Different biocompatibility of crystalline triamcinolone deposits on retinal cells in vitro and in vivo

Vitreous Substitutes as Drug Release Systems

Vitreous substitutes are traditionally used to stabilize the retina after vitrectomy. In recent years, various approaches have been developed for using the vitreous substitute not only as a tamponade but also as a drug release system to tackle ocular diseases. This review provides an overview of the requirements for vitreous substitutes and discusses the current clinically applied as well as novel polymer-based vitreous substitutes as drug delivery systems, including their release mechanisms, efficiencies, challenges, and future perspectives.

[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.

Intraoperative Optical Coherence Tomography-Guided Membrane Peeling for Surgery of Macular Pucker: Advantages and Limitations

PURPOSE

Epiretinal membranes (ERMs) are a disorder leading to progressive vision loss and metamorphopsia. The gold standard in therapy is vitrectomy with membrane peeling. The aim of this study was to assess whether the use of intraoperative optical coherence tomography (iOCT), which allows tomographic visualization of the membrane during peeling, enables peeling without staining.

METHODS

This prospective study included 30 eyes of 30 patients with idiopathic ERMs scheduled for surgery. Pars plana vitrectomy with iOCT was performed in all cases, whereas staining of ERMs was only performed if needed. Internal limiting membrane (ILM) peeling was performed in case of wrinkled retinal surface after peeling of ERMs.

RESULTS

In 63% (n = 19) eyes the ERM could be peeled successfully without use of staining. Nevertheless, in 89% (n = 17) of patients having had ERM peeling without dye, staining of the ILM was performed afterwards for peeling the ILM. Best corrected visual acuity improved in 80% (n = 24) and remained unchanged in 7% (n = 2) 3 months after surgery. There were no significant differences in postoperative results between patients with and without staining for ERM peeling.

CONCLUSIONS

Use of iOCT helps to complete ERM peeling in a majority of cases without use of a chromovitrectomy dye, but as iOCT fails to visualize the ILM, chromovitrectomy still facilitates macular surgery in a majority of cases.

A Review of the Role of Intravitreal Corticosteroids as an Adjuvant to Antibiotics in Infectious Endophthalmitis

Infectious endophthalmitis is an important cause of vision loss worldwide. This entity most often occurs as a complication of intraocular surgery especially following cataract surgery or intravitreal injection. Endophthalmitis is regarded as a serious complication following ocular surgery and the final visual outcome is fundamentally contingent on timely recognition and intervention. Intravitreal and oral antibiotics in combination with pars plana vitrectomy or vitreous aspiration remain the mainstay in the management of endophthalmitis. However, significant inflammation may persist even after sterilization of the intraocular cavities with appropriate antibiotics resulting in failure of treatment. This forms the basis for the use of intravitreal corticosteroids as an adjuvant to antibiotics in the management of infectious endophthalmitis. In the index manuscript, we review the existing literature to determine the role of intravitreal corticosteroids as an adjuvant to antibiotics in treating infectious endophthalmitis, and discuss their beneficial effects and controversial concerns.

Biocompatibility of the vital dye Acid Violet-17 on retinal pigment epithelial cells

Purpose

To examine the viability and differentiation of retinal pigment epithelial (RPE) cells after exposure to the vital dye Acid Violet-17 (AV-17).

Methods

Bovine RPE cells were incubated with AV-17 (0.0625–0.5 mg/mL) for 30 seconds or 5 minutes. Viability was determined by live/dead staining, cleaved CASP3 immunostainings, and MTT test. Actin cytoskeleton was visualized by Alexa 488-phalloidin. Immunocytochemistry was performed to determine the levels of ZO-1, CTNNB1, and KRT19.

Results

Exposure to AV-17 at the concentrations of 0.25–0.5 mg/mL resulted in a dose-dependent decrease in viability, the loss of ZO-1 from tight junctions, translocation of CTNNB1 into the cytoplasm and nucleus, disarrangement of the actin cytoskeleton, and a slight increase in KRT19.

Conclusion

AV-17 at a concentration <0.125 mg/mL is likely to be well tolerated by the RPE cells, whereas the concentrations from 0.25 mg/mL onward can reduce viability and induce dedifferentiation particularly after long-term exposure.

Management of pseudophakic cystoid macular edema

Pseudophakic cystoid macular edema (PCME) is a common complication following cataract surgery. Acute PCME may resolve spontaneously, but some patients will develop chronic macular edema that affects vision and is difficult to treat. This disease was described more than 50 years ago, and there are multiple options for clinical management. We discuss mechanisms, clinical efficacy, and adverse effects of these treatment modalities. Topical non-steroidal anti-inflammatory agents and corticosteroids are widely used and, when combined, may have a synergistic effect. Intravitreal corticosteroids and anti-vascular endothelial growth factor (anti-VEGF) agents have shown promise when topical medications either fail or have had limited effects. Randomized clinical studies evaluating anti-VEGF agents are needed to fully evaluate benefits and risks. When PCME is either refractory to medical therapy or is associated with significant vitreous involvement, pars plana vitrectomy has been shown to improve outcomes, though it is associated with additional risks.

