Evaluation of toxicity due to vital stains in isolated rat retinas

UVA-induced neurotoxicity in Japanese medaka (Oryzias latipes)

Ultraviolet radiation-induced neurodegeneration has been studied in the early stages of development in fish, but not extensively in the adult stage. The present study aimed at investigating the effects of ultraviolet radiation-A (UVA) in adult Japanese medaka (Oryzias latipes). The brain, spinal cord, and retina were examined histopathologically as nervous system target organs. Japanese medaka fish were exposed to 15, 30, and 60 min day^-1 UVA for 3 days, and samples were obtained 24 h and 14 days after UVA exposure. Neurohistopathological alterations in brain tissue included vacuoles, blood congestion, degeneration of neuropils, and pyknotic nuclei in neurons. Alterations in the spinal cord included neuronal cell degeneration, reduction in the spinal cord area, and degeneration of Mauthner cells. Retinal tissue showed vacuolation in the nerve fiber layer (NFL), pyknotic nuclei in the ganglion cell layer (GCL), and decreased cell populations particularly in the inner nuclear layer (INL) and GCL. The degree of degeneration was dependent on the duration of UVA exposure. The signs of degeneration decreased gradually and disappeared completely after the 14-day recovery period. In addition, p53-deficient medaka fish were more tolerant than were wild-type (Hd-rR) Japanese medaka. In conclusion, UV radiation induced neurodegeneration in the brain, spinal cord, and retina of adult Japanese medaka (Oryzias latipes) but their normal histological architecture reappeared in these tissues after 14 days.

Intravitreal steroids for the treatment of retinal diseases

Diabetic macular edema (DME), pseudophakic cystoid macular edema (CME), age-related macular degeneration (AMD), retinal vascular occlusion (RVO), and uveitis are ocular conditions related to severe visual impairment worldwide. Corticosteroids have been widely used in the treatment of these retinal diseases, due to their well-known antiangiogenic, antiedematous, and anti-inflammatory properties. Intravitreal steroids have emerged as novel and essential tools in the ophthalmologist's armamentarium, allowing for maximization of drug efficacy and limited risk of systemic side effects. Recent advances in ocular drug delivery methods led to the development of intraocular implants, which help to provide prolonged treatment with controlled drug release. Moreover, they may add some potential advantages over traditional intraocular injections by delivering certain rates of drug directly to the site of action, amplifying the drug's half-life, contributing in the minimization of peak plasma levels of the drug, and avoiding the side effects associated with repeated intravitreal injections. The purpose of this review is to provide an update on the use of intravitreal steroids as a treatment option for a variety of retinal diseases and to review the current literature considering their properties, safety, and adverse events.

Drug safety evaluation of intravitreal triamcinolone acetonide

INTRODUCTION

Triamcinolone acetonide (TA) is a steroidal drug that has been widely administered intravitreally for retinal and choroidal conditions. Safety of steroidal products for intraocular use is essential because of their risk of ocular adverse events. This review comprehensively discusses the safety of intravitreal administration of TA.

AREAS COVERED

This paper analyzes the mechanisms of action and key pharmacokinetic attributes and provides a discussion of the main clinical trials investigating clinical applications of intravitreal TA. The safety of intravitreal TA is evaluated through a search of the Medline database from 1980 to 2011. The most relevant literature on the safety of intravitreal TA is also discussed.

EXPERT OPINION

The complications of intravitreal TA therapy include secondary ocular hypertension in about 20 - 40% of eyes, steroid-induced cataract in about 15 - 20% of cases and postinjection infectious endophthalmitis and pseudoendophthalmitis in less than 1%. TA is an effective drug for various retinal and choroidal diseases when delivered intravitreally. It may imply an off-label use and it may be associated with ocular adverse events. Intravitreal TA is not associated with significant systemic safety risks.

Low-Concentration Infracyanine Green–Assisted Internal Limiting Membrane Peeling in Idiopathic Macular Pucker 25-Gauge Surgery

Purpose

To investigate the efficacy of 25-gauge infracyanine green–assisted idiopathic macular pucker surgery and to identify prognostic factors.

