Indocyanine green effect on cultured human retinal pigment epithelial cells: implication for macular hole surgery

Indocyanine green increases light-induced oxidative stress, senescence, and matrix metalloproteinases 1 and 3 in human RPE cells

PURPOSE

Indocyanine green (ICG) is a commonly used vital dye for macular surgery. Recent reports implicate that its use might be associated with less favourable results regarding postoperative visual outcome and damage of retinal cells, and atrophic degeneration of the retinal pigment epithelium (RPE) has been described. This study investigates the effects of ICG on light-induced senescence of RPE cells.

METHODS

Primary human RPE cells were either pre-incubated with ICG in concentrations of 0.005% and 0.05% or not and then exposed to white light. After 10 min of irradiation viability, induction of intracellular reactive oxygen species (ROS) and senescence-associated β-galactosidase activity (SA β-Gal) were determined. Expression and secretion of matrix metalloproteinases (MMPs) 1 and 3 and their mRNA were determined by RT-PCR and ELISA.

RESULTS

Light exposure decreased RPE cell viability by 46%. Treatment with 0.005% and 0.05% ICG alone decreased RPE cell viability by 7% and 21%. In addition, expression of ROS, SA β-Gal, and MMP-1 and 3 was significantly increased. When 0.005% and 0.05% ICG treatments were combined with light exposure, viability decreased by 69% and 82% compared to the untreated control. Effects on the expression of ROS, SA β-Gal, and MMP-1 and 3 were, depending on the ICG dose, significantly increased when cells were pre-incubated with ICG and then illuminated.

CONCLUSION

In this study, pretreatment with ICG significantly increased light-induced oxidative stress and senescence. This might indicate a potential, supplementary mechanism that could explain RPE alterations and reduced functional results after ICG-assisted internal limiting membrane peeling.

Staining of the internal limiting membrane with the use of heavy brilliant blue G

BACKGROUND

Brilliant blue G (BBG) is frequently used in chromovitrectomy to facilitate internal limiting membrane (ILM) peeling. A study was initiated to evaluate if heavy BBG is safe and effective in staining the ILM.

METHODS

We studied 30 eyes, 23 with idiopathic macular holes and 7 of patients with diabetic macular edema. Removal of the ILMs was assisted by heavy BBG staining. In cases with histopathological correlation the ILMs were evaluated with hematoxylin and eosin, Masson's trichrome, periodic acid-Schiff and glial fibrillary acidic protein staining. In addition, immunohistochemistry was also performed using specific antibodies for vimentin, neuron-specific enolase, factor VIII and CD68. Using the Image-Pro Plus software of Media Cybernetics Co. we found an average thickness in ILMs.

RESULTS

Of the ILM specimens sent, 19/30 (63.33%) could not be processed properly because of the limited sample material, recognizing only fragments of dispersed fibrillar material. In macular hole ILMs we found an average thickness of 1.3 ± 0.65 µm, and in diabetic macular edema ILMs an average thickness of 6.2 ± 1.4 µm.

CONCLUSIONS

In heavy BBG-assisted ILM peeling we observed no intraoperative or postoperative complications after a mean follow-up of 12 months. Heavy BBG could be an effective and safe vehicle for staining the ILM.

Unanticipated vision loss after pars plana vitrectomy

Although advances in vitreoretinal surgical techniques and technology have helped to minimize the risks associated with surgical manipulation of the retina, retinal pigment epithelium, and optic nerve, unanticipated or unexplained visual loss still occurs. We review causes of vision loss encountered after pars plana vitrectomy, including retinal toxicities, vascular events, and optic neuropathies, and we suggest strategies to limit or prevent them.

Tempol protects against intravitreous indocyanine green-induced retinal damage in rats

PURPOSE

Indocyanine green (ICG) has been widely used as a vital dye for macular surgery. However, ICG can be toxic to retinal cells. Here we evaluate whether tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a free radical scavenger, can protect against ICG-induced retinal damage in rats.

METHODS

Brown Norway rats received intravitreal injections of ICG 0.5 % or BSS as controls. Tempol (20 mg/kg BW) or PBS as a control was administered intraperitoneally 24 h and 30 min before ICG and once daily for 7 consecutive days. Tempol was detected in the retina using electron paramagnetic resonance (EPR) spectroscopy. One week after ICG injections, the effects of tempol on retinal toxicity were assessed by retinal ganglion cell (RGC) back-labeling and by light microscopy. Electroretinography (ERG) was performed after 1 and 2 weeks.

RESULTS

ICG administration reduced RGC numbers by 17 % (1,943 ± 45 vs. 2,342 ± 31 RGCs/mm(2)). Tempol treatment rescued RGCs in a significant manner (2,258 ± 36, p < 0.01) and diminished morphological changes detected by light microscopy. ICG-injected eyes showed a significant reduction of ERG potentials only in PBS-treated animals (V(max) 530 ± 145 µV vs. 779 ± 179 µV, p = 0.0052), but not in the tempol-treated group.