Safety of intravitreal triamcinolone acetonide: an electrophysiologic and histopathological study in rabbits

AIM

To evaluate the retinal safety of various doses of intravitreal triamcinolone acetonide (TA) in rabbits.

METHODS

Thirty New Zealand albino rabbits were divided into five groups (six animals each). In group 1 (control group), each animal received a single intravitreal injection of 0.1mL phosphate buffered saline. In groups 2, 3, 4 and 5, each rabbit received a single intravitreal injection of 4, 8, 16 and 32mg of TA, respectively. Each dose was contained in 0.1mL phosphate buffered saline. Clinical ocular examinations were performed before the injection and on the 1st, 3rd, 10th and 17th post-injection days. A standard dark adapted electroretinogram (ERG) was obtained before injection and on the 3rd, 10th and 17th post-injection days. After 17d, animals were sacrificed and their eyes prepared for pathological examination.

RESULTS

By monitoring ERG as a functional index for the retina, intravitreal injection of 4mg TA showed no significant ERG changes. At doses of 8, 16 and 32, hyper-abnormal responses in a- and b- waves of ERG were detected on the 3rd post-injection day. These changes gradually returned back to normal limits after 17d. Histopathological examination of the retina of all animals showed no pathological changes.

CONCLUSION

High doses of intravitreal TA seemed to have enhancing effects on the retinal function with gradual return to normal limits with no pathological changes detected in examined eyes.

The retinal biocompatibility of dyes in the ex vivo model of the isolated superfused vertebrate retina

BACKGROUND

Peeling of the internal limiting membrane or epiretinal membranes is a successful principle in macular surgery to achieve a functional benefit. Different dyes are used to facilitate the identification of intraocular tissues. The aim of our work was to investigate the retinal tolerance to the different dyes and their solvent carriers to provide valuable data for surgeons in handling for an optimal intraoperative use.

METHODS

Using the ex vivo model of the isolated superfused vertebrate retina technique, the effects of the dyes were tested on human and bovine retinal function. The retinas were perfused with an oxygen preequilibrated standard solution. The electroretinogram (ERG) was recorded using Ag/AgCl electrodes. After recording stable ERG amplitudes, the dyes brilliant blue G, indocyanine green, trypan blue, patent blue, triamcinolone and their solvent carriers were investigated.

RESULTS

Reductions of the ERG amplitudes were found for each tested dye. The effects after application of the dyes were dependent on time and concentration of the applied dyes, which were different for each dye.

CONCLUSION

In part, the ERG has shown strong effects already after a short period of dye application. Surgeons who rely on the intraocular use of the dyes should keep in mind our findings, and the use of some dyes should be limited to selected cases. The well-considered use of the dyes by the surgeons could lead to a better functional outcome and avoid a possible harmful outcome of the surgery after mishandling.

Preservative-free triamcinolone acetonide injectable suspension versus "traditional" triamcinolone preparations: impact of aggregate size on retinal biocompatibility

PURPOSE

To evaluate the biocompatibility of the three currently most commonly used triamcinolone acetonide (TA) preparations on retinal cells.

METHODS

Preservative containing KL (Kenalog-40; Bristol-Myers Squibb, Princeton, NJ), compounded preservative-free triamcinolone acetonide (PFTA; compounded from Volon A; Dermapharm, Vienna, Austria), and preservative-free triamcinolone acetonide injectable suspension (TRIESENCE; Alcon, Inc, Fort Worth, TX) (0.01-1 mg/mL) were either added directly on top or separated by a Boyden chamber filter or by a layer of vitreous to confluent cell cultures of retinal pigment epithelial cells (ARPE19) or retinal ganglion cells (RGC5). The distribution pattern of the TA crystals was assessed microscopically. Cell viability was assessed using MTT-ELISA and Live/Dead-Assay.

RESULTS

Sedimentation of triamcinolone acetonide injectable suspension, KL, or PFTA caused a pronounced decrease in cell viability. Cytotoxicity was most pronounced when triamcinolone acetonide injectable suspension and PFTA were used. Without direct sedimentation of TA crystals on top of the cells, none of the three formulations were cytotoxic. Triamcinolone acetonide injectable suspension showed the largest and most dense TA crystal aggregates on top of the cells.

