Comparison of the in vitro safety of intraocular dyes using two retinal cell lines: a focus on brilliant blue G and indocyanine green

Stainability of Acrylic Intraocular Lens With Brilliant Blue G: An In Vitro Study

PURPOSE

To evaluate the stainability of several acrylic intraocular lens (IOLs) with Brilliant Blue G (BBG) in vitro.

DESIGN

Clinically relevant, laboratory, experimental study.

METHODS

LS313MF15 as a hydrophilic acrylic IOL and X-70, W60R, CP2.2R, YP2.2R, XC1, and XY1 as hydrophobic acrylic IOLs were included in this study. Prepared acrylic IOLs were evaluated for staining via immersion for different periods in BBG solution with adjusted concentrations. In cases where IOLs were stained blue, the sustained release of BBG and IOL cross-sectional images were evaluated, as well as changes in the optical properties of the IOLs via spectrophotometry.

RESULTS

All acrylic IOLs were stained with BBG in a BBG concentration- and staining time-dependent manner, with almost no sustained release of BBG observed. Lenses with a higher water content exhibited more pronounced staining, and BBG penetrated into the IOLs. A decrease in light transmittance with a peak wavelength of 610 to 620 nm was observed in blue-stained IOLs. LS313MF15 was markedly blue stained even with a short period of staining.

CONCLUSIONS

Any acrylic IOL can be stained with BBG, but hydrophilic IOLs are particularly susceptible to blue staining. Precautions should be taken in surgeries requiring the use of BBG staining, and efforts should be made to ensure that BBG components are sufficiently washed out intraoperatively.

The application of indocyanine green in guiding prostate cancer treatment

Objective

Indocyanine green (ICG) with near-infrared fluorescence absorption is approved by the United States Food and Drug Administration for clinical applications in angiography, blood flow evaluation, and liver function assessment. It has strong optical absorption in the near-infrared region, where light can penetrate deepest into biological tissue. We sought to review its value in guiding prostate cancer treatment.

Methods

All related literature at PubMed from January 2000 to December 2020 were reviewed.

Results

Multiple preclinical studies have demonstrated the usefulness of ICG in identifying prostate cancer by using different engineering techniques. Clinical studies have demonstrated the usefulness of ICG in guiding sentinel node dissection during radical prostatectomy, and possible better preservation of neurovascular bundle by identifying landmark prostatic arteries. New techniques such as adding fluorescein in additional to ICG were tested in a limited number of patients with encouraging result. In addition, the use of the ICG was shown to be safe. Even though there are encouraging results, it does not carry sufficient sensitivity and specificity in replacing extended pelvic lymph node dissection during radical prostatectomy.

Conclusion

Multiple preclinical and clinical studies have shown the usefulness of ICG in identifying and guiding treatment for prostate cancer. Larger randomized prospective studies are warranted to further test its usefulness and find new modified approaches.

Membrane Blue Dual Protects Retinal Pigment Epithelium Cells/Ganglion Cells-Like through Modulation of Mitochondria Function

Although recent data highlight the greater protective effects exerted by Membrane Blue Dual (MBD), a precise analysis of the mechanisms of action is missing. We examined the effects of MBD with/without polyethylene glycol (PEG) on both human retinal pigment epithelial cells (ARPE-19) and retinal ganglion cells-like (RGC-5) cultured in the presence/absence of ultraviolet B (UVB) treatment on mitochondria function, oxidants, and apoptosis. In ARPE-19/RGC-5 cells either treated or not with UVB, the effects of MBD with/without PEG were evaluated by specific assays for viability, mitochondrial membrane potential and mitochondrial reactive oxygen species (mitoROS) release. Annexin V was used to detect apoptosis, whereas trypan blue and the scratch assay were used for proliferation/migration. In both physiologic conditions and in the presence of UVB, MBD with/without PEG increased cell viability, mitochondrial membrane potential, proliferation and migration in both ARPE-19 and RGC-5 cells. In general, the effects of MBD with PEG were greater than those caused by MBD without PEG. Our results suggest that, in particular, MBD with PEG is a safe and effective dye for vitreoretinal surgery through the modulation of mitochondrial function.

Brilliant Blue G toxicity in macular hole surgeries: A report on combined phototoxicity and dye-induced macular damage

Purpose: Vitrectomy with brilliant blue G (BBG) assisted internal limiting membrane (ILM) peeling is the standard operational technique in macular hole surgeries. However, BBG dye, though considered safe and nontoxic, can also occasionally lead to macular toxicity. This study aims to describe the clinical features and characteristics of four eyes who developed macular toxicity after following surgery for macular hole repair.Methods: Retrospective review of four consecutive cases of macular toxicity after conventional BBG assisted ILM peeling. All the cases reviewed, their operative surgical notes were retrieved and analyzed. The ILM was stained twice during surgery with prolonged intraoperative surgical time.Results: All four cases had a prolonged surgical time and the ILM was stained twice during surgery in all cases. The area of macular toxicity was corresponding to the area of ILM peeling which had been exposed to repeated staining by BBG dye. By the end of one month, all four cases had foveal thinning along with choriocapillary atrophy. The mean BCVA was 20/80 before surgery and the final mean visual acuity was <20/800.Conclusion: This report highlights the occurrence of macular and choriocapillary atrophy due to prolonged focal endoillumination and the increased risk of toxicity with repeated dye staining.

