PRECLINICAL INVESTIGATION OF THE RETINAL BIOCOMPATIBILITY OF SIX NOVEL VITAL DYES FOR CHROMOVITRECTOMY

Presumed phototoxicity from macular vital staining with Brilliant Blue G and Trypan Blue: A post-market surveillance study, systematic review, and synthesis of the literature

Vital dyes are used to help visualize the retinal surface during macular surgery; however, they have been associated with phototoxicity. We synthesize and collate post-market surveillance data in two of the most commonly used dyes, Brilliant Blue G and Trypan Blue. We identified 69 cases, 59 of which were from the literature and 10 from manufacturer post-market surveillance. Of 69 vitrectomies, 39 were for macular hole, 24 for epiretinal membrane, 2 for vitreomacular traction, and 4 were not specified. The incidence of dye-mediated phototoxicity is likely rare, but is not possible to quantify, due to potential reporting and publication bias favouring dissemination of unusual safety events, but conversely underreporting is possible. Additionally, phototoxicity was reported prior to the introduction of vital stains, so it can be difficult to establish whether vital staining was contributory. Prolonged surgery and repeat staining were identified as risk factors. Characteristic clinical features were macular pigmentary change with hypo- and hyper-autofluoresence, often sparing the fovea. Final visual acuity tended to be worse than preoperatively, with some cases reduced to counting fingers. A reporting template is provided to encourage complete and standardised toxicity reporting and help build a robust evidence base.

Macular toxicity of vital dye after pars plana vitrectomy for idiopathic epiretinal membrane: A case report

Purpose

To describe the first reported case of outer retinal damage following the use of Membrane Blue Dual for epiretinal membrane (ERM) surgery.

Observations

A 74-year-old female underwent pars plana vitrectomy and ERM peeling assisted with Membrane Blue Dual for an idiopathic ERM. Postoperatively, the patient reported a decline in visual acuity with a central scotoma. Fundus examination revealed a well-defined retinal whitening in the peeling area which evolved into pigmentary changes as confirmed by fundus autofluorescence. Optical coherence tomography (OCT) showed loss of outer retinal layers and irregular mottling of the retinal pigment epithelium. Fundus and OCT appearance remained unchanged after 4 months and the central scotoma also persisted.

Conclusions and Importance

ERM surgery assisted with Membrane Blue Dual can induce major changes in retinal pigment epithelium and outer retinal layers. This adverse event which probably results from combined light and dye toxicity should be considered by all surgeons even though its occurrence is rare.

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.

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.].

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.

Investigation of new dyes for chromovitrectomy: preclinical biocompatibility of trisodium, orangell and methyl violet

Purpose

To investigate the retinal toxicity by electroretinography (ERG), clinical examination and histology after intravitreal injection of biological stains in two concentrations: Trisodium (0.50 g/L and 1.00 g/L), Orangell (0.25 g/L and 1.00 g/L) and Methyl Violet (0.50 g/L and 1.00 g/L).

Methods

Eighteen New-Zealand albinos rabbits were assigned in six groups (n = 3 in each group). The animals in group 1 received Trisodium in the dose of 0.50 g/L and group 2 received 1.00 g/L; Group 3 received Orangell in the dose of 0.25 g/L and group 4 received 1.00 g/L; Group 5 received Methyl Violet in the dose of 1.00 g/L and group 6 received 0.50 g/L. A volume of 0.05 mL of dye was injected in the right eyes, whereas the left eyes received the same volume of balanced salt solution (BSS) as control. ERG recordings and clinical examination were performed at baseline and seven days after intravitreal injection. The ERG responses at one week after injection were compared with baseline levels. A decrease in the post-injection amplitude of more than 50% was considered remarkable. After the 7-day follow-up, rabbits were euthanized and eye enucleated for light microscopy (LM) histological evaluation.

Results

At clinical examination by indirect ophthalmoscopy seven days after dye injection, all eyes were negative for cataract, hemorrhage, retinal detachment, and intraocular opacities. Amplitude analysis of maximum scotopic b-wave showed no significant reduction in either dye injected or control eyes. Neither dye nor BSS caused significant retinal alteration on LM at doses tested.

Conclusions

Trisodium, Orangell and Methyl Violet can be applied in future studies in order to prove the capacity to stain preretinal tissues and vitreous without toxicity. The three dyes did not induce significant ERG amplitude reduction or LM alterations in this preliminary experimental research. Trisodium, Orangell and Methyl Violet may be potentially useful vital dyes for ocular surgery, and deserve further investigation.

In vivo biocompatibility of a new cyanine dye for ILM peeling

PURPOSE

To investigate the biocompatibility of the new cyanine dye: 3,3'-Di-(4-sulfobutyl)-1,1,1',1'-tetramethyl-di-1H-benz[e]indocarbocyanine (DSS) as a vital dye for intraocular application in an in vivo rat model and to evaluate the effects of this dye on retinal structure and function.

METHODS

DSS at a concentration of 0.5% was applied via intravitreal injections to adult Brown Norway rats with BSS serving as a control. Retinal toxicity was assessed 7 days later by means of retinal ganglion cell (RGC) counts, light microscopy, optical coherence tomography (OCT), and electroretinography (ERG).

