Effects of subretinal injection of patent blue and trypan blue in rabbits

Anatomical and functional changes after internal limiting membrane peeling

Internal limiting membrane (ILM) peeling has been an acceptable step in vitrectomy surgeries for various retinal diseases such as macular hole, chronic macular edema following epiretinal membrane (ERM), and vitreoretinal traction. Despite all the benefits, this procedure has some side effects, which may lead to structural damage and functional vision loss. Light and dye toxicity may induce reversible and irreversible retina damage, which will be observed in postoperative optical coherence tomography scans. Retinal nerve fiber layer damage is attributed to ganglion cell degeneration and axonal transport alteration and dissociated optic nerve fiber layer is due to Müller cell damage. Eccentric MHs and recurrence of previous MHs may also lead to vision loss. Iatrogenic retinal damage may cause structural retinal changes without significant vision loss or progression to choroidal neovascularization. The mechanism of persistent macular edema after membrane peeling is still unclear, but it has been related to tractional trauma and blood-retina barrier damage. The reappearance of ERM is another cause of decreased vision after ILM peeling, which might be secondary to incomplete membrane removal. In glaucoma patients, ILM peeling is associated with significantly worsening the mean deviation on the visual field test after the surgery. We discussed various causes of vision loss and structural changes following ILM peeling. These causes may be attributed to the surgical procedure itself or the associated steps, instruments, and dyes used during the ILM peeling procedure.

Three-Year Safety Results of SAR422459 (EIAV-ABCA4) Gene Therapy in Patients With ABCA4-Associated Stargardt Disease: An Open-Label Dose-Escalation Phase I/IIa Clinical Trial, Cohorts 1-5

PURPOSE

To report on the safety of the first 5 cohorts of a gene therapy trial using recombinant equine infectious anemia virus expressing ABCA4 (EIAV-ABCA4) in adults with Stargardt dystrophy due to mutations in ABCA4.

DESIGN

Nonrandomized multicenter phase I/IIa clinical trial.

METHODS

Patients received a subretinal injection of EIAVABCA4 in the worse-seeing eye at 3 dose levels and were followed for 3 years after treatment.

MAIN OUTCOME MEASURES

The primary end point was ocular and systemic adverse events. The secondary end points were best-corrected visual acuity, static perimetry, kinetic perimetry, total field hill of vision, full field electroretinogram, multifocal ERG, color fundus photography, short-wavelength fundus autofluorescence, and spectral domain optical coherence tomography.

RESULTS

The subretinal injections were well tolerated by all 22 patients across 3 dose levels. There was 1 case of a treatment-related ophthalmic serious adverse event in the form of chronic ocular hypertension. The most common adverse events were associated with the surgical procedure. In 1 patient treated with the highest dose, there was a significant decline in the number of macular flecks as compared with the untreated eye. However, in 6 patients, hypoautofluorescent changes were worse in the treated eye than in the untreated eye. Of these, 1 patient had retinal pigment epithelium atrophy that was characteristic of tissue damage likely associated with bleb induction. No patients had any clinically significant changes in best-corrected visual acuity, static perimetry, kinetic perimetry, total field hill of vision, full field electroretinogram, or multifocal ERG attributable to the treatment.

CONCLUSIONS

Subretinal treatment with EIAV-ABCA4 was well tolerated with only 1 case of ocular hypertension. No clinically significant changes in visual function tests were found to be attributable to the treatment. However, 27% of treated eyes showed exacerbation of retinal pigment epithelium atrophy on fundus autofluorescence. There was a significant reduction in macular flecks in 1 treated eye from the highest dose cohort. Additional follow-up and continued investigation in more patients will be required to fully characterize the safety and efficacy of EIAV-ABCA4.

Role of Vital Dyes in Chromovitrectomy

ABSTRACT

Chromovitrectomy, the intraocular application of dyes to assist visualization of preretinal tissues during vitreoretinal surgery, was introduced to avoid ocular complications related to internal limiting membrane peeling, inadequate removal of the vitreous, and incomplete removal of epiretinal membranes. Since 2000, chromovitrectomy has become a popular approach among vitreoretinal specialists. The first vital dye used in chromovitrectomy, indocyanine green, facilitated identification of the fine and transparent internal limiting membrane. Following indocyanine green, trypan blue was introduced to identify epiretinal membranes, and triamcinolone acetonide stained the vitreous well. Recently, additional natural dyes such as lutein and anthocyanin from the açaí fruit have been proposed for intraocular application during vitrectomy. The main goal of this review was to study the role of vital stains in chromovitrectomy and report the latest findings in the literature.