Rates of Reoperation in 10 114 Patients with Epiretinal Membranes Treated by Vitrectomy with or without Inner Limiting Membrane Peeling

PURPOSE

To compare rates of reoperation in patients with idiopathic epiretinal membrane (ERM) who received pars plana vitrectomy (PPV) with or without inner limiting membrane (ILM) peeling and to assess trends in the overall use of ILM peeling over time.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Patients included in the IBM Marketscan database between January 1, 2008, and December 31, 2016, who underwent surgery for idiopathic ERM.

METHODS

Procedure claims with laterality codes were used to determine patients with idiopathic ERM who received PPV with or without ILM peel between 2008 and 2016, and to identify cases of reoperation and subsequent retinal detachment within 1 year of index surgery.

MAIN OUTCOME MEASURES

The primary outcome was rate of reoperation for recurrent ERM according to whether or not patients receive an ILM peel during their index ERM surgery. We also assessed trends for index ERM surgery (ILM peel or no ILM peel) between 2008 and 2016, and the risk of developing retinal detachment within 1 year of the index ERM surgery.

RESULTS

A total of 10 114 patients received ERM surgery and met inclusion criteria (5310 without ILM peel and 4804 with ILM peel). The reoperation rate was significantly lower among patients who received PPV with ILM peel (0.88%) compared with patients without ILM peel (1.48%; P = 0.007). In 2008, PPV without ILM peel represented 70% of ERM procedures, but PPV with ILM peeling accounted for 52% and 70% of ERM procedures in 2013 (P < 0.001) and 2016 (P < 0.001), respectively. The rates of retinal detachment were similar between patients who received an ILM peel (0.79%) and patients who did not receive an ILM peel (0.92%) during their primary ERM surgery (P = 0.474).

CONCLUSIONS

The increasing use of PPV with ILM peeling to address ERM removal is associated with significantly reduced reoperation rates within 1 year. Future studies are needed to determine the cost-effectiveness of performing an ILM peel for initial idiopathic ERM repairs and evaluate long-term visual and structural changes related to ILM peeling.

Comparative effects of commonly used intraocular dyes on the viability of human retina Müller cells

This study investigated the in vitro effect of various vital dyes in common clinical use on human Müller cell viability, and it compared the toxicity of these dyes using a cell culture model. Müller cells were exposed to a series of concentrations (1 %, 0.5 %, 0.25 %, and 0.125 % or 12.9 mM, 6.45 mM, 3.22 mM and 1.61 mM) of Indocyanine green (ICG) for 2, 24, 48, and 72 h. Similarly, groups of Müller cells were stained with "Heavy" brilliant blue G (HBBG), Trypan blue (TB) (0.15 %, or 1.56 mM), Membrane-blue-dual (MBD), and ICG (0.25 %, or 3.22 mM) or BBG (0.025 %, or 0.3 mM) with glucose (GS) (50 %, 66 % and 75 % or 2.78 M, 3.67 M and 4.17 M) for 30, 60, and 120 s. Cell viability was measured with the Cell Counting Kit-8 (CCK-8) and Lactate Dehydrogenase (LDH) release assays. We found that high stain concentration and long exposure time resulted in increased toxicity to Müller cells. Nevertheless, ICG seemed to be safe at the clinically relevant concentration of 0.25 % (3.22 mM) in the short time of exposure. TB was safer than both HBBG and MBD, especially HBBG. Hypertonic GS as a dilution was not safe for Müller cells, and the negative effect was more obvious in 0.025 % (0.3 mM) BBG than that in 0.25 % (3.22 mM) ICG. This is the first report to observe the cytotoxicity of commonly used stains in clinical on human Müller cells in vitro, and to provide some basis for further studies, including in vivo investigation.

Effect of brilliant Blue-G on cellular stress response in retinal pigment epithelial cells: In vitro

To assess the cellular stress evoked by exposure of Brilliant Blue-G (BBG), adult retinal pigment epithelial (ARPE-19) cells were treated with various dilutions of BBG in balanced salt solution plus (BSS-PLUS) with and without endoillumination (Alcon Constellation Vision System). The treatments lasted for acute periods of 2 and 5 min. MTT and presto blue assays were performed to assess the changes in cell viability; reactive oxygen species (ROS) production was quantified by DCFDA (dichlorofluorescin diacetate) assay, and the expression of inflammatory stress and endoplasmic reticulum (ER) genes were quantified by qPCR. We observed no reduction in cell viability at 2 min of dye treatment with and without endoillumination while at 5 min exposure, a reduction in cell viability at all concentrations of the dye was observed compared to control. Though there was an increase in ROS with endoillumination, it was insignificant. There was no change in the mRNA expression of TNF-α while that of GRP78, and inflammatory genes viz. IL-8, IL-1β showed a significant increase at 0.5 mg/ml dye with endoillumination. BBG reduced cell viability with increasing concentration and time. The undiluted concentration of the dye results in inflammatory stress compared to the diluted formulations. Interestingly, increased GRP78 at undiluted concentration indicates a protective response in cells exposed to light. However, further studies are needed to evaluate the effect of cellular stress on the visual outcome. We infer that the commercially available formulation of BBG is safe for the RPE, at the recommended dose for a short duration however its toxicity to other cell types need to be addressed.