CONCLUSIONS

Tempol significantly attenuates ICG-induced toxicity in rat retinas and may therefore be considered for further evaluation as accompanying treatment in ICG-assisted chromovitrectomy.

Low-Concentration Infracyanine Green–Assisted Internal Limiting Membrane Peeling in Idiopathic Macular Pucker 25-Gauge Surgery

Purpose

To investigate the efficacy of 25-gauge infracyanine green–assisted idiopathic macular pucker surgery and to identify prognostic factors.

Methods

In this retrospective interventional case series, 83 patients with idiopathic macular pucker who underwent 25-gauge surgery with infracyanine green–assisted internal limiting membrane (ILM) peeling were retrospectively reviewed. Best-corrected visual acuity (BCVA) measurement, complete ophthalmologic evaluation, and optical coherence tomography were performed at baseline and during follow-up. Preoperative and postoperative prognostic factors were correlated with final visual outcomes.

Results

Mean follow-up was 10.5 months (range 3-44). Best-corrected visual acuity improved from 0.56±0.27 logMAR (±SD) to 0.26 ±0.18 logMAR (p<0.001); central retinal thickness decreased from 441±115 μm to 355±72 μm (p<0.001). Greater postoperative visual gain was correlated with baseline BCVA (r=–0.65, p<0.0001), and BCVA gain after 1 week (r=0.64, p<0.0001) and 1 month (r=0.58, p<0.0001). Final BCVA was influenced by baseline BCVA (r=0.46, p<0.0001), BCVA change after 1 month (r=0.34, p=0.002), and presence of intraretinal fluid (r=0.28, p=0.01). No cases of endophthalmitis, retinal tears, or retinal detachments were reported.

Conclusions

Low-concentration infracyanine green–assisted ILM peeling during minimally invasive surgery is associated with significant visual acuity improvement. Preoperative BCVA and optical coherence tomography appearance may be helpful in predicting the final visual outcome.

Brilliant blue G-assisted peeling of the internal limiting membrane in macular hole surgery

Dye-assisted internal limiting membrane (ILM) peeling and gas tamponade is the surgery of choice for idiopathic macular holes. Indocyanine green and trypan blue have been extensively used to stain the ILM. However, the retinal toxicity of indocyanine green and non-uniform staining with trypan blue has necessitated development of newer vital dyes. Brilliant blue G has recently been introduced as one such dye with adequate ILM staining and no reported retinal toxicity. We performed a 23-gauge pars plana vitrectomy with brilliant blue G-assisted ILM peeling in six patients with idiopathic macular holes, to assess the staining characteristics and short-term adverse effects of this dye. Adequate staining assisted in the complete removal of ILM and closure of macular holes in all cases. There was no evidence of intraoperative or postoperative dye-related toxicity. Brilliant blue G appears to be safe dye for ILM staining in macular hole surgery.

Non-Foveal Macular Holes After PPV for Macular Pucker

Purpose:

To describe six patients (six eyes) who developed an eccentric macular hole after surgery for idiopathic epimacular proliferation.

Materials and Methods:

Review of records from six patients who developed eccentric macular holes postoperatively following vitrectomy in 107 consecutive cases with peeling of the epimacular proliferation and internal limiting membrane (ILM) from June 2004 to January 2009

Results:

Eccentric macular holes were developed from nine days to eight months (mean, 3.1 months) after epimacular proliferation peeling. The ILM was peeled in addition to the epimacular proliferation in five of the six cases. Of the six eccentric macular holes, four were located temporal to the fovea, one was located superior to the fovea, and one was located nasal to the fovea. Final visual acuities after a mean follow-up period of 17.3 months were 20/20 in two eyes, 20/25 in one eye, 20/40 in two eyes, and 5/200 in one eye. The eye with the eccentric macular hole nasal to the fovea had the poorest final visual acuity of 5/200.

Conclusion:

Eccentric macular holes occurring after vitrectomy to remove epimacular proliferation is an uncommon postoperative finding. Various explanations have been suggested for the etiology of these holes, but there is no consensus. We suggested that the ILM tear should be initiated with a diamond dusted knife to reduce the likelihood of injury to the underlying Muller cells that may contribute to the formation of eccentric macular holes.

Outcomes of idiopathic macular epiretinal membrane removal with and without internal limiting membrane peeling: a comparative study

PURPOSE

To compare visual acuity and macular morphology after epiretinal membrane (ERM) removal with and without internal limiting membrane (ILM) peeling.

METHODS

We studied a retrospective interventional case series of 40 eyes in 40 patients with ERM. All patients underwent standard three-port pars plana vitrectomy. In 19 eyes, the ERM alone was removed. In 21 eyes, the ERM was removed and ILM peeling was performed.