Patent Blue V as an Alternative Stain for DMEK Grafts: Safety, Stain Retention, and Feasibility

PURPOSE

To determine whether Patent Blue V (PB) can be used as an alternative dye for staining Descemet membrane endothelial keratoplasty (DMEK) grafts.

METHODS

DMEK grafts from donor corneas were stained with 2.5% PB for 4 minutes (n = 2), 2.5% PB for 10 minutes (n = 2), or 0.06% trypan blue (TB) for 4 minutes (n = 1). The stain intensity of the grafts was compared initially and at different time points over a 15-minute period of balanced salt solution wash using a grading scale based on a serial dilution series of PB. Three additional grafts were stained with 2.5% PB for 10 minutes and used in mock surgeries to assess stain retention after injection and manipulation in a donor eye model for 25 minutes. To assess the safety of PB, DMEK grafts were prepared from 10 pairs of corneas where one cornea was stained with 0.06% TB for 4 minutes and the mate cornea was stained with 2.5% PB for 10 minutes. The grafts were preloaded and stored for 5 days in Optisol-GS at 2°C to 8°C, and endothelial cell loss was quantified using Calcein-AM staining and FIJI segmentation by 2 masked readers.

RESULTS

PB stain intensities were lighter than TB-stained grafts. Grafts stained with 2.5% PB for 10 minutes retained sufficient color for the 25-minute duration of mock surgery. The average endothelial cell loss for PB versus TB grafts was 21.6% ± 5.3% versus 20.2% ± 5.4% (P = 0.202) as determined by reader 1 and 23.6% ± 4.8% versus 21.2% ± 5.8% (P = 0.092) as determined by reader 2.

CONCLUSIONS

PB is a viable alternative dye in DMEK grafts for applications where TB may not be available or approved for use.

Vital Dyes in Vitreomacular Surgery

Vital dyes contain complex molecules with chromophores that stain living tissues and have greatly enhanced identification and removal of transparent vitreoretinal tissues during surgery. Several "chromovitrectomy" dyes are frequently used by vitreoretinal specialists, including indocyanine green, trypan blue, brilliant blue G, and triamcinolone acetonide; other dyes are also under investigation. Trypan Blue was approved by the U.S. Food and Drug Administration (FDA) for epiretinal membrane removal, and preservative-free triamcinolone acetonide was approved by the FDA for intraocular use. However, currently available chromovitrectomy dyes have their limitations, and of particular concern for some of them is the possibility for acute and chronic toxicity to the neurosensory retina and retinal pigmented epithelium. The potentially irreversible acute toxicity and other limitations, such as lack of long-term safety profiles, highlight the need for further advancements. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:788-798.].

Photochemical degradation of trypan blue

Purpose

To investigate the photochemical degradation of trypan blue (TB) and to identify decomposition products.

Methods

Defined solution samples of TB and a mixture with lutein/zeaxanthin were exposed to blue light. Thermal degradation processes were ruled out using controls not subjected to irradiation. All samples were analyzed using optical microscopy, UV/Vis spectroscopy, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and nuclear magnetic resonance (NMR) spectrometry. Degradation kinetics were determined based on changes in absorbance; intermediates were identified by analyzing mass differences of characteristic fragment ion peaks within the fragmentation patterns, and assignments were verified by NMR.

Results

TB demonstrated a photochemical degradation, which can be triggered by lutein/zeaxanthin. Intermediates vary depending on the presence of lutein/zeaxanthin. The self-sensitized photodegradation of TB occurs under generation of dimethyl sulfate and presumed formation of phenol. In contrast, within the presence of lutein/zeaxanthin the decomposition of TB indicates the formation of methoxyamine and sulfonyl arin. Thermal degradation processes were not observed.