Methods

In this retrospective interventional case series, 83 patients with idiopathic macular pucker who underwent 25-gauge surgery with infracyanine green–assisted internal limiting membrane (ILM) peeling were retrospectively reviewed. Best-corrected visual acuity (BCVA) measurement, complete ophthalmologic evaluation, and optical coherence tomography were performed at baseline and during follow-up. Preoperative and postoperative prognostic factors were correlated with final visual outcomes.

Results

Mean follow-up was 10.5 months (range 3-44). Best-corrected visual acuity improved from 0.56±0.27 logMAR (±SD) to 0.26 ±0.18 logMAR (p<0.001); central retinal thickness decreased from 441±115 μm to 355±72 μm (p<0.001). Greater postoperative visual gain was correlated with baseline BCVA (r=–0.65, p<0.0001), and BCVA gain after 1 week (r=0.64, p<0.0001) and 1 month (r=0.58, p<0.0001). Final BCVA was influenced by baseline BCVA (r=0.46, p<0.0001), BCVA change after 1 month (r=0.34, p=0.002), and presence of intraretinal fluid (r=0.28, p=0.01). No cases of endophthalmitis, retinal tears, or retinal detachments were reported.

Conclusions

Low-concentration infracyanine green–assisted ILM peeling during minimally invasive surgery is associated with significant visual acuity improvement. Preoperative BCVA and optical coherence tomography appearance may be helpful in predicting the final visual outcome.

Toxicity of Indocyanine Green (ICG) in Combination with Light on Retinal Pigment Epithelial Cells and Neurosensory Retinal Cells

PURPOSE

To evaluate the toxicity of indocyanine green (ICG) in combination with light.

METHODS

Human retinal pigment epithelial cells (ARPE-19) and rat neurosensory retinal cells (R28) were treated with four different concentrations of ICG in combination with light exposure. Cell viability, mitochondrial function, and DNA synthesis were measured.

RESULTS

All concentrations of ICG with 10 min of light exposure caused a significant decrease in mitochondrial dehydrogenase activity in R28 and ARPE-19 cells. ICG without light exposure did not decrease mitochondrial dehydrogenase activity. In both cell lines, [(3)H]thymidine incorporation was increased when treated with ICG with or without light. R28 cells did not show any significant decrease in cell viability.

CONCLUSIONS

The duration of light was a significant factor in ICG toxicity. ICG needs to be used with caution as it decreases the mitochondrial dehydrogenase activity and increases the DNA synthesis in retinal cells, markers for cell toxicity and dysfunction.

Involvement of illumination in indocyanine green toxicity after its washout in the ex vivo rat retina

PURPOSE

To elucidate the involvement of illumination in indocyanine green (ICG) retinal toxicity.

METHODS

We incubated isolated rat retinas with or without illumination after exposure to 0.5% ICG. We also examined whether a time lag following ICG exposure before illumination altered the damage. Toxicity was evaluated by histologic and biochemical assays, including measurement of lactate dehydrogenase release.

RESULTS

Retinas fixed immediately after ICG exposure showed minimal morphologic changes. However, illumination for 3 hours at 34 degrees C starting after washout of ICG selectively damaged the outer nuclear layer. Retinas incubated for 3 hours under the same condition in the dark showed preserved morphology but were damaged by subsequent illumination. When retinas were illuminated after washout of ICG at a lower temperature (30 degrees C), the damage was attenuated. Results obtained using lactate dehydrogenase release were consistent with these morphologic changes.

CONCLUSIONS

Incubating retinas in the dark and cooling after ICG exposure significantly inhibited retinal damage, suggesting that ICG interacts with illumination to induce retinal damage.

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.