RESULTS

Mean best-corrected visual acuity improved significantly in both the non-ILM peeling and the ILM peeling groups (P = 0.001, P = 0.000). Mean central macular thickness (CMT) decreased significantly in both groups (P = 0.001, P = 0.001). However, there was a significant difference in postoperative CMT between the two groups (P = 0.025). The mean postoperative CMT was significantly higher in the ILM peeling group than in the non-ILM peeling group. Sixteen eyes (84.2%) in the non-ILM peeling group had a normal foveal contour with a foveal depression on postoperative optical coherence tomography (OCT), while nine eyes (42.9%) in the ILM peeling group had a foveal depression (P = 0.01).

CONCLUSIONS

Postoperative OCT revealed that thickening of the macula with loss of the normal foveal contour was more frequent in the ILM peeling group. However, these morphological differences did not result in functional differences in terms of visual outcome.

Use of autologous whole blood during internal limiting membrane peeling and macular hole surgery is protective for indocyanine green toxicity

OBJECTIVE

To compare indocyanine green (ICG)-assisted internal limiting membrane (ILM) peeling with and without autologous whole blood (WB) protection during macular hole repair surgery.

MATERIAL AND METHODS

We retrospectively reviewed 50 eyes with an idiopathic macular hole. Group 1 contained 22 eyes that underwent ILM peeling with WB protection and group 2 contained 28 eyes that underwent ILM peeling without WB. Anatomic and visual results were compared.

RESULTS

After surgery, macular hole closure was achieved in 96% of the group 1 eyes and in 93% of the group 2 eyes. The preoperative mean best-corrected visual acuity (BCVA) was logarithm of the minimum angle of resolution (logMAR) 0.95 in group 1 and logMAR 0.89 in group 2 (p = .544). The postoperative mean BCVA was logMAR 0.57 in group 1 and logMAR 0.92 in group 2 (p = .017).

CONCLUSION

Macular hole surgery protected with WB facilitates improved visual recovery in ICG-assisted ILM peeling.

In vivo toxicity testing of methyl blue and aniline blue as vital dyes for intraocular surgery

PURPOSE

To investigate the biocompatibility of methyl blue and aniline blue as vital dyes for vitreoretinal surgery in an in vivo rat model and to evaluate the effect of these dyes on retinal structure and function.

METHODS

Adult Brown-Norway rats received intravitreal injections of 0.1%, 0.2%, and 2% methyl blue or aniline blue dissolved in balanced salt solution with balanced salt solution serving as a control. Retinal toxicity was assessed 7 days thereafter by means of retinal ganglion cell counts, light microscopy, and electroretinography.

RESULTS

No significant decrease in retinal ganglion cell counts at concentrations up to 0.2% was observed. At 2%, however, a significant retinal ganglion cell loss was detected with both dyes (more pronounced for aniline blue). Light microscopy showed no structural changes in the central retina for concentrations up to 0.2%. Electroretinographies detected no adverse effects of methyl blue or aniline blue on rod- or cone-driven responses at concentrations up to 0.2%.

CONCLUSION

Methyl blue and aniline blue are very biocompatible and may, therefore, be usable for intraocular surgery. Further testing with other animal models will be necessary to confirm this. The safety margin of methyl blue is possibly higher than that of aniline blue.

Value of internal limiting membrane peeling in surgery for idiopathic macular hole and the correlation between function and retinal morphology