Conclusions

TB demonstrated a photodegradation that may be triggered by lutein/zeaxanthin and results in the formation of cytotoxic decomposition products. Our findings contribute to understand degradation mechanisms of TB and may elucidate previous clinical and experimental observations of cellular toxicity after TB application.

Modified technique of internal limiting membrane staining in idiopathic macular hole surgery

PURPOSE

To describe a new method of ILM staining with TB under perfluorocarbon in cases of full thickness idiopathic macular hole using the inverted ILM flap technique.

METHODS

This study was a prospective interventional case series that included 42 eyes of 42 patients who had full thickness idiopathic macular hole with a minimum diameter more than 400 µm. Patients consecutively underwent vitrectomy with inverted ILM flap technique using the modified ILM staining method.

RESULTS

Anatomic success was achieved in 40 patients (95.2%). The other two patients had flat-open macular holes with bare RPE (foveal defect of neurosensory retina). Among the 40 eyes with closed holes, 25 eyes were of the U-type closure (normal foveal contour) and 15 eyes were of the V-type closure (steep foveal contour). These 40 eyes remained closed during the 6 months follow-up period.

CONCLUSION

The modified technique of ILM staining using TB under PFCL is safe and effective in cases of idiopathic macular hole combined with the inverted ILM flap technique.

Clinically undetected retinal breaks causing retinal detachment: A review of options for management

The successful detection of retinal breaks is a critical step in rhegmatogenous retinal detachment surgery in order to prevent persistent/recurrent retinal detachments. Not all retinal breaks causing retinal detachments are obvious. Retinal breaks may be obscured by opacities that are either anterior segment related, lens related, or posterior segment related. Rules to identify breaks based on subretinal fluid configuration are more difficult to apply in pseudophakic, aphakic, and scleral buckle encircled eyes-and in eyes with repeat detachments and those with proliferative vitreoretinopathy. Exudative detachments exhibit characteristic features and must be ruled out. A thorough clinical examination preoperatively is important even if a vitrectomy is planned. We review the incidence and causes of undetected breaks, along with preoperative/clinical issues that may hinder break detection. We review the literature with respect to investigative approaches and techniques that are available to the vitreoretinal surgeon when primary breaks remain clinically undetected during the preoperative examination. We broadly divide the surgical approaches into ones where the surgeon utilizes techniques to pursue actively a search for breaks versus adopting a purely speculative approach. Advantages and disadvantages of various techniques are appraised. Intuitively one might argue that an encircling scleral buckle combined with vitrectomy would give higher single operation success than pars plana vitrectomy alone because "undetected" retinal breaks would be addressed by a 360° plombage. We could not confirm this concept. Newer techniques, such as pars plana vitrectomy augmented with dye extrusion or endoscopic-assisted pars plana vitrectomy, show encouraging results. Technological advances such as intraoperative optical coherence tomography will also help to broaden the vitreoretinal surgeon's armamentarium. At this time, there is no gold standard in terms of the recommended approach, and this is reflected in the many options that are available for management. The surgeon must consider the benefits versus the risk of their preferred approach.

Impact of Vital Dyes on Cell Viability and Transduction Efficiency of AAV Vectors Used in Retinal Gene Therapy Surgery: An In Vitro and In Vivo Analysis

Purpose

Treatment of inherited retinal degenerations using adeno-associated viral (AAV) vectors involves delivery by subretinal injection. In the latter stages, alteration of normal anatomy may cause difficulty in visualizing the retinotomy, retinal detachment extension, and vector diffusion. Vital dyes may be useful surgical adjuncts, but their safety and impact on AAV transduction are largely unknown.

Methods

The effects of Sodium Fluorescein (SF), Membrane Blue (MB), and Membrane Blue Dual (DB) at a range of dilutions were assessed on human embryonic kidney cells in vitro using an AAV2-green fluorescent protein (GFP) reporter at different multiplicities of infection. Flow cytometry analysis was performed to assess both cell viability and transduction efficiency. The effect on quantitative (q)PCR titer was determined. Balanced salt solution (BSS) or dilute DB (1:5 in BSS) were delivered subretinally into left/right eyes of C57BL/6J mice (n = 12). Retinal structure and function were analyzed by optical coherence tomography, autofluorescence, dark-and light-adapted full-field electroretinography.