Effects of ascorbic acid on UV light-mediated photoreceptor damage in isolated rat retina

Concerns have been raised about whether operating microscopes and endoillumination used during ophthalmic surgeries contribute to retinal damage. Despite the recognition that ascorbic acid (vitamin C) helps to protect the eye from light and the abundance of vitamin C in the retina, artificial aqueous humors used during surgery only contain the antioxidant glutathione. To test whether inclusion of antioxidants other than glutathione in surgical solutions might help to preserve retinal integrity, we studied the effects of vitamin C on acute toxicity in isolated rat retinas. Male Sprague-Dawley rats (PND 30+/-2) were sacrificed for retinal isolation. In the presence or absence of vitamin C (1 or 3 mM), retinas were exposed to 302 nm ultraviolet B (UVB) light for 1 h and were incubated for a total of 5 h at 30 degrees C. Retinal damage was assessed by morphological examination and biochemical assay measuring the amount of lactate dehydrogenase (LDH) released from injured cells. In control retinas, LDH release was significantly increased after UVB exposure. The presence of 1 mM vitamin C in the incubation media significantly reduced LDH release during the post-incubation period following UV exposure. No difference was found between 1 and 3 mM vitamin C. Microscopic examination revealed that disorganization in the outer nuclear layer after UVB exposure was markedly attenuated by administration of 1 mM vitamin C. Vitamin C (1 mM), a concentration found in the anterior chamber in humans, but not glutathione, prevented phototoxic injury following UV exposure. Although vitamin C itself cannot be used in intraocular irrigating solutions because of adverse interactions with iron released during bleeding, inclusion of antioxidants equivalent to vitamin C should be considered to help protect the retina from intraoperative light toxicity.

Idiopathic macular hole surgery with low-concentration infracyanine green-assisted peeling of the internal limiting membrane

PURPOSE

To evaluate the efficacy of pars plana vitrectomy with infracyanine green (IFCG)-assisted internal limiting membrane peeling for the treatment of idiopathic macular hole.

DESIGN

Prospective, noncomparative interventional case series.

METHODS

Thirty-eight consecutive eyes of 35 patients with idiopathic macular hole were included in the study. Patients underwent early treatment diabetic retinopathy (ETDRS) visual acuity examination, dilated ophthalmoscopy, and optical coherence tomography before treatment and during follow-up. Fluorescein angiography was done in selected cases. Patients underwent a three-port pars plana vitrectomy with complete posterior hyaloid and epiretinal membrane removal. The internal limiting membrane (ILM) was stained with 0.5 cc of IFCG (0.5 mg/ml, 308 mOsm) and peeled up to the vascular arcades. Perfluoropropane gas (C(3)F(8)) 10% was used as tamponade.

RESULTS

Mean follow-up duration was 10 +/- 5 months (range, 3 to 24 months). Six eyes had stage 2 macular hole, 15 eyes stage 3, and 16 eyes stage 4. Overall, 37 of 38 macular holes closed after a single surgery. Median visual acuity was 20/100 (range, 20/400 to 20/50) before surgery and 20/50 (range, 20/640 to 20/25) after surgery. Visual acuity after surgery was 20/50 or better in 24 of 38 (63.1%) eyes. Twenty-five (65.8%) eyes improved by 2 or more lines, nine (23.7%) eyes were stable, and four (10.5%) eyes worsened by 2 or more lines.

CONCLUSIONS

This study suggests that IFCG (0.05%) effectively stains the ILM with apparent safety, and that IFCG-assisted peeling of the ILM may be useful in the treatment of idiopathic macular hole.

Age-Related Macular Degeneration: A Practical Approach to a Challenging Disease

Age-related macular degeneration (AMD) is the leading cause of blindness in older North Americans. The clinical spectrum, risk factors, pathophysiology, and potential therapeutic options for AMD warrant a careful review. Despite the growth in treatment options for this disease, there is no current curative therapy. Of critical importance is attention to modifiable risk factors--improvements in cardiovascular status, including smoking cessation, and routine ophthalmic monitoring for opportunities to provide early intervention. In addition, a low-vision assessment to investigate the potential use of visual assistive devices may be beneficial to any patient who has experienced a decrease in vision. Finally, education regarding the clinical course of age-related macular degeneration and accurate information with respect to the known benefits of available treatments will impart a better understanding of this disease to patients.

Intravitreal triamcinolone acetonide: a change in a paradigm

BACKGROUND

Based on experimental studies and clinical observations by Robert Machemer, Gholam Peyman and others, the vitreous cavity has increasingly been used as a reservoir of drugs for the direct treatment of intraocular diseases.