Idiopathic macular hole is characterized by a full thickness anatomic defect in the foveal retina leading to loss of central vision, metamorphopsia and a central scotoma. Classic macular hole surgery consists of vitrectomy, posterior vitreous cortex separation and intraocular gas tamponade, but during the past decade focus has especially been on internal limiting membrane (ILM) peeling as adjuvant therapy for increasing closure rates. With increasing use of ILM peeling and indocyanine green (ICG) staining, which is used for specific visualization of the ILM, concerns about the safety of the procedure have arisen. At present, it is not known whether ICG-assisted ILM peeling potentially reduces the functional outcome after macular hole surgery. The purpose of the present PhD thesis was to examine whether ICG-assisted ILM peeling offers surgical and functional benefit in macular hole surgery. We conducted a randomized clinical trial including 78 pseudophakic patients with idiopathic macular hole stages 2 and 3. Patients were randomly assigned to macular hole surgery consisting of (i) vitrectomy alone without instrumental retinal surface contact (non-peeling), (ii) vitrectomy plus 0.05% isotonic ICG-assisted ILM peeling or (iii) vitrectomy plus 0.15% trypan blue (TB)-assisted ILM peeling. Morphologic and functional outcomes were assessed 3, 6 and 12 months after surgery. The results show that surgery with ILM peeling, for both stages 2 and 3 macular holes, is associated with a significantly higher closure rate than surgery without ILM peeling (95% versus 45%). The overall functional results confirm that surgery for macular hole generally leads to favourable visual results, with two-thirds of eyes regaining reading vision (>or=20/40). Macular hole surgery can be considered a safe procedure with a low incidence of sight-threatening adverse events; the retinal detachment rate was 2.2%. Visual outcomes in eyes with primary hole closure were not significantly different between the intervention groups; however, for the stage 2 subgroup with primary macular hole closure, there was a trend towards a better mean visual acuity in the non-peeling group (78.2 letters) compared to the ICG-peeling group (70.9 letters), p = 0.06. Performing repeated macular hole surgery was associated with a significant reduction in functional outcome indicating that primary focus should be on closing the macular hole in one procedure. Morphological studies of closed macular holes with contrast-enhanced optical coherence tomography (OCT) found thinning and discontinuity of the central photoreceptor layer matrix that were highly specific for predicting the likelihood of an eye having regained reading vision 12 months after macular hole surgery. Additionally, healing after macular hole surgery appeared to begin with the contraction of the inner aspect of the retina, forming a roof over a subfoveal fluid-filled cavity, and to end with a gradual restoration of the anatomy in the outer layers of the retina at the junction of the photoreceptor inner and outer segments. We found the more intact this structure was on contrast-enhanced OCT 3 months after macular hole surgery, the better the visual acuity after 12 months, whereas late rather than early resolution of subfoveal fluid had no impact on final visual outcome. The use ILM peeling and intraoperative dyes did not have any functionally important effects on postoperative macular structure. Based on the above findings, we conclude that ILM peeling should be performed in all cases of full thickness macular hole surgery. The use of 0.05% intraoperative isotonic ICG with short exposure time appears to be a safe alternative in stage 3 macular hole surgery, whereas a slight reduction in functional potential not can be excluded when performing 0.05% isotonic ICG-assisted ILM peeling in stage 2 macular hole surgery.

Effects of Indocyanine green on cultured retinal ganglion cells in-vitro

Background

Indocyanine green (ICG) dye is commonly used to stain the inner limiting membrane during macular surgery. There are reports documenting the toxicity of ICG on retinal pigment epithelial cells, with conflicting results in retinal ganglion cells. In the present study, we evaluated the effect of ICG on retinal ganglion cells in vitro.

Cultured rat retinal ganglion cells (RGC-5) were exposed to different concentrations of ICG (0.25, 0.5, 1.0, 1.25, & 5 mg/ml) and at various time intervals (1, 5, 15, 30, & 60 minutes). Changes in structural morphology were identified using phase contrast bright field microscopy. Cell viability was quantified using the neutral red assay and cell death was characterized using Annexin-V staining.

Findings

Significant morphologic changes were observed at the 15 and 60 min intervals for all concentrations, where a reduction in cell size and loss of normal spindle shape was noted. A dose dependent decrease in cell viability was observed with increasing concentration of ICG as well as increasing exposure intervals. Compared to control, 48-74% reduction in neutral red uptake at all concentrations for exposures 5 min or greater (p < 0.001). Even at 1 min exposure, a dose dependent decline was observed in cell viability, with a 28-48% decline for doses above 1.25 mg/ml (p = 0.007). Staining with Annexin-V, demonstrated a similar dose and time dependent increase in number of cells exhibiting early apoptosis. A greater than two-fold increase in Annexin-V expression for all doses at exposures greater than 1 min was noted.

Conclusion

ICG dye exhibits toxicity to retinal ganglion cells at clinically relevant doses following 1 min exposure.

[Vital dyes in vitreoretinal surgery. Current application concepts]

This article reviews the most relevant vital dyes and adjuncts currently available for use in vitreoretinal surgical procedures. The current concepts of intraocular application as well as the staining properties are described, and the issue of biocompatibility is discussed.

Staining and Peeling of the Internal Limiting Membrane in the Cat Eye

PURPOSE

To investigate the cat vitreomacular interface using trypan blue (TB) and indocyanine green (ICG) and to determine the validity of the cat model in terms of staining and peeling of the internal limiting membrane (ILM).

METHODS

Lensectomy and vitrectomy were performed in four eyes of two cats. The ILM of two eyes was stained with TB (0.15%). ILM peeling was performed in one eye. Two eyes were stained with ICG (0.5%). One eye was illuminated for 3 min. Light and transmission electron microscopy and confocal microscopy were performed.

RESULTS

Clinically, both dyes stained the cat ILM similar to human ILM. TB staining resulted in a normal ultrastructure and antigenity of the retina. ILM peeling was associated with intraretinal bleeding. There were fragments of Müller cells adherent to the retinal side of the ILM, and Müller cell endfeet were ruptured and avulsed. ICG staining of the ILM followed by illumination caused severe inner retinal damage. ICG without illumination resulted in focal ILM detachments associated with tearing of Müller cell endfeet.