A new dye based on anthocyanins from the acai fruit (Euterpe oleracea) for chromovitrectomy in humans: clinical trial results

PURPOSE

To test the applicability of the acai dye at a 25% concentration for identifying the posterior hyaloids and internal limiting membranes (ILMs) during pars plana vitrectomy (PPV) in human eyes with macular holes (MHs).

METHODS

This study included 25 patients with chronic idiopathic MHs. The exclusion criteria included glaucoma, previous significant ocular conditions, and previous ocular surgeries except uncomplicated cataract. Ten surgeons performed 23-gauge four-port PPV, phacoemulsification, posterior hyaloid detachment, ILM peeling guided by dye staining, and perfluoropropane injection. The patients remained prone for 5 days postoperatively. The patients were evaluated postoperatively after 1, 30, and 180 days. The surgeons completed a questionnaire regarding the dye's staining abilities.

RESULTS

The posterior hyaloids and ILMs stained purple in all eyes. The final best-corrected visual acuity improved significantly (p < 0.001) from preoperatively (1.37 ± 0.29) to 180 days postoperatively (1.05 ± 0.43). The MHs closed in 76% of eyes.

CONCLUSION

The acai dye at a 25% concentration identified posterior hyaloids and ILMs during PPVs in humans. Dye toxicity was unlikely.

New Vital Dye Injection Technique With Vitrectomy Probe

BACKGROUND AND OBJECTIVE

To evaluate a new, safer way to inject vital dye during chromovitrectomy for dye-assisted macular peeling.

PATIENTS AND METHODS

Prospective consecutive case series. Enrolled patients underwent macular surgery with a new technique of staining the epiretinal membrane and the internal limiting membrane with vital dyes. Twenty eyes of 20 patients (eight men, 12 women) were affected by idiopathic epiretinal membrane and underwent 25-gauge via pars plana vitrectomy for epiretinal membrane removal. Ten eyes were stained with Membrane Blue-Dual (Brilliant Blue G + trypan blue; DORC, Zuidland, The Netherlands) and 10 eyes were stained with Brilliant Peel (Brillant Blue G; Fluoron GmbH, Ulm, Germany). Preoperatively and postoperatively (1, 3, and 6 months) all patients received a complete ophthalmologic examination with best-corrected visual acuity (BCVA) assessment, swept-source optical coherence tomography, and multifocal electroretinography (mfERG).

RESULTS

The mean age of the patients was 67.0 years ± 8.6 years (range: 55 years to 78 years). No statistically significant difference in BCVA improvement or central foveal thickness decrease was observed in either group (P > .05). The mfERG showed an increase in electrical response densities 3 months after surgery.

CONCLUSION

The authors describe a new technique to inject vital dye during chromovitrectomy for dye-assisted macular peeling that may help to improve the overall safety of macular surgery. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:528-533.].

Toxicity and phototoxicity in human ARPE-19 retinal pigment epithelium cells of dyes commonly used in retinal surgery

PURPOSE

To compare, for the first time, systematically the toxicity and phototoxicity of dyes and dye combinations used in vitreoretinal surgery. The dyes were trypan blue, brilliant blue G, trypan blue + brilliant blue G, indocyanine green, bromophenol blue, bromophenol blue + brilliant blue G, and acid violet 17, in clinically used concentrations.

METHODS

Human ARPE retinal pigment epithelium cells were exposed to the dyes for 30 min. For phototoxicity, the cells were exposed for 15 min to high-intensity light from a light emitting diode source with an intensity similar to surgical conditions. Toxicity was assayed either directly after exposure to either dye alone or dye and light, or with a delay of 24 h.

RESULTS

None of the dyes or their combinations was toxic when cells were exposed to them at ambient light. Acid violet led to a reduction viability by 90% already immediately after light exposure. Bromophenol blue and its combination with brilliant blue G showed strong phototoxicity (reduction of viability by 83%) when assayed with delay. Indocyanine green with different agents to adjust osmolarity (balanced salt solution, glucose, and mannitol) was not found to be toxic.

CONCLUSION

The strong immediate phototoxicity of acid violet reflects its clinical toxicity. Bromophenol blue might also be disadvantageous for patient outcome because of its delayed phototoxicity. The other dyes (trypan blue, brilliant blue g, and indocyanine green) were not found to be toxic neither with exposure to ambient light nor after exposure to light of intensities used in surgery.

Macular hole surgery: an analysis of risk factors for the anatomical and functional outcomes with a special emphasis on the experience of the surgeon

Purpose

The aim of this study was to evaluate risk factors for the anatomical and functional outcomes of macular hole (MH) surgery with special emphasis on the experience of the surgeon.

