxicity associated with intravitreal injection of indocyanine green (ICG) dye in rabbit eyes during vitrectomy with endoillumination.

METHODS

20 eyes of 10 New Zealand pigmented rabbits were used in the study. All eyes underwent pars plana vitrectomy and removal of posterior vitreous cortex under endoillumination. In one eye of each rabbit, intravitreal injection of 0.1 ml of 2.5 mg/ml ICG was applied for 30 seconds followed by 10 minutes of endoillumination. The control eye had endoillumination only without ICG injection. Dark adapted and light adapted electroretinograms (ERGs) were performed before the surgery and 1 week after surgery for serial comparisons. Rabbits were killed 1 week after surgery and eyes were enucleated for histological examination.

RESULTS

Serial ERG comparisons showed significant reduction in the light adapted a-wave amplitude (p = 0.037) and significant delays in the dark adapted and light adapted b-wave latencies (p = 0.020 and p = 0.038, respectively) in the ICG treated eyes. Histological examinations demonstrated loss of photoreceptor outer segments with focal absence of photoreceptors in some areas in the ICG injected eyes.

CONCLUSIONS

Vitrectomy followed by intravitreal injection of 2.5 mg/ml ICG for 30 seconds with endoillumination may result in retinal toxicity causing functional and morphological retinal damages in rabbit eyes. The lowest concentration of ICG should be used if necessary for intraocular use to prevent potential retinal toxicity.

Intravitreal Staining of the Internal Limiting Membrane Using Indocyanine Green in the Treatment of Macular Holes

Surgical management of macular holes consists of pars plana vitrectomy, removal of the posterior hyaloid facia, and peeling of the epiretinal membranes (ERM). Additionally, removal of the internal limiting membrane (ILM) may enable an increase in the anatomic and functional success rates. However, recognition of fine ILM is difficult thus increasing the time that the macula is exposed to intraoperative light. Staining the ILM with indocyanine green (ICG) dye during vitrectomy facilitates recognition of the ILM and assures that all adjacent ERM are removed. Therefore, ICG-assisted ILM peeling has gained worldwide popularity among vitreoretinal surgeons. However, there are some concerns about the intravitreal ICG application. Reports in the literature described a variety of application techniques using different concentrations. The postoperative outcomes were controversial reporting heterogeneous anatomical and functional outcomes after ICG application, as well as descriptions of adverse effects related to the dye. We discuss the indications, techniques, surgical results, and complications after intravitreal ICG injection for the treatment of macular holes.

Long-term follow-up of indocyanine green–assisted peeling of the retinal internal limiting membrane during vitrectomy surgery for idiopathic macular hole repair

OBJECTIVE

To determine the long-term efficacy of indocyanine green (ICG)-assisted retinal internal limiting membrane (ILM) peeling during macular hole repair.

DESIGN

Retrospective, interventional, noncomparative case series.

PARTICIPANTS

One hundred twenty-one eyes of 114 patients with stage 2, 3, or 4 idiopathic macular holes that underwent ICG-assisted macular hole repair during the period of August 1999 to January 2003.

INTERVENTION

All eyes underwent a pars plana vitrectomy, including peeling of the posterior cortical hyaloid when necessary. Indocyanine green dye (0.5%) was instilled over the macula, and after removal of the ICG, the retinal ILM was peeled. Medium- to long-acting gas tamponade was used in all cases, and all patients were asked to position themselves facedown for 1 to 2 weeks.

MAIN OUTCOME MEASURES

Long-term postoperative anatomic results, visual acuity (VA), and complications.

RESULTS

Patients were observed postoperatively for an average of 26 months (range, 12-53). Anatomic closure of the macular hole was achieved in 118 eyes (98%) with a single surgery. Reoperation was successful at closing 2 of the 3 macular holes that did not close initially. One macular hole reopened 16 months after the original surgery, and the patient has not yet undergone further surgery. Visual acuity improved by > or =2 lines in 116 eyes (96%). Mean visual improvement after surgery was 6 lines (range, 0-14), and 96 eyes (79%) achieved a final VA of 20/50 or better. There were no intraoperative or postoperative complications attributed to the use of ICG.

CONCLUSIONS

Long-term follow-up of patients who underwent ICG-assisted ILM peeling for idiopathic macular hole repair demonstrates excellent anatomic and visual results.

Indocyanine green-assisted ILM peeling in macular hole surgery revisited

PURPOSE

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.

DESIGN

Prospective, nonrandomized interventional case series.

METHODS

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.

RESULTS

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.

CONCLUSIONS

A brief intravitreal application of low dose ICG may provide a safe ILM peeling in vitreomacular surgeries.