CONCLUSIONS

The cat can be used as a model to study the effect of TB and ICG on the central area of the cat retina, as previous results from clinical and experimental postmortem settings in human eyes were confirmed in the current study. Peeling of the ILM as a sheet as performed in human macular surgery is not feasible. Differences in the ultrastructure of the ILM and a strong adhesion of the ILM to Müller cell endfeet may account for this observation.

Toxicity of Indocyanine Green (ICG) in Combination with Light on Retinal Pigment Epithelial Cells and Neurosensory Retinal Cells

PURPOSE

To evaluate the toxicity of indocyanine green (ICG) in combination with light.

METHODS

Human retinal pigment epithelial cells (ARPE-19) and rat neurosensory retinal cells (R28) were treated with four different concentrations of ICG in combination with light exposure. Cell viability, mitochondrial function, and DNA synthesis were measured.

RESULTS

All concentrations of ICG with 10 min of light exposure caused a significant decrease in mitochondrial dehydrogenase activity in R28 and ARPE-19 cells. ICG without light exposure did not decrease mitochondrial dehydrogenase activity. In both cell lines, [(3)H]thymidine incorporation was increased when treated with ICG with or without light. R28 cells did not show any significant decrease in cell viability.

CONCLUSIONS

The duration of light was a significant factor in ICG toxicity. ICG needs to be used with caution as it decreases the mitochondrial dehydrogenase activity and increases the DNA synthesis in retinal cells, markers for cell toxicity and dysfunction.

Blood-assisted internal limiting membrane peeling for macular hole repair

PURPOSE

To evaluate the efficacy of autologous heparinized whole blood in assisting internal limiting membrane (ILM) peeling by coating the ILM for macular hole (MH) repair.

DESIGN

Prospective, interventional case series.

PARTICIPANTS

Twenty-nine patients (32 eyes) who underwent blood-assisted ILM peeling for MH repair.

METHODS

Patients in whom stage 2-4 idiopathic MHs had developed and who desired surgery were enrolled in this study. After core vitrectomy, autologous heparinized whole blood was applied to cover the macula and to coat the surface of the macular area in the fluid-filled vitreous cavity. The redundant blood was removed and only a very thin film of blood was left on the macular area. The blood-coated ILM was removed by forceps in a circular fashion. To confirm the removed membrane was the ILM, the first 10 specimens were examined by electron microscopy (EM).

MAIN OUTCOME MEASURES

The MH closure rate, the interval mean visual acuity (before and after surgery), retinal changes, and the EM results of the ILM specimens.

RESULTS

All 32 eyes in 29 patients completed 12 months of follow-up. The ILM were coated by autologous heparinized whole blood, removed without difficulty, and confirmed by EM. The whole blood highlighted the contrast of the coated and noncoated areas during the ILM peeling procedure. The MHs were closed in all surgical eyes with a single surgery (100%). Compared with study entry, the mean logMAR best-corrected visual acuity 12 months after surgery improved significantly (1.02 and 0.53, respectively; P<0.001). At 12 months of follow-up, 31 eyes (96.9%) had stable or improved vision. No toxic fundus changes were observed during follow-up.

CONCLUSIONS

Autologous heparinized whole blood coated the ILM and facilitated visibility during ILM peeling. Autologous heparinized whole blood is a cost-effective and useful tool for assisting MH surgery.

Should Indocyanine green should be used to facilitate removal of the internal limiting membrane in macular hole surgery

Indocyanine green (ICG) is one of several vital dyes that are used in vitreoretinal surgery to aid visualization of diaphanous collagenous tissues in what has been called chromovitrectomy. As shown herein, much has been written about the use and rather narrow safety profile of ICG. The discussion surrounding its applications would have ended long ago were it not for the occasional patient who keeps returning to the office with permanent central scotomas after ICG-assisted macular hole surgery. The purpose of this Viewpoint is to reemphasize potential methods of proper use and clarify safety issues of this particular vital dye that enhances surgical technique but not necessarily visual outcome.

Viscoelastic agent retention and failed macular hole surgery

PURPOSE

To describe the retention of a viscoelastic agent as a possible cause of failed macular hole surgery.

METHODS AND PATIENTS

Three consecutive patients underwent macular hole surgery. A bubble of viscoelastic agent was used to prevent contact between indocyanine green dye and retinal pigment epithelium cells.

RESULTS

Macular hole repair failed in all three cases. After a second surgery the holes closed successfully.

CONCLUSION

The use of a dispersive viscoelastic agent to avoid indocyanine green toxicity in macular hole surgery may prevent the closure of the hole.

Analysis of the neuronal marker protein gene product 9.5 in internal limiting membranes after indocyanine-green assisted peeling

BACKGROUND

Indocyanine green-assisted internal limiting membrane (ILM) peeling was suspected to disrupt the innermost layer of the neural retina. We examined whether surgically excised specimens contain remnants of neuronal tissue.