Methods

A total of 225 surgeries on idiopathic MHs (IMHs) performed by 6 surgeons with a mean follow-up period of 20.5 months were reviewed in this retrospective study. Outcome parameters focused on IMH closure, complications and visual acuity improvement. The results of MH surgeries performed by experienced surgeons were compared to those of surgeons in training.

Results

The average MH size was 381 µm (standard deviation [SD]=168). Brilliant blue G (BBG) for internal limiting membrane (ILM) staining was used in 109 (48%) eyes and indocyanine green (ICG) in 116 (52%) eyes. As endotamponade, 20% SF6 was used in 38 (17%) cases, 16% C2F6 in 33 (15%) cases and 16% C3F8 in 154 (68%) cases. IMH closure was achieved in 194 eyes (86%). Mean preoperative visual acuity was 0.84 logarithm of the minimum angle of resolution (log MAR; SD=0.29, range: 0.3–1.5); surgery led to a mean improvement of 0.40 (SD=0.37) log MAR. Although the MH closure rate was the same using BBG or ICG for ILM peeling, visual acuity improvement was better in eyes peeled with BBG compared to eyes peeled with ICG (log MAR: BBG: 0.38 [95% CI: 0.32, 0.44] vs ICG: 0.48 [95% CI: 0.42, 0.54], P=0.029). Surgeons with previous experience in vitreoretinal surgery of ≥6 years achieved better visual outcomes compared to surgeons with 0–3 years of experience, regardless of the MH size, preoperative visual acuity, time to follow-up or dye used for ILM peeling (0–3 years [0.27, Δlog MAR] vs ≥6 years [0.43, Δlog MAR], P=0.009).

Conclusion

Our results indicate that vitrectomy with ILM peeling performed by non-experienced surgeons is a safe procedure leading to good anatomical and functional results. Very experienced surgeons may achieve even better functional outcomes.

Retinal Toxicity of Acai Fruit (Euterpe Oleracea) Dye Concentrations in Rabbits: Basic Principles of a New Dye for Chromovitrectomy in Humans

PURPOSE

Evaluate toxicity of acai fruit (Euterpe oleracea) dye concentrations in a rabbit model.

METHODS

Rabbits were injected intravitreously with 10%, 25%, and 35% acai dye concentrations. Control eyes received balanced salt solution (BSS). Electroretinogram (ERG), fundus imaging, fluorescein angiography (FA), optical coherence tomography (OCT), and light and transmission electron microscopy (LM/TEM) were performed.

RESULTS

Fundus imaging showed increased vitreous opacity with increased dye concentrations. FA and OCT showed normality with all concentrations. Comparisons between BSS and dye concentrations were analyzed using Kruskal-Wallis and Mood's median test (p < 0.05). At 24 h, ERGs showed reduced amplitudes from baseline in all eyes. Median b-wave amplitudes nonsignificantly decreased and latency increased with 10% and 25%; findings were significant (p < 0.05) for 35%. LM and TEM showed no abnormalities for 10% and 25%. With 35%, TEM showed ganglion cell edema at 24 h that resolved after 7 days. Vacuolization, multilamellar bodies, and nerve bundle damage occurred at 24 h/7 days in the inner nuclear layer. Mitochondrial cristae disruption occurred in the inner photoreceptor segment at 24 h that decreased by 7 days.

CONCLUSION

Ten and twenty-five percent concentrations were safe and may improve identification of the posterior hyaloid and internal limiting membrane during chromovitrectomy in humans.

Differential autophagic effects of vital dyes in retinal pigment epithelial ARPE-19 and photoreceptor 661W cells

Indocyanine green (ICG) and brilliant blue G (BBG) are commonly used vital dyes to remove internal limiting membrane (ILM) in vitreoretinal surgery. The vital dyes have shown cytotoxic effects in ocular cells. Autophagy is a stress responsive pathway for either protecting cells or promoting cell death. However, the role of autophagy in ocular cells in response to the vital dyes remains unknown. In this study, we found that ICG and BBG reduced cell viability in both human retinal pigment epithelial ARPE-19 and mouse photoreceptor 661W cells. ICG and BBG induced lipidated GFP-LC3-II and LC3-II in ARPE-19 and 661W cells. Combination treatment with the autophagy inhibitor chloroquine indicated that ICG and BBG reduced autophagic flux in ARPE-19 cells, whereas the vital dyes induced autophagic flux in 661W cells. Moreover, genetic and pharmacological ablation of autophagy enhanced vital dyes-induced cytotoxicity in ocular cells. Dietary supplements, including resveratrol, lutein, and CoQ10, induced autophagy and diminished the cytotoxic effects of ICG and BBG in ocular cells. These results suggest that autophagy may protect ARPE-19 and 661W cells from vital dyes-induced damage.

Autologous Internal Limiting Membrane Fragment Transplantation for Large, Chronic, and Refractory Macular Holes

OBJECTIVE

To evaluate a technique of autologous internal limiting membrane (ILM) fragment transplantation for the treatment of large, chronic, and/or refractory macular holes (MH).