CONCLUSION

Retinal cytotoxicity of TA seems only to occur when there is intimate contact of TA crystals with the cellular membrane. Cytotoxicity depends on the number and size of TA crystal aggregates-with larger conglomerates being more harmful. Of the TA formulations tested, triamcinolone acetonide injectable suspension had the strongest tendency to form large TA crystal conglomerates and to gravitate downward.

Functional and structural effect of intravitreal indocyanine green, triamcinolone acetonide, trypan blue, and brilliant blue g on rat retina

PURPOSE

The purpose of this study was to evaluate the functional and structural damage of the retina after intravitreal injections of four different dyes in the rat.

METHODS

Rats were injected intravitreally with indocyanine green (ICG), trypan blue, triamcinolone acetonide, or brilliant blue G in the right eye. The other eye was injected with saline and served as a control. Simultaneous bilateral electroretinograms were recorded before injection and 7 and 28 days after injection. Histology and immunohistochemistry analyses with antibodies recognizing glial fibrillary acidic protein and protein kinase C were performed 28 days after the initial injection on both eyes.

RESULTS

Seven days after dye injection, the electroretinogram response of the treated eyes was altered in each group. At 1 month, eyes injected with triamcinolone acetonide, trypan blue, or brilliant blue G fully recovered, whereas eyes treated with ICG had A-wave and B-wave reduction of 65% and 63%, respectively. The inner nuclear layer thickness was statistically decreased in the ICG group (P = 0.003) but not with other dyes. Protein kinase C staining was decreased in the ICG group only, but no abnormal qualitative staining was found with either glial fibrillary acidic protein or protein kinase C antibodies with any dye.

CONCLUSION

Among the four tested dyes, only ICG led to functional and structural retinal damage.

The options to minimize the surgical trauma to treat ocular diabetic complications and to improve postoperative recovery and quality of life require an individualized approach

Within the past ten years, small incision pars-plana vitrectomy, and refined microsurgical techniques, together with the introduction of various intravitreally applied drugs, significantly improved the anatomical and functional outcome. Unfortunately many diabetic patients with vitreoretinal complications also have cataract. In diabetic retinopathy, the benefit of simultaneous cataract surgery was long under debate due to possible side effects such as fibrinous reaction or secondary glaucoma. We review recent reports about the results of PPV for complication of diabetic retinopathy and the influence of a simultaneous cataract surgery, that compare different surgical approaches. Pars plana vitrectomy carried out with conventional 0,9 mm incisions (20G PPV) were related to higher incidences of postoperative inflammatory reactions and to a higher frequency of postoperative hypertensive events as compared to small incision vitrectomy (23G PPV). Postoperative recovery was faster in eyes with 23G surgery than after 20G surgery, with no delay by a simultaneous cataract surgery. A 23G-PPV improves the postoperative recovery and the quality of life for the diabetic patient. Cataract is no longer an obstacle for a vitreoretinal surgery. Postoperative recovery is faster and the new technique has less side effects than the conventional technique. In the future, a drug assisted vitrectomy will further reduce the surgical trauma. However, the new options are not equally benefitial for all patients. A further improvement in the quality of life will require a more individualized approach of microsurgical treatment for ocular complications of diabetes.

The safety profile of alkylphosphocholines in the model of the isolated perfused vertebrate retina

BACKGROUND

Alkylphosphocholines (APCs) are synthetic phospholipid derivatives, and have been demonstrated to inhibit ocular cell proliferation in vitro and in vivo. Currently, they are applied clinically for their antitumoral and antiparasitic properties, but have not yet been implemented for clinical use in proliferative ophthalmic disorders. The purpose of this study was to assess the safety of APC in the ex vivo model of the isolated perfused vertebrate retina.

METHODS

Bovine retina preparations were perfused with an oxygen pre-equilibrated standard solution. The electroretinogram (ERG) was recorded using Ag/AgCl-electrodes. After recording stable b-wave amplitudes, an APC was applied at the following concentrations to the nutrient solution: 0.25 microM, 2.5 microM and 25 microM. To investigate the effects of APC on photoreceptor function, a test series at the same concentrations was performed to evaluate the effects of APC on the a-wave amplitude. Aspartate at a concentration of 1 mM was added to the nutrient solution to obtain stable a-wave amplitudes. Thereafter, APC was applied at the same concentrations to the nutrient solution. The recovery of the ERG amplitudes was followed up for 75 minutes.

RESULTS

No reduction of the a- and b-wave amplitude was found at the end of the exposure time with APC added in each test series. No differences were found between the ERG amplitudes before and after application of APC at the end of the washout.

CONCLUSIONS

In the ex vivo model of the isolated perfused vertebrate retina, APC has proved to be a safe compound in the concentrations applied. Thus, APCs should further be considered as promising candidates for future clinical applications in ophthalmology.

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.