METHODS

Ten patients with macular hole underwent pars plana vitrectomy and indocyanine green-assisted ILM peeling. A total of 0.1 mL of a 0.5% indocyanine green solution was applied for 15 seconds. The ILM specimens were prepared for immunohistochemistry, using a polyclonal antibody against protein gene product 9.5. Protein gene product 9.5 is a pan-neuronal marker labeling human neuronal cells. Appropriate controls to show selectivity of the antibody were performed on neuronal tissue of donor eyes. One ILM was prepared for electron microscopy.

RESULTS

A selective expression of protein gene product 9.5 was found in neuronal fibers of the retina and optic nerve of donor eyes. Only 1 of the 10 surgical ILM specimens showed a minimal focal positivity for protein gene product 9.5. No neuronal tissue was detected on the ILM by electron microscopy.

CONCLUSION

Focal expression of protein gene product 9.5 in only 1 of 10 surgical ILM specimens argues against a general indocyanine green-related disruption of the innermost retinal layers. However, higher concentrations of the dye, longer incubation times or different solvents than used in this study may lead to different results.

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.

Macular hole surgery with triamcinolone acetonide-assisted internal limiting membrane peeling: one-year results

PURPOSE

To report the 1-year results of macular hole surgery with triamcinolone acetonide (TA)-assisted internal limiting membrane (ILM) peeling and to compare those with results of indocyanine green (ICG)-assisted ILM peeling.

METHODS

In a nonrandomized, retrospective, interventional case series, 40 eyes of 39 consecutive patients with idiopathic full-thickness macular holes underwent macular hole surgery with TA-assisted ILM peeling. Surgical results 1 year after surgery, including changes in best-corrected visual acuity (BCVA) and macular hole closure, were evaluated. Moreover, we compared the results for these 40 eyes (TA group) with those for 27 eyes of 27 consecutive patients who had undergone macular hole surgery with 0.25% ICG-assisted ILM peeling (ICG group).

RESULTS

In the TA group, macular holes were closed in 39 (98%) of 40 eyes. Mean BCVA +/- SD significantly improved from 0.78 +/- 0.31 logarithm of the minimal angle of resolution (logMAR) preoperatively to 0.20 +/- 0.30 logMAR (P < 0.001). BCVA improved by > or =0.2 logMAR in 37 eyes (93%). BCVA was 20/40 or better in 33 (83%) of 30 eyes. In the ICG group, macular holes were closed in all 27 eyes (100%), and mean BCVA +/- SD significantly improved from 0.81 +/- 0.4 logMAR preoperatively to 0.34 +/- 0.2 logMAR 1 year postoperatively (P < 0.001). BCVA improved by > or =0.2 logMAR in 22 eyes (81%). BCVA was 20/40 or better in 16 (59%) of 27 eyes. Significant differences between groups were seen in mean BCVA 1 year after surgery (P = 0.049) but not in BCVA of 20/40 or better (P = 0.17) or change in BCVA by > or =0.2 logMAR (P = 0.05).

CONCLUSION

TA is useful as an adjuvant for ILM peeling in macular hole surgery, and BCVA 1 year after surgery might be more favorable when compared with ICG-assisted ILM peeling.

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.

Residual indocyanine green fluorescence pattern after vitrectomy with internal limiting membrane peeling in high myopia

PURPOSE

The use of indocyanine green (ICG) during intraoperative internal limiting membrane (ILM) peeling is common for various macular diseases. The authors observed residual ICG after vitrectomy for high myopia-related macular diseases and found a unique pattern specific to its pathologic features.

DESIGN

Observational case series.

METHODS

Twelve eyes of 12 patients with high myopia who had undergone vitrectomy with ICG-assisted ILM peeling were included (macular hole [MH], six eyes; MH and retinal detachment, three eyes; and myopic foveoschisis, three eyes). Patterns of residual ICG were observed in the posterior retina using the Heidelberg Retina Angiograph 2 (Heidelberg Engineering, Heidelberg, Germany) after surgery and were compared. The minimum follow-up was six months. Two control eyes of two patients without intravitreal ICG also were included in this study.

RESULTS

The residual ICG fluorescence was observed in all eyes except for the control eyes. The pattern of residual ICG fluorescence depended on the degree of myopic chorioretinal atrophy. In eyes with no or minimum chorioretinal atrophy, the pattern was similar to that of an idiopathic MH. The ICG pattern was unique in those with moderate or severe atrophy. A strong ICG signal was observed at the area of diffuse atrophy and at the edge of the patchy atrophy and staphyloma. No ICG fluorescence was observed inside the patchy atrophy.

CONCLUSIONS

Residual ICG fluorescence was observed in high myopia. ICG accumulation seems to depend on the status of the retinal pigment epithelial (RPE) underlying the posterior retina. RPE cells may play an important role in the kinetics of the residual ICG.