DESIGN

This was a 6-month prospective interventional case series.

METHOD

Ten eyes of 10 patients with MH underwent pars plana vitretomy (PPV) and ILM peeling followed by transplantation of an autologous ILM fragment to the MH. Six patients had primary MH with an internal diameter greater than 500 µm and a duration of more than 18 months, including 1 patient with nonproliferative diabetic retinopathy previously treated with panretinal photocoagulation. Four eyes with MH had previously been submitted to PPV (i.e. 1 for retinal detachment and 3 to attempt to close large MH). One of the latter also displayed juxtapapillary choroidal neovascularization due to age-related macular degeneration. The primary and secondary outcomes were MH closure and improvement of the best corrected visual acuity (BCVA), respectively.

RESULTS

Complete MH closure was achieved in all cases. A statistically significant improvement in the average BCVA was observed after 6 months of follow-up (p = 0.018; paired t test). The BCVA improved in 8 eyes (80%), and in 6 of those eyes it improved by ≥ 15 letters. In 1 patient, the BCVA remained unchanged after the surgery, but the visual field reportedly improved. One patient experienced a slight worsening (0.16 logMAR). Two cases developed atrophy of the retinal pigment epithelium despite MH closure and BCVA improvement.

CONCLUSION

Treatment with autologous ILM fragment transplantation seems to be an efficient alternative for large, chronic, and refractory MH.

20 g PPV with indocyanine green-assisted ILM peeling versus 23 g PPV with brilliant blue G-assisted ILM peeling for epiretinal membrane

To compare the anatomical and visual outcomes of 20 gauge (g) pars plana vitrectomy (PPV) with indocyanine green (ICG)-assisted internal limiting membrane (ILM) peeling and 23 g PPV with brilliant blue G (BBG)-assisted ILM peeling for idiopathic epiretinal membrane (ERM). 38 eyes of 38 patients with idiopathic ERM were included. They were divided in two groups: group 1 (18 eyes) underwent 20 g PPV with ICG-assisted ILM peeling and group 2 (20 eyes) 23 g PPV with BBG-assisted ILM peeling. Postoperative best-corrected visual acuity (BCVA) and central macular thickness (CMT) were compared. Average BCVA in group 1 improved significantly from 0.60 logarithm of the minimal angle of resolution (log MAR) at baseline to 0.3 log MAR postoperatively. Average BCVA in group 2 improved significantly from 0.60 log MAR at baseline to 0.3 log MAR postoperatively. Mean CMT reduced significantly from 473 to 375 μm in group 1 and from 486 to 396 μm in group 2. There were no significant differences in the BCVA and CMT between the groups. Both surgical methods appeared to be safe and provided similar anatomical and visual outcomes.

Effect of distance and duration of illumination on retinal ganglion cells exposed to varying concentrations of brilliant blue green

Background

The objective of the study was to determine the safety parameters of using brilliant blue green (BBG) for chromovitrectomy by assessing the cytotoxicity of BBG on cultured retinal ganglion cells (RGCs) exposed to illumination.

Methods

RGCs were exposed to two concentrations of BBG (0.25 and 0.5 mg/mL) under metal halide illumination at varying distances (1 and 2.5 cm), intensities (990 and 2,000 Fc), and durations (1, 5 and 15 minutes). Cell viability was assessed using the WST-1 and CellTiter 96^® AQueous One solution cell proliferation assays.

Results

Using the WST-1 assay, with high-intensity illumination, viability of RGCs ranged from 97.5±16.4% of controls with minimum BBG and light exposure (0.25 mg/mL BBG and illuminated for 1 minute at 2.5 cm distance) to 53.1±11.3% of controls with maximum BBG and light exposure (0.50 mg/mL and illuminated for 15 minutes at 1 cm distance; P < 0.01). With medium-intensity illumination, RGCs showed better viability, ranging from 95.1±7.2% of controls with minimum BBG and light exposure to 72.3±12.8% of controls with maximum BBG and light exposure. CellTiter 96^® AQueous One assay showed similar results.

Conclusion

RGCs seem to safely tolerate up to 5 minutes of exposure to 0.5 mg/mL BBG under diffuse medium-intensity illumination (990 Fc).

Dye solutions based on lutein and zeaxanthin: in vitro and in vivo analysis of ocular toxicity profiles

PURPOSE

To study the safety profile of Lutein/Zeaxanthin(L/Z)-based natural dye solutions in in vitro and in vivo models.

MATERIAL AND METHODS

In vitro cytotoxicity and cellular growth experiments were carried out on ARPE-19 and human corneal epithelial (HCE) cell lines using different L/Z-based dye solutions, either alone or in association with brilliant blue (BB) or trypan blue (TB). Light and transmission electron microscopy studies were performed seven days after intravitreal injection of dye solutions in rabbits. Electroretinogram (ERG) recordings were taken at baseline and before histopathology.