RESULTS

No significant decrease in RGC numbers was observed. No structural changes of the central retina were observed either in vivo (OCT) or under light microscopy. ERGs detected a temporary reduction of retinal function 7 days after injection; this was no longer evident 14 days after injection.

CONCLUSIONS

DSS showed good biocompatibility in a well-established experimental in vivo setting and may be usable for intraocular surgery as an alternative to other cyanine dyes. In contrast to indocyanine green, it additionally offers fluorescence in the visual spectrum. Further studies with other animal models are needed before translation into clinical application.

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.

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.

Chromovitrectomy and the vitreoretinal interface

It still remains unclear to which extent the presence and the amount of retinal debris seen in internal limiting membrane (ILM) specimens harvested during macular surgery for macular holes or epiretinal membranes are related to the procedure of ILM peeling itself or to modifications of the surgical technique, such as application of vital dyes for visualization of the ILM, or to pathological conditions with epiretinal membrane formation at the vitreoretinal interface. The presence of cellular fragments on the retinal side of the removed ILM appears to be of multifactorial origin, and additional causes besides dye application need to be considered. However, morphological studies with evaluation of vital dyes are still of relevance and provide additional insights into the ultrastructure of the vitreoretinal interface and its interaction with adjuvants used during macular surgery. Chromovitrectomy is an emerging field in vitreoretinal surgery. It is of importance to better understand the tissue-dye interactions, which not only alter the mechanical properties of the tissue being stained, but may also have an impact on the functional result postoperatively.

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.

Vital dyes increase the rigidity of the internal limiting membrane

PURPOSE

To assess the stiffness of the natural human internal limiting membrane (ILM) and evaluate potential changes of the mechanical properties following staining with brilliant blue (BB) and indocyanine green (ICG).

METHODS

Unstained ILM specimens were obtained during ophthalmic surgical procedures. After removal, the specimens were dissected into five parts. Two fragments were stained with BB and ICG, respectively, for 1 min, another two specimens were stained similarly followed by additional subsequent illumination using a standard light source (PENTA LUX x 50, Ophthalmologische Systeme GmbH Fritz Ruck). The fifth part served as an untreated control. All specimens were then analyzed using atomic force microscopy (AFM) in contact mode with a scan rate of 0.6 Hz. Two scan regions of 10 × 10 μm were chosen and stiffness was determined by using AFM in a force spectroscopy mode. The force curves were plotted with a data rate of 5000 Hz. In all specimens both the retinal side and vitreal side were analyzed.

RESULTS

Staining resulted in a significant increase in tissue stiffness. An increase was seen both for the vitreal (BB: P<0.001; ICG: P<0.01) and retinal side (BB: P<0.01; ICG: P<0.01), with the retinal side being significantly stiffer in all control and stained samples. Additional illumination after staining did further increase tissue rigidity in most samples but not significantly.

CONCLUSIONS

Staining significantly increases the stiffness of the human ILM. This might explain the fact that the stained ILM can be removed more easily and in larger fragments during vitreoretinal surgical procedures compared with unstained ILM.

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.

Use of lutein and zeaxanthin alone or combined with Brilliant Blue to identify intraocular structures intraoperatively

PURPOSE

To determine whether a natural dye solution based on lutein and zeaxanthin alone or combined with Brilliant Blue stains and facilitates peeling of intraocular membranes in human eyes.

METHODS

In this study of 60 cadaveric eyes, open-sky vitrectomy including posterior hyaloid detachment was performed. Different lutein and zeaxanthin concentrations (0.01-20%) were tested alone or combined with different Brilliant Blue concentrations (0.0125-0.025%) in the corneal endothelium, corneal epithelium, anterior and posterior capsule, vitreous cavity through the macula including the posterior hyaloid, and internal limiting membrane. The various dye solutions were in contact with the intraocular membranes for <1 minute and then were removed by mechanical aspiration or membrane peeling initiated and completed with intraocular forceps. The specimens were examined by light and electron transmission microscopy.

RESULTS

Contact between lutein and zeaxanthin and the retinal, lens, and vitreous surface resulted in orange and greenish staining of the intraocular membranes, which facilitated surgical steps in all eyes. Lutein and zeaxanthin alone was useful for vitreous identification and lutein and zeaxanthin combined with Brilliant Blue had strong affinity for internal limiting membrane and anterior capsule. Light microscopy confirmed internal limiting membrane removal in all eyes tested. No dye solutions remained in the eyes after the membrane removal.

CONCLUSION

A natural dye solution based on lutein and zeaxanthin alone or combined with Brilliant Blue efficiently stained the anterior capsule, vitreous, and internal limiting membrane in human cadaveric eyes and may be a useful tool for vitreoretinal or cataract surgery.

In vivo, in vitro toxicity and in vitro angiogenic inhibition of sunitinib malate

PURPOSE

To evaluate the in vivo and in vitro toxicity of sunitinib malate, a multikinase inhibitor molecule.