Results

DB and MB were not toxic at any concentration tested, SF only when undiluted. The presence of dyes did not adversely affect the genomic titer. DB even increased the values, due to presence of surfactant in the formulation. AAV2-GFP transduction efficiency was not reduced by the dyes. No structural and functional toxic effects were observed following subretinal delivery of DB.

Conclusions

Only undiluted SF affected cell viability. No effects on qPCR titer and transduction efficiency were observed. DB does not appear toxic when delivered subretinally and improves titer accuracy. DB may therefore be a safe and helpful adjunct during gene therapy surgery.

Translational Relevance

This paper might be of interest to the retinal gene therapy community: it is a “bench to bedside” research paper about the potential use of dyes as a surgical adjunct during the gene therapy surgery. We have tested the potential toxicity and impact on transduction efficiency in an in vitro and in vivo model.

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.

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 vital dyes on retinal pigmented epithelial cell viability and apoptosis: implications for chromovitrectomy

PURPOSE

To investigate the in vitro effect of vital dyes on toxicity and apoptosis in a human retinal pigment epithelial cell line.

METHODS

ARPE-19 cells were exposed to brilliant blue (BBG), Evans Blue (EB), bromophenol blue (BroB), indocyanine green (ICG), infracyanine green (IfCG), light green (LG), fast green (FG), indigo carmine (IC) and Congo red (CR). Balanced salt solution was used as the control. Five different concentrations and 2 exposure times were tested. Cell viability was determined by the MTS (1-solution methyl thiazolyl tetrazolium) assay and apoptosis by Bax expression on Western blot.

RESULTS

All dyes significantly reduced cell viability after 3 min of exposure at all concentrations (p < 0.01), except for BBG that was safe at concentrations up to 0.25 mg/ml and CR up to 0.05 mg/ml, while LG was safe at all concentrations. Toxicity was higher after 30 min of exposure. Expression of Bax was upregulated after all dye exposures, except BBG; ICG had the highest Bax expression (p < 0.01).

CONCLUSIONS

Overall the safest dye was BBG followed by LG, IfCG, FG, CR, IC, BroB, EB and ICG. ICG was toxic at all concentrations and exposure times tested. Moreover, BBG was the only dye that did not induce apoptosis in ARPE-19 cells.

Retinal pigmented epithelial cells cytotoxicity and apoptosis through activation of the mitochondrial intrinsic pathway: role of indocyanine green, brilliant blue and implications for chromovitrectomy

Purpose

To investigate the in vitro effect of four vital dyes on toxicity and apoptosis in a human retinal pigment epithelial (RPE) cell line.

Methods

ARPE-19 cells were exposed to brilliant blue (BriB), methyl blue (MetB), acid violet (AcV) and indocyanine green (ICG). Balanced salt solution was used as control. Five different concentrations of each dye (1, 0.5, 0.25, 0.05 and 0.005 mg/mL) and two exposure times (3 and 30 min) were tested. Cell viability was determined by cell count and MTS assay and cell toxicity by LDH assay. Real-time PCR and Western blotting were used to access the apoptosis process.

Results

ICG significantly reduced cell viability after 3 minutes of exposure at all concentrations (p<0.01). BriB was safe at concentrations up to 0.25 mg/mL and MetB at concentrations up to 0.5 mg/mL, while AcV was safe up to 0.05 mg/ml, after 3 minutes of exposure. Toxicity was higher, when the cells were treated for 30 minutes. Expression of Bax, cytochrome c and caspase-9 was upregulated at the mRNA and protein level after ICG exposure, while Bcl-2 was downregulated. AcV and MetB were similar to control. However, BriB resulted in upregulation of Bcl-2, an antiapoptotic protein.

Conclusions

The safest dye used on RPE cells was MetB followed by BriB and AcV. ICG was toxic at all concentrations and exposure times tested. Moreover, ICG was the only dye that induced apoptosis in ARPE-19 cells. BriB significantly increased Bcl-2 protein levels, which might protect against the apoptosis process.

