EFFECTS OF INTRAVITREAL INDOCYANINE GREEN INJECTION IN RABBITS

Internal limiting membrane peeling in macular hole surgery

Since the era when macular hole was considered untreatable, macular hole surgery has come a long way to being one of the most successful surgeries. Internal limiting membrane (ILM) peeling has been an essential step of macular hole surgery since the establishment of the role of ILM in the aetiopathogenesis and progression of macular hole. However, the novel technique was not all virtuous. It had some vices which were not evident immediately. With the advent of spectral domain optical coherence tomography, short- and long-term effects of ILM peeling on macular structures were known; and with microperimetry, its effect on the function of macula could be evaluated. The technique has evolved with time from total peeling to inverted flap to just temporal peeling and temporal flap in an attempt to mitigate its adverse effects and to improve its surgical outcome. ILM abrasion technique and Ocriplasmin may eliminate the need of ILM peeling in selected cases, but they have their own limitations. We here discuss the role of ILM in the pathogenesis of macular hole, the benefits and adverse effects of ILM peeling, and the various modifications of the procedure, to then explore the alternatives.

Customized Color Settings of Digitally Assisted Vitreoretinal Surgery to Enable Use of Lower Dye Concentrations During Macular Surgery

Purpose

This study evaluated the color contrast ratio (CCR) of the internal limiting membrane (ILM) using different color settings of digitally assisted vitreoretinal surgery (DAVS) with different indocyanine green (ICG) concentrations.s

Methods

This is a prospective comparative observational study. Consecutive patients that underwent 25G vitrectomy and ILM peeling using a standard operating microscope (SOM) (25 eyes), DAVS Ver. 1.1 (12 eyes), or DAVS Ver. 1.3 (13 eyes) were enrolled. The SOM and DAVS Ver. 1.1 groups used 0.075% ICG, and the DAVS Ver. 1.3 group used 0.025% ICG. In DAVS Ver. 1.1, macular CCR was compared between four different presets in the red, green, and blue channels: Default (Red (R) 100%, Green (G) 100%, and Blue (B) 100%); Preset 1 (R 20%, G 100%, B 100%); Preset 2 (R 80%, G 80%, B 100%), and Preset 3 (R 85%, G 100%, B 90%). In DAVS Ver. 1.3, macular CCR was evaluated using two different customized settings that modified the hue and saturation: Customized Setting 1 (R 86, G 100, B 100%, Hue +2°, Saturation 90%, Gamma 1.2) and Customized Setting 2 (R 90, G 100, B 100%, Hue +20°, Saturation 100%, Gamma 0.9). All patients underwent ophthalmologic examinations including BCVA at baseline and at 12 months.

Results

In DAVS Ver. 1.1, macular CCR was highest in Preset 3 (P < 0.01). The CCR of Customized Setting 2 of DAVS Ver. 1.3 using 0.025% ICG did not differ from that of Preset 3 in DAVS Ver. 1.1 using 0.075% ICG. Furthermore, there was no significant difference in BCVA between the Customized Setting 2 of DAVS Ver. 1.3 with 0.025% ICG and the Preset 3 of DAVS Ver. 1.1 with 0.075% ICG groups at baseline and at 12 months (P > 0.05, respectively).

Conclusion

Customized DAVS settings enabled surgeons to use a 3-fold lower ICG concentration in ILM peeling.

Outer Plexiform Layer Angle: A Prognostic Factor for Idiopathic Macular Pucker Surgery