DESIGN

Experimental, Prospective, Controlled.

METHODS

Human retinal pigment epithelial (ARPE-19) and human umbilical vein endothelialcells (HUVECS) were used in a culture toxicity test and exposed to different concentrations of sunitinib malate for 18 hours. The HUVECs also were cultured to evaluate the angiogenesis inhibitory effect of sunitinib malate. Fundus photography and angiographic, electrophysiologic, and histopathologic evaluations with light and electron microscopy were performed in two groups of five rabbits each that received different intravitreal concentrations of the drug. Each rabbit received 0.1 ml of sunitinib malate in the right eye (one group with 12.5 mg/ml, the other group with 25 mg/ml); all animals received 0.1 ml of physiologic saline solution in the left eye. After sacrifice, the eyes were enucleated and fixed with modified Karnovsky solution.

RESULTS

No toxicity related to sunitinib malate was observed using an in vitro model with the 12.5 and 25 mg/ml solutions in HUVEC and ARPE cell cultures. No toxicity was observed in the in vivo model with 12.5 mg/ml, but light microscopy showed that the 25 mg/ml solution damaged the photoreceptors layer. No functional changes in the electroretinogram were observed in any group.

CONCLUSIONS

Sunitinib malate 12.5 mg/ml caused no toxicity in in vivo and in vitro models, but the 25 mg/ml concentration caused retinal changes suggesting toxicity in the in vivo model. Further research with the drug is needed in models of ocular neovascularization.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Ability of new vital dyes to stain intraocular membranes and tissues in ocular surgery

PURPOSE

To evaluate the ability of novel dyes to stain lens capsule (LC), internal limiting membrane (ILM), epiretinal membrane (ERM), and vitreous.

DESIGN

Experimental study in animal and human donor eyes.

METHODS

Thirteen dyes, methyl violet, crystal violet, eosin Y, sudan black B, methylene blue, toluidine blue, light green, indigo carmine, fast green, congo red, evans blue, brilliant blue, and bromophenol blue, were injected onto the LC and ILM of enucleated porcine eyes. The vitreous was stained with 2 mL of dyes for 1 minute. Six dyes (indigo carmine, evans blue, fast green, light green, bromophenol blue, and brilliant blue) were selected for experiments in human donor eyes and freshly removed ERM.

RESULTS

In the porcine eyes, ILM staining with methylene blue, toluidine blue, indigo carmine, evans blue, bromophenol blue, and fast green was moderate, and methyl violet, crystal violet, brilliant blue, or sudan black resulted in strong staining. Methyl violet, crystal violet, sudan black, toluidine blue, and methylene blue caused histologic damage in porcine retinas. Vitreous examination revealed moderate staining with congo red, crystal violet, fast green, eosin Y, methylene blue, toluidine blue, brilliant blue, bromophenol blue, and methyl violet and strong staining with light green and evans blue. ERMs showed strong staining with 0.5% evans blue and moderate staining with 0.5% light green, fast green, brilliant blue, and bromophenol blue. Evaluation of donor eyes disclosed moderate staining with evans blue, light green, and bromophenol blue and strong staining with 0.5% brilliant blue. Moderate or strong staining of the vitreous occurred with most dyes. LC evaluation showed moderate staining with 0.5% evans blue, fast green, and brilliant blue, whereas 0.5% light green produced strong LC staining.

CONCLUSIONS

Brilliant blue shows the best ILM staining, whereas bromophenol blue, evans blue, and light green also stain ILM. Most dyes bind well to LC, vitreous, and ERM.

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.

Visualizing vitreous in vitrectomy by triamcinolone

BACKGROUND

Visualizing vitreous and retinal surface during vitrectomy, choromovitrectomy, is a novel approach in vitrectomy.

METHODS

Triamcinolone acetonide (TA) is now most commonly used as an adjunct to vitrectomy for this purpose. Intraoperative use of TA can visualize posterior hyaloid, preretinal membrane, internal limiting membrane (ILM) during pars plana vitrectomy, and prolapsed vitreous during cataract surgery, which can make the procedure very safe and effective. TA-assisted vitrectomy is favorably applied to surgery for macular hole, proliferative vitreoretinopathy, diabetic retinopathy, uveitis, and others. In addition, this technique can disclose the residual hyaloid cortex pattern after surgical posterior vitreous detachment. Diffuse posterior hyaloids cortex is frequently seen in diabetic retinopathy and high myopia, and an island-like cortex is often left on the macula, which can be a scaffold of future macular pucker.

RESULTS

The prospective controlled clinical trial showed that TA-assisted vitrectomy reduced the incidence of intraoperative retinal break and retinal detachment more significantly than conventional vitrectomy, although post-operative visual acuity after 1 year was almost the same with each method. Adverse events related to TA-assisted vitrectomy included transient intraocular pressure elevation (approximately 5.0%); most of these events are manageable with topical treatment. The incidence of acute endophthalmitis was 0.03-0.05% , which was at a level comparable to conventional vitrectomy.

CONCLUSIONS

In this article, current status and the possible problems of TA-assisted vitrectomy are reviewed.