RESULTS

In vitro cytotoxicity assays demonstrated that the different L/Z-based solutions (from 0.3 to 2%), either alone or in association with BB (0.025%) or TB (0.04%), did not significantly alter mitochondrial activity (≤15%) in the cell lines tested. In addition, in vitro cell growth was inhibited by up to 60% depending on the dye solution, and in direct proportion to the concentration assayed. There was no evidence of structural alterations in the neurosensory retina, retinal pigment epithelium (RPE), or choriocapillaris-choroidal complex. b-Wave ERG records showed no significant differences (±15.2%) in comparison with baseline.

CONCLUSIONS

L/Z-based dye solutions demonstrated a safe profile in in vitro and in vivo models, and may be a useful tool for staining intraocular structures.

Evaluation of macular retinal ganglion cell-inner plexiform layer thickness after vitrectomy with internal limiting membrane peeling for idiopathic macular holes

PURPOSE

To evaluate macular retinal ganglion cell-inner plexiform layer (GCIPL) thickness changes after Brilliant Blue G-assisted internal limiting membrane peeling for idiopathic macular hole repair using a high-resolution spectral-domain optical coherence tomography (SD-OCT).

METHODS

32 eyes from 32 patients with idiopathic macular holes who underwent vitrectomy with internal limiting membrane peeling between January 2011 and July 2012 were retrospectively analyzed. GCIPL thickness was measured before surgery, and at one month and at six months after surgery. Values obtained from automated and semimanual SD-OCT segmentation analysis were compared (Cirrus HD-OCT, Carl Zeiss Meditec, Dublin, CA).

RESULTS

No significant differences were found between average GCIPL thickness values between preoperative and postoperative analysis. However, statistical significant differences were found in GCIPL thickness at the temporal macular quadrants at six months after surgery. Quality measurement analysis performed by automated segmentation revealed a significant number of segmentation errors. Semimanual segmentation slightly improved the quality of the results.

CONCLUSION

SD-OCT analysis of GCIPL thickness found a significant reduction at the temporal macular quadrants at 6 months after Brilliant Blue G-assisted internal limiting membrane peeling for idiopathic macular hole.

Lutein and zeaxanthin toxicity with and without brilliant blue in rabbits

PURPOSE

To evaluate the safety profile of solutions containing lutein and zeaxanthin alone or associated with brilliant blue (BB).

METHODS

Twenty-eight New Zealand rabbits were used to evaluate 4 concentrations of the various dye solutions: 0.5% lutein/zeaxanthin; 0.5% lutein/zeaxanthin associated with 0.0125% BB; 0.3% lutein/zeaxanthin associated with 0.025% BB; and 0.25% lutein/zeaxanthin associated with 0.05% BB. The pHs of the dye solutions ranged from 6.5 to 7.2 and the osmolarities from 280 to 320 mOsm/mL. Each rabbit had 0.1 mL of one of the dyeing solutions injected into the vitreous cavity of the right eye, while balanced salt solution (BSS) was injected into the left eye as the control. Scotopic electroretinography responses were recorded in all eyes at different time points. The animals were sacrificed at 1 and 7 days after injection; the eyes were analyzed by light and transmission electron microscopy.

RESULTS

No significant (P>0.05) differences were seen in the a- and b-wave amplitudes among groups at any given point in time. Light and electron microscopy findings showed no significant abnormalities either, and were similar to the histological findings after intravitreal BSS injection.

CONCLUSIONS

Lutein and zeaxanthin alone or in association with BB showed a good safety profile in this experimental model.

Indocyanine green concentrations used in chromovitrectomy cause a reversible functional alteration in the outer blood-retinal barrier

PURPOSE

To assess tight junction integrity in cultured human foetal retinal pigment epithelium (RPE) after exposure to clinically relevant indocyanine green (ICG) concentrations.

METHODS

Human foetal RPE was cultured with the Hu & Bok method. The apical compartments of well-differentiated cultures were exposed to 0.125, 0.05 and 0.025 mg/ml ICG with or without 10-min illumination. Vehicle and trypsin/EDTA or EDTA alone served as controls. Three minutes was chosen to mimic surgical exposure time, while 3 h was used for toxicity assays, with subsequent wash out. Cell-cell junctions were studied before and after exposure by phase contrast microscopy and immunofluorescence (ZO-1). Blood-retinal barrier function was measured through transepithelial electrical resistance (TER).

RESULTS

At 6-8 weeks postconfluence, RPE had grown into pigmented hexagonal monolayers with stable TER (435-1227 Ω*cm(2) ). After 3 min ICG exposure, cell morphology remained unchanged, with patchy cell-cell dissociation in positive controls. A continuous ZO-1 signal was detected in ICG groups, whereas trypsin controls showed patchy loss of the tight junction stain. TER had dropped at 1.5 h after 3 min exposure to 22.8 ± 3.1%, compared with 10.2 ± 3.9% in positive controls. Surgical light illumination did not affect TER. After 3 h exposure to 0.05 mg/ml ICG, TER decreased to 58.1 ± 8.3%, while vehicle controls maintained similar levels as prior to exposure (92.7 ± 2.4%). TER recovered in all ICG groups to prior levels within 3 days.

CONCLUSION

Indocyanine green (ICG) exposure induced a transient decrease in transepithelial electrical resistance, despite unaltered tight junction structure.