Purpose. To investigate the efficacy of idiopathic macular pucker (epimacular membrane) surgery and to identify the possible prognostic factor. Methods. This was a retrospective study which enrolled 38 patients with idiopathic macular pucker who underwent 23-gauge pars plana vitrectomy (PPV) with indocyanine green-assisted peeling of epiretinal membrane (ERM) and internal limiting membrane (ILM). Visual outcomes were assessed at the baseline and during the follow-up including best-corrected visual acuity (BCVA) and metamorphopsia score, as well as outer plexiform layer (OPL) angle and central retinal thickness (CRT) using spectral-domain optical coherence tomography (SD-OCT). A comparison was made between patients with the prepeeling CRTs ≥500 μm and those <500 μm. A comparison was also made between patients with the prepeeling OPL angles ≥130° and those <130°. Based on the prepeeling parameters, the correlations between various prepeeling and postpeeling visual functions were analyzed. Results. Mean follow-up was 36.07 ± 4.62 months (range 1.30–96.70 months). BCVA was significantly improved from 0.26 ± 0.03 to 0.67 ± 0.04 $\left(p<0.001\right)$ ; metamorphopsia score was significantly reduced from 1.42 ± 0.16 to 0.61 ± 0.08 $\left(p<0.001\right)$ ; CRT was significantly decreased from 519.62 ± 13.41 μm to 385.37 ± 8.97 μm $\left(p<0.001\right)$ . Greater prepeeling OPL angle (≥130°) was associated with significantly greater BCVA improvement (Snellen E/LogMAR: $p=0.01/0.03$ ) and greater metamorphopsia reduction $\left(p=0.03\right)$ , as compared to smaller OPL angle (<130°) with less BCVA improvement and less metamorphopsia reduction. However, the final BCVA improvement and metamorphopsia reduction relevant to the prepeeling smaller CRT (<500 μm) did not significantly differ from that relevant to the prepeeling greater CRT (≥500 μm; $p>0.05$ ). Endophthalmitis, retinal tear, or retinal detachment was not observed after peeling. Conclusion. Indocyanine green-assisted ERM/ILM peeling combined with small gauge vitrectomy is associated with significant visual acuity improvement and metamorphopsia reduction in patients with idiopathic macular pucker. Greater prepeeling OPL angle rather than CRT might act as a useful prognostic factor in predicting better final visual functional outcomes.

[Effect of Dyes Containing Lutein on Enhanced Visibility of Epiretinal Pathologies in Intraoperative OCT]

BACKGROUND

Epiretinal membranes are a disorder leading to metamorphopsia and loss in visual function. The gold standard in therapy is vitrectomy with membrane peeling, usually performed with chromovitrectomy. The aim of this study was to examine whether dyes containing lutein are capable of enhancing visualization of epiretinal tissue in intraoperative optical coherence tomography (iOCT).

PATIENTS AND METHODS

This was a prospective study that included 20 eyes of 20 patients with idiopathic epiretinal membranes scheduled for surgery. 23 G pars plana vitrectomy with intraoperative assistance of iOCT was performed in all cases. Staining of epiretinal membranes was performed with dyes containing trypan blue, brilliant blue G and lutein (tripledyne and dualdyne, both Kemin Industries Inc., USA).

RESULTS

In all patients (n = 20), staining of epiretinal tissue was good, and crystalline lutein particles could be well depicted in iOCT compared to soluble lutein that does not enhance visualisation of epiretinal tissue in iOCT.

CONCLUSIONS

The addition of lutein to commonly used dye formulations offers good staining properties and, in case of crystalline lutein, also enhances epiretinal tissue in iOCT.

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.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

ARMANDODASILVA, FIALHO SILVIALIGORIO, LIBER ANDREMAURICIO, YOUNG LUCYHWAYUE, VENTURA DORAFIX. Intravitreal injection of polysorbate 80: a functional and morphological study

ABSTRACT Objective : to determine the functional and morphological effects at rabbits retina of PS80 concentration used in the preparation of intravitreal drugs. Methods: eleven New Zealand rabbits received a intravitreal injection of 0.1ml of PS80. As control, the contralateral eye of each rabbit received the same volume of saline. Electroretinography was performed according to a modified protocol, as well as biomicroscopy and retina mapping before injection and seven and ten days after. Animals were euthanized in the 30th day and the retinas were analyzed by light microscopy. Results: eyes injected with PS80 did not present clinical signs of intraocular inflammation. Electroretinography did not show any alteration of extent and implicit time of a and b waves at scotopic and photopic conditions. There were no morphological alterations of retinas at light microscopy. Conclusion: intravitreal injection of PS80 in the used concentration for intravitreal drug preparations do not cause any functional or morphological alterations of rabbit retinas. These results suggest that PS80 is not toxic to rabbit retinas and may be safely used in the preparation of new lipophilic drugs for intravitreal injection.