PREVENTING THE DEPOSITION OF TRIAMCINOLONE IN MACULAR HOLE BY USE OF WHOLE BLOOD IN TRIAMCINOLONE-ASSISTED MEMBRANE PEELING

PURPOSE

To prevent triamcinolone acetonide (TA) deposition in the macular hole by use of whole blood during TA-assisted internal limiting membrane (ILM) peeling.

METHODS

The prospective, interventional case series study included 18 consecutive idiopathic macular holes (18 patients) that underwent TA-assisted internal limiting membrane (ILM) peeling for macular hole treatment. After core vitrectomy, autologous whole blood was applied to cover the macular hole. Pre-prepared TA solution was gently injected onto the macular area. Residual TA particles were removed after ILM peeling. Closure rate of macular hole, preoperative and postoperative median visual acuity, and retinal changes were evaluated.

RESULTS

Autologous whole blood prevented the deposition of TA particles in the macular hole. The ILM could be recognized after TA-assisted visualization for removal. Average follow-up time was 8.6 months. The hole was closed with one surgery in 17 eyes (94%); visual acuity improved in 15 eyes (83%). Preoperative median best-corrected visual acuity was 20/100 (range = 20/400-20/50). Postoperative median best-corrected visual acuity was 20/40 (range = counting fingers-20/20).

CONCLUSIONS

Whole blood can prevent TA particle deposition in the macular hole. Potential toxicity of TA on retinal pigment epithelium and retina also may be reduced.

The Effect of ICG on Mitomycin C Cytotoxicity in Human Tenon Fibroblasts

PURPOSE

To examine the effects of indocyanine green (ICG) with and without mitomycin C (MMC) on proliferation of cultured human Tenon fibroblasts.

METHOD

Fibroblast monolayers were exposed to either MMC [0.4 mg/mL in phosphate buffered saline (PBS)] or PBS containing ICG (0.0625%, 0.125%, 0.25%, and 0.5% in 200 microL PBS) or a combination of MMC (0.4 mg/mL in PBS) and ICG (0.25% and 0.5%) for 5 minutes. Controls were exposed for 5 minutes to MMC, PBS, or culture medium containing no ICG. After treatment, the monolayers were washed and incubated in culture medium for 24, 48, 72 hours, and 1 week periods after which the number of viable cells was quantified.

RESULTS

The presence of ICG alone, at concentrations ranging from 0.0625% to 0.5%, had no effect on the rate of fibroblast proliferation measured at any of the incubation periods. As expected, MMC treatment resulted in a significant reduction in viable fibroblast number (8.4+/-0.13x10(3)). ICG in combination with MMC did not significantly alter fibroblast numbers (8.5+/-0.05x10(3)) up to 1 week compared with MMC alone (8.4+/-0.12x10(3)).

CONCLUSIONS

ICG at concentrations of 0.5% and below do not reduce proliferation of Tenon capsule fibroblasts. ICG did not potentiate or diminish the effect of MMC on Tenon capsule fibroblast proliferation.

Surgical effects and complications of indocyanine green-assisted internal limiting membrane peeling for idiopathic macular hole

PURPOSE

To compare the surgical outcomes and complications of vitrectomy with internal limiting membrane (ILM) peeling with or without indocyanine green (ICG) staining in eyes with an idiopathic macular hole.

METHODS

This study involved a non-randomized, single-centre, retrospective, interventional case series. Rates of anatomical closure, visual acuities (VAs) and postoperative complications in 35 eyes of 31 patients who underwent ICG-assisted ILM peeling during macular hole surgery (stained group) were compared with those in 18 eyes of 16 patients who underwent the same procedure without ICG staining (non-stained group).

RESULTS

Macular holes were closed following the initial surgery in 97% of the stained group and 94% of the non-stained group (p > 0.999). There was no significant difference in mean final VA between the stained and non-stained groups, but there was a lower percentage of eyes with postoperative vision > 20/25 in the stained group (15%) than in the non-stained group (44%) after 2 years (p = 0.036). Posterior retinal pigment epithelium atrophy, retinoschisis and visual field defects were observed only in the stained group.

CONCLUSIONS

The difference in mean final VA between the two groups was not significant. However, a lower percentage of eyes obtained VA > or = 20/25 and a higher incidence of postoperative complications occurred in the stained group. These results indicate that some consideration should be made before ICG is used in macular hole surgery.

Long-term clinical outcomes and therapeutic benefits of triamcinolone-assisted pars plana vitrectomy for proliferative vitreoretinopathy: a case study

PURPOSE

To investigate intraoperative visibility and long-term clinical outcome following triamcinolone acetonide (TA)-assisted pars plana vitrectomy (PPV) for proliferative vitreoretinopathy (PVR).