Chromovitrectomy: update

The basic concept for the application of vital dyes during vitreoretinal surgery is to assist in highlighting preretinal membranes and tissues which are very thin and semitransparent and thus difficult to detect. The vital dyes may be classified according to different criteria, where the most commonly applied includes chemical classification. In ophthalmic surgery, vital dyes are widely used in cataract and vitreoretinal surgery. The vital dyes, indocyanine green, infracyanine green, and brilliant blue stain the internal limiting membrane, and trypan blue and triamcinolone acetonide help to visualize epiretinal membranes and vitreous, respectively. This review exhibits the current literature regarding the properties of vital dyes, techniques of application, indications, and toxicities during vitreoretinal surgery and, also suggests that the field of chromovitrectomy represents an expanding area of research.

Effect of novel vital dyes on outer blood-retina barrier function in cultured human retinal pigment epithelium

PURPOSE

To assess tight junction (TJ) integrity in cultured human fetal retinal pigment epithelium (HFRPE) after exposure to clinically relevant novel vital dyes.

METHODS

HFRPE floater cells were harvested from RPE primary cultures of 4 donor eyes and seeded on polyester Transwell® for 4-6 weeks. The apical compartments of well-differentiated cultures were exposed to 0.005 mg/ml Coomassie violet R200 (CVR), methyl 2B (M2B) or Orange II. Periods of 30-300 s were chosen to mimic surgical exposure times, while 3 h was used for toxicity assays, with subsequent washout. Cell-cell junctions were studied by immunofluorescence (zonula occludens-1, ZO-1). Transepithelial electrical resistance (TER) was measured regarding blood-retina barrier (BRB) function.

RESULTS

At 4-6 weeks after confluence, HFRPE had grown into pigmented hexagonal monolayers with stable TER values (451-1,520 Ω·cm(2)). After 300-second dye treatments, a continuous ZO-1 signal was detected in all vital dye-treated groups 1.5 h after exposure, whereas trypsin controls showed patchy loss of the TJ stain. TER of CVR-, M2B- and Orange-II-treated groups had dropped 1.5 h after exposure to 148 ± 58.4, 162 ± 23.7 and 164 ± 18.5 Ω·cm(2), respectively, compared to 73 ± 44.9 Ω·cm(2) in positive controls. After 3 h of exposure to 0.005 mg/ml vital dyes in thick drops, TER maintained similar levels to those prior to exposure (90.8 ± 4.7% of the original values, 93.8 ± 6.5 and 91.9 ± 3.6%, respectively), together with no difference from the vehicle controls (94.8 ± 6.6%). TER values recovered in all groups to prior levels within 3 days.

CONCLUSION

Novel vital dyes (CVR, M2B and Orange II) caused no outer BRB function alteration.

Dyes for Eyes™: hydrodynamics, biocompatibility and efficacy of 'heavy' (dual) dyes for chromovitrectomy

As epiretinal membranes (ERMs), the internal limiting membrane (ILM) and the vitreous cortex are essentially transparent tissues, or translucent structures, nontraumatic removal may be challenging in various types of macular surgery. Vital dyes stain these thin tissues, thus allowing for better visualization of these structures during vitrectomy and selective 'membrane peeling' from the underlying retina. To avoid swirling of the dye within the fluid-filled vitreous cavity, and to better target the dye onto the macula, a fluid-air exchange is commonly performed. However, this may jeopardize visualization of the macula during peeling due to clouding of the posterior lens capsule, and may lead to postoperative visual field defects. Recently, a new dye solution for staining the ERM and ILM simultaneously has been developed that circumvents the need for fluid-air exchange, i.e. MembraneBlue-Dual™. This paper will focus on the hydrodynamics and biocompatibility of this 'heavy' dual dye and its efficacy for staining of the ILM and/or ERMs during posterior segment surgery in a multicenter clinical setting.

Contrast recognizability during brilliant blue G - and heavier-than-water brilliant blue G-assisted chromovitrectomy: a quantitative analysis

PURPOSE

To evaluate the potential of heavier-than-water brilliant blue G (BBG-D(2) 0) to stain the internal limiting membrane (ILM) during chromovitrectomy.

METHODS

In a nonrandomized, prospective, clinical multicentre study, 71 consecutive chromovitrectomy interventions in 71 patients were analysed. During routine 23-gauge vitrectomy, conventional 0.25 mg/ml BBG was employed in 21 and 0.25 mg/ml BBG-D(2) 0 in 50 patients. All interventions were videotaped. Post-operatively, video frames were viewed and dye performance assessed subjectively and objectively. Main outcome measure was the chromaticity difference between the stained ILM and the unstained underlying retina, measured by means of an objective and quantitative analysis method to describe colour contrast strengths as they are perceived by the human eye.

RESULTS

Removal of the ILM was possible in all interventions without additional vital dyes. BBG-D(2) 0 readily sank to the retinal surface, while conventional BBG tended to swirl up throughout the vitreous cavity. Conventional BBG was removed either with active suction or with a flute needle. Brilliant blue G-D(2) 0 needed to be whirled up from the retinal surface with a flute needle before aspiration. Objective chromaticity measurements yielded a mean chromaticity score of 7.98 for BBG-D(2) 0 and 6.51 for BBG (p = 0.09).