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.

Ocular Biocompatibility of Poly-N-Isopropylacrylamide (pNIPAM)

Purpose. To study the safety of intravitreal injections of poly-N-isopropylacrylamide (pNIPAM) tissue adhesive in rabbit eyes. Methods. Twelve study rabbits received an intravitreal injection of 0.1 mL 50% pNIPAM in the right eye. Follow-up examinations included color fundus photography, fundus fluorescein angiography (FA), optical coherence tomography (OCT), and electroretinography (ERG). Subsequent to the last follow-up assessment, the rabbits were sacrificed and histopathological study on the scleral incision sites was performed. Results. All study animals developed mild to moderate levels of inflammatory reaction in the conjunctiva, anterior chamber, and the anterior vitreous during the first month of follow-up. After this period, the level of the inflammatory reaction progressively decreased and completely disappeared after the third month of follow-up. The lens and cornea remained clear during the entire follow-up period. OCT and FA did not show areas of retinal damage or neovascularization. Histological and ERG studies of eyes injected with pNIPAM demonstrated absence of retinal toxicity. Conclusion. Intravitreal injections of pNIPAM were nontoxic in this animal study, and pNIPAM may be safe to be used as a bioadhesive in certain retinal diseases.

Poly-N-isopropylacrylamide (pNIPAM): a reversible bioadhesive for sclerotomy closure

PURPOSE

To determine the safety and efficacy of poly-N-isopropylacrylamide, a thermoresponsive adhesive, for sutureless sclerotomy closure in rabbits.

METHODS

Eight rabbits were randomized into three groups: short-term acute, mid-term chronic, and long-term chronic studies. A corresponding control group in which the scleral wounds were sutured by 6-0 vicryl sutures was assigned for each study group. A 20-gauge sclerotomy was performed following a core vitrectomy and 0.1 mL of 50 % liquid poly-N-isopropylacrylamide was applied to the scleral wounds. Before the polymer application, the scleral surface was raised above 32 °C using a halogen bulb lamp. Follow-up exams included color external and fundus photography, fundus fluorescein angiography, optical coherence tomography, and electroretinography. After the last follow-up assessment, the rabbits were sacrificed and histopathological studies on the scleral incision sites were performed.

RESULTS

Scleral wound healing was observed in the long-term chronic study rabbits. Histological studies were able to identify poly-N-isopropylacrylamide polymer at the sclerotomy site in the mid-term chronic study rabbits. Besides iatrogenic cataracts due to mechanical instrument touch in 2 rabbits, no other ocular abnormalities were identified in any of the eyes in the perioperative setting or during the follow-up period. Cornea, retina, and vitreous remained unaffected, and no abnormal inflammatory reaction or endophthalmitis was noticed in the 3 study groups. Filtering blebs indicative of leakage through the sclerotomies were not observed during the follow-up period.

CONCLUSION

Poly-N-isopropylacrylamide may provide effective in vitro scleral adhesion above 32 °C. Clinical studies are required to evaluate its utility in patients undergoing pars plana vitrectomy.

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: a new dye for chromovitrectomy

PURPOSE

To evaluate the feasibility, advantages, and safety of a novel lutein-based dye for improving identification and removal of the vitreous, internal limiting membrane, and epiretinal membrane during chromovitrectomy in humans.

METHODS

We prospectively evaluated 12 eyes that underwent pars plana vitrectomy using the dye in patients with macular hole, epiretinal membrane, or proliferative diabetic retinopathy/tractional diabetic macular edema. One surgeon performed standard chromovitrectomy and completed a postoperative questionnaire to compare the staining with that of the available dyes. The peeled membranes were evaluated histologically. Follow-up examinations were performed on postoperative Days 1, 7, 30, 90 and 180; best-corrected visual acuity, optical coherence tomography, fluorescein angiography, autofluorescence, and visual fields were performed.