Anatomical and functional outcome in brilliant blue G assisted chromovitrectomy

PURPOSE

To evaluate the potential of brilliant blue G (BBG) for intraoperative staining of the inner limiting membrane (ILM) with respect to staining properties and surgical outcome.

METHODS

In a retrospective, non-comparative clinical case series, we analysed 17 consecutive chromovitrectomy interventions for surgery of macular holes, ERMs, vitreoretinal traction syndromes and cystoid macular oedema. Following complete posterior vitreous detachment, BBG was injected into the vitreous cavity at a concentration of 0.25 mg/ml, followed by immediate washout. Main outcome measures were staining properties, visual acuity, central visual field testing and optical coherence tomography (OCT) measurements over a mean follow-up period of 3 months.

RESULTS

ILM staining was somewhat less intensive for BBG than for average indocyanine green (ICG) chromovitrectomy. However, the ILM was removed successfully without additional ICG in 15/17 patients. Postoperative visual acuity was improved in 16/17 patients and remained unchanged in one patient. Central retinal OCT thickness showed a postoperative reduction, with values ranging from +7 to -295 microm (median -89 microm). Neither visual field defects nor any other adverse events were recorded.

CONCLUSION

BBG permits sufficient staining for safe ILM removal. In this short-term study, good anatomical and functional results were achieved and no adverse events were observed.

Retinal nerve fiber layer thickness evaluation after trypan blue-assisted macular surgery

PURPOSE

The purpose of this study was to evaluate retinal nerve fiber layer (RNFL) thickness changes in eyes undergoing trypan blue-assisted macular surgery using optical coherence tomography-3. This is a prospective noncomparative, interventional, and observational case series of 35 eyes of 35 consecutive patients (15 eyes with macular hole, 14 eyes with idiopathic macular pucker, and 6 eyes with tractional diabetic macular edema) who underwent pars plana vitrectomy and peeling of the epiretinal membrane and/or internal limiting membrane assisted with 0.1 mL of 0.15% trypan blue.

METHODS

The quantitative analysis of the peripapillary RNFL by optical coherence tomography was performed before surgery and 6 months postoperatively in both eyes of the same patient. The main outcome measures were significant changes in RNFL thickness (overall and by quadrant).

RESULTS

Optical coherence tomography assessment of the macular status at 6 months postoperatively showed closure of all macular holes and improvement in foveal contour in all cases of macular pucker or most cases of diabetic macular edema. Dissociated RNFL at the area of internal limiting membrane removal was observed in 9 eyes. No statistical significant changes in the mean RNFL thickness overall or by quadrant were observed after surgery.

CONCLUSION

Trypan blue-assisted peeling of macular epiretinal membranes and/or internal limiting membrane does not induce significant changes in RNFL thickness as measured by optical coherence tomography-3. Internal limiting membrane peeling may induce visible changes of the inner retinal surface possibly because of microdefects on macular nerve fiber layers.

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.

Dyes in ocular surgery: principles for use in chromovitrectomy

PURPOSE

To present the current state-of-the-art information regarding the properties, indications, surgical techniques, and toxic effects of current and past applications of vital dyes in chromovitrectomy.

DESIGN

Critical analysis and surgical perspective of the literature and recent studies.

METHODS

Review, interpretation, and commentary regarding the most relevant experimental as well as clinical studies including the authors' clinical and laboratory research.

RESULTS

There is a consensus that the application of vital dyes facilitates the delicate removal of intraocular membranes during vitreoretinal surgery. Controversy still remains around various issues, mainly potential toxicity and safety. There is room for further investigation of novel and specific vital dyes. Dyes such as Evans blue and light green may stain the internal limiting membrane very well, whereas fast green and indigo carmine may be very safe to the retina. However, comparing the staining and toxicity data has revealed that Bromophenol blue and Brilliant blue may be even better novel agents. The dyes currently used for different steps in chromovitrectomy are: triamcinolone acetonide for vitreous identification; indocyanine green, infracyanine green, and Brilliant blue for internal limiting membrane identification; and Trypan blue for epiretinal membrane identification.

CONCLUSIONS

Clear-cut safety profiles for the different dyes in chromovitrectomy have not yet been established, and current state-of-the-art staining-assisted procedures should be performed using concentrations and volumes as low as possible.