CONCLUSIONS

Brilliant blue G-D(2) 0 readily sinks to the retinal surface after injection and can be conveniently removed with a flute needle or active suction during chromovitrectomy. Based on the premises of the chromaticity measurements in this study, BBG's ILM staining capacity was not significantly improved through the recent revision its preparation, although a tendency towards slightly improved contrasts between the ILM and the underlying retina was observed.

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.

Investigating the biocompatibility of two new heavy intraocular dyes for vitreoretinal surgery with an isolated perfused vertebrate retina organ culture model and a retinal ganglion cell line

BACKGROUND

During vitreoretinal surgery, vital dyes are used to visualize anatomical structures. Substances with a density higher than water are added to facilitate sedimentation and staining. BBG with 4% PEG (ILM Blue) and BBG with TB and 4% PEG (MBB Dual) are two new dyes. This study evaluates biocompatibility of the new dye solutions, using cell cultures and electrophysiological evaluation.

METHODS

To determine cytotoxicity of ILM Blue and MBB Dual for 30, 60, 120 and 320 seconds, monolayer cultures of retinal ganglion cells (RGC5) were used. For functionality testing, bovine retinas were isolated and superfused with an oxygen-saturated nutrient solution, and the electroretinogram (ERG) was recorded. The two dye solutions were applied epiretinally for 30, 60 and 120 seconds. ERG recovery was monitored.

RESULTS

After staining with ILM Blue, no statistical significant reduction of a- or b-wave amplitudes at the end of the wash-out was recorded. For MBB Dual, only a significant reduction of the a-wave amplitudes after 30 seconds of application at the end of the wash-out was noticed, while no statistically different changes for a- and b-wave amplitudes up to 120 seconds were noted. During the MTT assay, we noted no significant difference in cell viability after 30, 60, 120 and 320 seconds of staining with ILM blue, MBB Dual or 4% PEG in comparison to the control group (DMEM, Triton X-100 0.9% as positive control) after formazan extraction.

CONCLUSIONS

ILM Blue and MBB Dual seem to be safe for clinical use for a staining period of up to 120 seconds, probably even up to 320 seconds.

Comparative in vitro safety analysis of dyes for chromovitrectomy: indocyanine green, brilliant blue green, bromophenol blue, and infracyanine green

PURPOSE

Vital dyes such as infracyanine green (IfCG), brilliant blue green (BBG), and bromophenol blue (BPB) have been used as an alternative to indocyanine green (ICG) during chromovitrectomy. We compared the in vitro toxicity of IfCG, BBG, and BPB with ICG on the retinal pigment epithelial cells and retinal ganglion cells at various concentrations to optimize the safe dose and duration of exposure.

METHODS

Cultured retinal ganglion cells (RGC-5) and human retinal pigment epithelial cells (ARPE-19) were exposed to 2 concentrations (0.25 and 0.5 mg/mL) of ICG, IfCG, BBG, and BPB at various time intervals (1, 5, 15, and 30 minutes). Cell viability was quantified with neutral red assay, and mode of cell death was evaluated with flow cytometry-based Annexin V and propidium iodide staining.

RESULTS

Exposure to ICG resulted in 48%-74% reduction in neutral red uptake in both RGC-5 and ARPE-19 cells, after an exposure time of ≥5 minutes compared with control (P < 0.001). Infracyanine green, BBG, and BPB were significantly less toxic on the 2 cell lines at exposure times <15 minutes. (Reduction in cell viability ranged from 6.9% ± 3.3% to 29.3% ± 7.4% when compared with control, P > 0.5.) However, among the newer dyes, BBG caused necrosis in retinal pigment epithelial cells and retinal ganglion cells as the exposure time period increased beyond 5 minutes.

CONCLUSION

Newer vital dyes, IfCG, BBG, and BPB, are significantly less toxic on retinal ganglion cells and retinal pigment epithelial cells' cell lines when compared with ICG. Infracyanine green was least toxic among the three newer dyes studied.

Ultrastructure of the membrana limitans interna after dye-assisted membrane peeling

The purpose of this study was to investigate the ultrastructure of the membrana limitans interna (internal limiting membrane, ILM) and to evaluate alterations to the retinal cell layers after membrane peeling with vital dyes. Twenty-five patients (25 eyes) who underwent macular hole surgery were included, whereby 12 indocyanine green (ICG)- and 13 brilliant blue G (BBG)-stained ILM were analyzed using light, transmission electron and scanning electron microscopy. Retinal cell fragments on the ILM were identified in both groups using immunohistochemistry. Comparing ICG- and BBG-stained membranes, larger cellular fragments were observed at a higher frequency in the BBG group. Thereby, the findings indicate that ICG permits an enhanced separation of the ILM from the underlying retina with less mechanical destruction. A possible explanation might be seen in the known photosensitivity of ICG, which induces a stiffening and shrinkage of the ILM but also generates retinal toxic metabolites.

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.