RESULTS

The green dye was deposited on the posterior pole because of its higher density than balanced saline solution; vigorous dye flushing into the vitreous cavity was unnecessary. The dye stained the posterior hyaloid/vitreous base by deposition onto the vitreous; brilliant blue stained the internal limiting membrane. The epiretinal membrane was poorly stained. The best-corrected visual acuity improved in all eyes without clinical toxicity or toxicity on images/visual fields. Histology showed effective removal of the internal limiting membrane and epiretinal membrane in all eyes.

CONCLUSION

The new dye improved intraoperative identification of the internal limiting membrane and the posterior hyaloid/vitreous base during chromovitrectomy.

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.

Soluble lutein in combination with brilliant blue as a new dye for chromovitrectomy

A new dye for vitreoretinal surgery comprised of soluble lutein/zeaxanthin 1 % and brilliant blue 0.025 % is advantageous compared with other dyes currently used for chromovitrectomy, and showed no signs of toxicity at 1 month of follow-up.

PURPOSE

To evaluate the feasibility and safety of a dye [soluble lutein/zeaxanthin (LZ) 1 % and brilliant blue (BB) 0.025 %] for improving removal of vitreous, epiretinal membranes (ERM), and internal limiting membranes (ILM) in humans.

METHODS

We prospectively evaluated 18 eyes treated surgically for a macular hole or ERM. Eighteen surgeons performed chromovitrectomy using the dye, and completed a questionnaire to evaluate the efficacy and safety of the dye. . Examinations included best-corrected visual acuity and intraocular pressure measurements and optical coherence tomography, fluorescein angiography, and autofluorescence performed at baseline and days 1, 7, and 30 postoperatively.

RESULTS

The green dye was deposited on the posterior pole; vigorous dye flushing into the vitreous cavity was unnecessary. All surgeons reported that the ILM stained greenish-blue; 94.4 % reported ILM peeling adequate; the ERM stained poorly. No evidence of toxicity was observed.

CONCLUSION

The new dye deposited on the posterior pole due to its higher density. The ability to stain the ILM was similar to BB. The new dye has ability to stain the vitreous, hyaloid, and especially the ILM satisfactorily. The new dye may be useful during chromovitrectomy.

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.

Staining properties of brilliant blue depending on different incubation times and solvents in humans

PURPOSE

Intravitreous injection of vital dyes, e.g. brilliant blue (BBG), promotes better visualization of the internal limiting membrane (ILM). This paper investigates the staining properties of BBG depending on different incubation times and 2 types of solvents--5% glucose (GL) or saline solution--in a prospective study in patients.

METHODS

This paper investigates various aspects of BBG in various methods. An interventional prospective study was conducted in patients to examine the binding properties of the blue dye diluted in either saline or 5% GL to epiretinal membranes (ERMs) and ILMs. Forty-nine consecutive patients older than 18 years scheduled for macular ERM, vitreomacular traction and macular hole surgeries were prospectively recruited. The primary outcomes of this study were the degree of ILM and ERM staining. The secondary outcomes of the study were the need of reinjection of BBG or any other dye, the ability of BBG to stain the vitreous, and frequency of complications. The staining of the ILM and ERM were graded as no staining, little, moderate or strong staining.

RESULTS

There was no correlation between age (p = 0.32) or gender (p = 0.33) in the staining affinity of BBG to either the ILM or ERM. BBG may be an appropriate staining agent for the ILM in the majority (82%) of surgeries; however, in approximately half of the cases (45%) surgeons considered BBG not enough for ERM coloring and visualization. There is a tendency of BBG to stain the ILM better when saline solution is used compared to GL 5%; however, this was not statistically significant (p = 0.64). There was no difference in the staining efficacy of BBG to the ERMs by either solution (p = 0.70), despite the low staining affinity.