METHODS

A retrospective interventional noncomparative clinical study was carried out on 21 eyes from 21 patients with more than grade C2 PVR, all of whom underwent TA-assisted PPV. Two of the specimens were observed with an electron microscope. After treatment, outcome measures, including changes in best-corrected visual acuity (BCVA), intraocular pressure (IOP) elevation, corneal pathology, and occurrence of endophthalmitis, were recorded. Patient follow-up time was >36 months (mean +/-standard deviation = 47.3 +/- 6.7 months).

RESULTS

TA improved the intraoperative visualization of the epiretinal membrane (ERM), allowing it to be easily removed together with the partially internal limiting membrane (ILM) using micro forceps. The excised tissue consisted of proliferative cells and an extracellular matrix underlying the ILM. After the operation, 71.4% of the eyes had improved BCVA. Three of the eyes showed sustained IOP elevation (14.3%); two of these cases were controlled by the administration of eyedrops, while the third required filtering surgery. In two cases, an absorption delay of the TA granule on the retinal surface was observed. One eye developed corneal stromal opacity. No other severe complications occurred during the observation period.

CONCLUSIONS

TA-assisted PPV offers improved visualization during the surgical management of PVR, and allows surgeons to excise the ERM safely and effectively without the risk of serious complications.

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.

Effects of Subretinal Injections of Indocyanine Green, Trypan Blue, and Glucose in Rabbit Eyes

PURPOSE

To evaluate the effects of subretinal injections of indocyanine green (ICG), trypan blue, glucose (GL), and balanced salt solution (BSS) in rabbits.

DESIGN

Experimental study.

PARTICIPANTS

Twenty Dutch-belted rabbits.

METHODS

Ten animals underwent vitrectomy and subretinal injection of 0.02 ml of either 0.05% ICG (279 milliosmoles [mOsm]), 0.15% trypan blue (312 mOsm), 5% GL (280 mOsm), or BSS (300 mOsm), which was tested as a control. Ten additional animals underwent subretinal injection of 0.02 ml of 0.046% ICG (251 mOsm), 0.13% trypan blue (260 mOsm), 4.6% GL (253 mOsm), or BSS (300 mOsm). Animals were examined 6, 12, and 24 hours and 14 days after the procedure by fluorescein angiography and fundus evaluation; histologic studies were performed by light and transmission electron microscopy.

MAIN OUTCOME MEASURES

Clinical outcome, fluorescein angiography, and histopathologic results.

RESULTS

All subretinal blebs were flat 24 hours after the procedure. Fluorescein angiography showed window defects where ICG and trypan blue had been injected. Subretinal BSS and GL resulted in minimal abnormalities of the photoreceptor outer segments (POS) during follow-up. Hypo-osmolar GL caused edema in all retinal layers; pyknosis of the outer nuclear layer (ONL) was observed 24 hours after injection. Subretinal injection of trypan blue resulted in histologic abnormalities 24 hours and 14 days after surgery. Hypo-osmolar trypan blue caused edema of the POS and the photoreceptor inner segments and pyknosis of the ONL 6 and 12 hours after surgery; the retinal pigment epithelium also was affected 24 hours and 14 days after surgery. Subretinal injection of iso-osmolar and hypo-osmolar ICG caused severe damage of all retinal layers during the entire follow-up.

CONCLUSIONS

Subretinal injection of 0.05% ICG results in more substantial retinal damage than that associated with the 0.15% trypan blue subretinal injection. The damage induced by hypo-osmolar solutions was more important than that caused by the iso-osmolar solutions. These findings emphasize that care must be taken regarding the solution osmolarity and that subretinal migration of these substances should be avoided during macular hole surgery.

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.

Hypothermia Protects Cultured Human Retinal Pigment Epithelial Cells against Indocyanine Green Toxicity

PURPOSE

The aim of this study was to determine whether indocyanine green (ICG) is toxic to cultured human retinal pigment epithelial (ARPE-19) cells, and whether hypothermia can protect the ARPE-19 cells against the ICG toxicity.

METHODS

Cultured ARPE-19 cells were exposed to 0.25, 0.5, 1, 2.5, and 5 mg/mL of ICG dye at 37 and 4 degrees C for 30 min. The percentage of ARPE-19 cells that survived was determined by resazurin 1 day after the exposure.

RESULTS

Exposure of the RPE cells to a hypotonic saline solution with an osmolarity equal to 5 mg/mL of ICG did not induce a statistically significant decrease in the percentage of RPE cells that survived. Exposure of the ARPE-19 cells to ICG induced a significant decrease in the percentage of cell survival at all concentrations of ICG (P<0.05), except in 0.25 mg/mL at 37 degrees C. At 4 degrees C, on the other hand, ICG induced a statistically significant decrease in the percentage of RPE cell survival only at 5 mg/mL of ICG (P<0.05).

CONCLUSIONS

These results indicate that ICG is toxic to human RPE cells in culture, and that cell death cannot be attributed to the low osmolarity. Hypothermia of 4 degrees C has a protective effect against ICG toxicity.