CONCLUSION

BBG became the state-of-the-art dye for ILM identification. Differences in staining properties may imply that BBG should not be considered as first-line stain for ERM surgery. BBG is effective in ILM staining in over 80% of macular hole surgeries.

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.

Monitoring the effect of mild ischemia with a built-in light-emitting diode contact lens electrode and a low-cost custom-made apparatus

Electroretinography (ERG) is widely used in clinical work and research to assess the retinal function. We evaluated an easy to build ERG setup adapted for small animals comprising two contact lens electrodes with a built-in light-emitting diode and a custom-made amplification system. The system's sensitivity was tested by monitoring ERG in albino rat eyes subjected to mild ischemia. Flash ERG was recorded by two contact lens electrodes positioned on the rat's corneas and used alternately as test or reference. The a- and b-wave amplitudes, a-wave latency, b-wave implicit time and oscillatory potentials (OPs) were analyzed. Ischemia was achieved by elevating the intraocular pressure in the eye's anterior chamber. ERG was recorded on post-ischemia (PI) days -1, 1, 3 and 7. Morphological changes were analyzed on hematoxylin/eosin stained 5 µm sections of control 7d PI retinas. In control eyes, ERG exhibited a pattern similar to a standard recording. Retinas subjected to mild ischemia preserved ordered layered morphology, exhibiting approximately 30% loss of ganglion cells and no changes in gross morphology. By day 3 PI, ischemia caused an increase in the a-wave amplitude (from 34.9 ± 2.7 to 45.4 ± 4.3 µV), a decrease in the b-wave amplitude (from 248 ± 13 to 162 ± 8 µV), an increase in a-wave latency (from 11.1 ± 0.3 to 17.3 ± 1.4 ms) and b-wave implicit time (from 81.0 ± 1.6 to 90.0 ± 2.5 ms), and attenuation of OPs. The described setup proved sensitive and reliable for evaluating subtle changes in the retinal function in small animals.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Non-Foveal Macular Holes After PPV for Macular Pucker

Purpose:

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

Materials and Methods:

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

Results:

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

Conclusion:

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

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.

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.

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

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Morphologic and clinical effects of subretinal injection of indocyanine green and infracyanine green in rabbits

PURPOSE

The aim of this study was to determine the effects of subretinal injection of indocyanine green (ICG), infracyanine (IfCG), and balanced salt solution (BSS) in rabbits.

METHODS

Ten (10) animals were subjected to a subretinal injection of 0.05% ICG (279 mOsm), 0.5% IfCG (276 mOsm), and BSS (300 mOsm) used as a control. Animals were examined at 6, 12, and 24 h and 14 days following the surgical procedure by indirect binocular ophthalmoscopy, fluorescein angiography (FA), and light and transmission electron microscopy.

RESULTS

The subretinal injection of ICG caused damage to all retinal layers and retinal pigment epithelium (RPE) during the entire follow-up. Subretinal injection of IfCG resulted in abnormalities of the photoreceptor outer segments (POSs) during the entire follow-up; however, abnormalities of the photoreceptor inner segments (PISs) and outer nuclear layer (ONL) were observed only 24 h and 14 days after surgery; no RPE damage was observed. FA showed that window defects were more prominent in the subretinal ICG bleb position than the IfCG-related area. BSS caused only abnormalities of the POS layer and no RPE alterations.

CONCLUSIONS

Subretinal injection of 0.05% ICG results in more significant retinal damage than 0.5% IfCG. In this model, iodine-free IfCG demonstrates a safer profile than a tenfold lower concentration of ICG, which contains iodine in its composition.

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

PURPOSE

Indocyanine green (ICG) dye was shown to improve the visualization of preretinal tissues during chromovitrectomy. However, controversy arose regarding the safety of intravitreal ICG application, because worse functional outcomes and a higher incidence of retinal pigment epithelium (RPE) changes and visual field defects were reported. The mechanisms of ICG-related toxicity and their relevance for chromovitrectomy are reviewed.

METHODS

A literature search was performed from 1998 through 2005 for relevant information related to the mechanisms of intravitreal ICG toxicity. Animal and clinical data on intravitreal ICG-related toxicity were collected to clarify the mechanisms of the risk of intravitreal ICG injection.

RESULTS

Over 80 controversial in vitro, ex vivo, and in vivo animal investigations as well as clinical reports on intravitreal ICG staining were found in the literature. The main postulated mechanisms of intravitreal ICG-related toxicity were as follows: biochemical direct injury to the ganglion cells/neuroretinal cells, RPE cells, and superficial retinal vessels; apoptosis and gene expression alterations to either RPE cells or neuroretinal cells; osmolarity effect of ICG solution on the vitreoretinal interface; light-induced injury; and mechanical cleavage effect to the internal limiting membrane/inner retina. Whereas the exact mechanism of intravitreal ICG-related damage remains yet to be determined, most animal experiments proposed that ICG dye has a dose-dependent toxic effect on retinal tissue. This hypothesis was supported by clinical data, because better functional outcomes were obtained when low dye concentrations and short incubation times were reported.

CONCLUSIONS

Much evidence supports that ICG dye has a dose-dependent toxic effect on the retina. Therefore, the following recommendations to minimize toxic effects on the retina are proposed: dye injection in concentrations as low as possible; avoidance of repeated ICG injections onto bare retina; dye injection far from the macular hole to prevent direct dye contact with the RPE; short incubation time of ICG in the vitreous cavity to diminish the concentration in contact with the retinal tissue; and the light pipe kept far from the retina throughout the whole surgical procedure.

Changes in intraocular indocyanine green concentrations during macular hole surgery

PURPOSE

To report changes in intraocular indocyanine green (ICG) concentration which was used for visualization of the internal limiting membrane (ILM) during vitreous surgery on 3 eyes of 3 patients with full-thickness macular hole.

METHODS

During intraocular surgery with ICG-assisted ILM peeling, aliquots of intraocular fluid obtained at 1 min after ICG administration (0.5 ml of 5 mg/ml ICG solution), before and after ILM peeling, and before and after fluid/gas exchange were subjected to spectrophotometric analysis.

RESULTS

Intravitreous concentrations of ICG were dramatically reduced to approximately 0.4 microg/ml during the surgery for macular hole in all cases.

CONCLUSION

The present study indicates that the levels of remaining intraocular ICG concentrations after macular hole surgery are much lower than the levels that induced retinal toxicity in experimental models.

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

PURPOSE

To investigate the histologic and clinical effects of subretinal injection of patent blue (PB) and trypan blue (TB) in rabbits.

METHODS

Dutch-belted rabbits (n=8) were vitrectomized followed by subretinal injection of 2.4 mg/ml PB (285 mOsm) and 1.5 mg/ml TB (312 mOsm); balanced salt solution (BSS) (300 mOsm) served as the control. Animals were examined 6, 12, and 24 hr and 14 days after the procedure by fluorescein angiography (FA) and indirect ophthalmoscopy; for retinal toxicity, histologic evaluation studies were performed by light and transmission electron microscopy.

RESULTS

FA examination demonstrated window defects suggestive of retinal pigment epithelium (RPE) atrophy in positions of subretinal TB injection, but this was not observed after subretinal injection of PB or BSS. Histologic evaluation disclosed only minimal abnormalities on the photoreceptor outer segment (POS) after subretinal injection of BSS during all follow-up. Subretinal injection of PB caused POS and photoreceptor inner segment (PIS) abnormalities 12 and 24 hr after surgery as well as outer nuclear layer (ONL) damage 14 days after surgery. Subretinal TB injection resulted in POS and PIS damage at 12 hr follow-up. The ONL damage was observed 24 hr after surgery; additionally, POS, PIS, ONL, and RPE abnormalities were observed 14 days after surgery after TB injection.

CONCLUSIONS

Subretinal injection of TB induced more significant clinical and histologic damage of neurosensory retina/RPE than did PB or BSS. Future human studies are necessary to access the clinical relevance of these in vivo experiments.

Vital dyes for chromovitrectomy

PURPOSE OF REVIEW

The aim of this article is to present the current state-of-the-art in regard to the application of vital dyes during vitreoretinal surgery, 'chromovitrectomy', as well as to overview the current literature regarding the properties of dyes, techniques of application, indications, and complications in chromovitrectomy.

RECENT FINDINGS

A large body of published research has recently addressed the toxicity profile of indocyanine green for chromovitrectomy. Experimental data demonstrate dose-dependent toxicity of indocyanine green to various retinal cells. Newer generation vital dyes for chromovitrectomy include trypan blue, patent blue, triamcinolone acetonide, infracyanine green, sodium fluorescein, bromophenol blue, fluorometholone acetate and brilliant blue. Novel instruments may enable a selective painting of preretinal tissues during chromovitrectomy.

SUMMARY

This review suggests that the field of chromovitrectomy represents an expanding area of research. The first line agents for internal limiting membrane staining in chromovitrectomy are indocyanine green, infracyanine green, and brilliant blue. Patent blue, bromophenol blue and trypan blue arose as outstanding biostains for visualization of epiretinal membranes. Novel dyes available for chromovitrectomy deserve further investigation.

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

PURPOSE

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

DESIGN

Experimental study.

PARTICIPANTS

Twenty Dutch-belted rabbits.

METHODS

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

MAIN OUTCOME MEASURES

Clinical outcome, fluorescein angiography, and histopathologic results.

RESULTS

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

CONCLUSIONS

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

ECCENTRIC MACULAR HOLES AFTER VITRECTOMY WITH PEELING OF EPIMACULAR PROLIFERATION

PURPOSE

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

METHODS

In a retrospective review of 631 consecutive patients who underwent vitrectomy with peeling of the epimacular proliferation and in most cases the internal limiting membrane (ILM) from May 2001 to May 2005, 6 patients were found to have developed an eccentric macular hole postoperatively.

RESULTS

Eccentric macular holes developed 9 days to 8 months (mean, 3.1 months) after epimacular proliferation peeling. The ILM was peeled in addition to the epimacular proliferation in five of the six cases. Of the six eccentric macular holes, four were located temporal to the fovea, one was located superior to the fovea, and one was located nasal to the fovea. Final visual acuities after a mean follow-up period of 17.3 months were 20/20 in 2 eyes, 20/25 in 1 eye, 20/40 in 2 eyes, and 5/200 in 1 eye. The eye with the eccentric macular hole nasal to the fovea had the poorest final visual acuity of 5/200.

CONCLUSION

Eccentric macular hole occurring after vitrectomy to remove epimacular proliferation is an uncommon postoperative finding. To our knowledge, this is the largest case series of such patients reported. Various explanations have been suggested for the etiology of these holes, but there remains no consensus.

Evaluation of Indocyanine Green Toxicity to Rat Retinas

PURPOSE

To investigate the toxicity of indocyanine green (ICG) on retinal cells using cultured retinal pigment epithelium (RPE) cells and the effects of intravitreous injection of ICG into rat eyes.

METHODS

Cultured RPE cells were exposed to various concentrations of ICG for 2 min, a viability assay was performed 1 day after exposure. For an in vivo study, 5 microl of ICG (5 or 25 mg/ml) were injected into the vitreous cavity of rat eyes, which were examined 1, 3 and 7 days after the injection by histological and glutamine synthetase (GS) immunohistological evaluation.

RESULTS

Viabilities of RPE cells were decreased dependent on the ICG dose. In the histological evaluation, we observed differences of effects of ICG between the central retinal area and the peripheral area. ICG injection caused degeneration of all retinal layers in the central retinal area. GS immunoreactivities decreased by ICG injection, which corresponded to an area of severe destruction.

CONCLUSION

A high concentration of ICG may cause toxic effects on retinal cells. Mueller cell dysfunction may play some role in the retinal toxicity caused by ICG.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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