METHODS AND RESULTS

The most widely injected drug so far has been triamcinolone acetonide for various intraocular neovascular and edematous diseases. Comparing the various diseases with respect to effect and side effects of the treatment, the best response in terms of gain in visual acuity has been achieved for intraretinal edematous diseases such as diffuse diabetic macular edema, branch retinal vein occlusion, central retinal vein occlusion, and pseudophakic cystoid macular edema. In eyes with various types of noninfectious uveitis including acute or chronic sympathetic ophthalmia and Adamantiadis-Behçet's disease, visual acuity increased and the degree of intraocular inflammation decreased. Some studies have suggested that intra- vitreal triamcinolone may be useful as an angiostatic agent in eyes with iris neovascularization and proliferative ischemic retinopathies. Intravitreal triamcinolone may possibly be helpful as adjunct therapy for exudative age-related macular degeneration, particularly in combination with photodynamic therapy. In eyes with chronic, therapy-resistant ocular hypotony, intravitreal triamcinolone can induce an increase in intraocular pressure and may stabilize the eye. The complications of intravitreal triamcinolone therapy include secondary ocular hypertension in about 40% of the eyes injected; medically uncontrollable high intraocular pressure leading to antiglaucomatous surgery in about 1-2% of the eyes; posterior subcapsular cataract and nuclear cataract leading to cataract surgery in about 15-20% in elderly patients within 1 year after injection; postoperative infectious endophthalmitis with a rate of about 1:1,000; noninfectious endophthalmitis, perhaps due to a reaction to the solvent agent, and pseudoendophthalmitis with triamcinolone acetonide crystals appearing in the anterior chamber. Intravitreal triamcinolone injection can be combined with other types of intraocular surgery including cataract surgery, particularly in eyes with iris neovascularization. Cataract surgery performed some months after the injection does not show a markedly elevated complication rate. The injection may be repeated, if vision redecreases. In nonvitrectomized eyes, the duration of the effect and side effects of a single intravitreal injection of triamcinolone is about 6-9 months for a dosage of about 20 mg, and about 2-4 months for a dosage of 4 mg. It has remained unclear so far, whether and how to remove the solvent agent. In the future, intravitreal triamcinolone may be combined with other antiangiogenic drugs for the treatment of exudative age-related macular degeneration or with neuroprotective drugs for treatment of diabetic retinopathy.

CONCLUSIONS

Despite an exponentially increasing number of mostly case-series studies, the intravitreal injection of triamcinolone may still be considered an experimental procedure until randomized studies have been presented.

Intravitreal triamcinolone acetonide for treatment of intraocular oedematous and neovascular diseases

Intravitreal triamcinolone acetonide (IVTA) has increasingly been applied as treatment for various intraocular neovascular and oedematous diseases. Comparing the various diseases with respect to effect and side-effects of the treatment, the best response in terms of gain in visual acuity (VA) has been achieved for intraretinal oedematous diseases such as diffuse diabetic macular oedema, branch retinal vein occlusion, central retinal vein occlusion and pseudophakic cystoid macular oedema. In eyes with various types of non-infectious uveitis, including acute or chronic sympathetic ophthalmia and Adamantiadis-Behcet's disease, VA increased and the degree of intraocular inflammation decreased. Some studies have suggested that intravitreal triamcinolone may be useful as angiostatic therapy in eyes with iris neovascularization and proliferative ischaemic retinopathies. Intravitreal triamcinolone may possibly be helpful as adjunct therapy for exudative age-related macular degeneration (AMD), particularly in combination with photodynamic therapy. In eyes with chronic, therapy-resistant ocular hypotony, intravitreal triamcinolone can induce an increase in intraocular pressure (IOP) and may stabilize the eye. The complications of intravitreal triamcinolone therapy include: secondary ocular hypertension in about 40% of the eyes injected; medically uncontrollable high IOP leading to antiglaucomatous surgery in about 1-2% of the eyes; posterior subcapsular cataract and nuclear cataract leading to cataract surgery in about 15-20% of elderly patients within 1 year of injection; postoperative infectious endophthalmitis occurring at a rate of about one per 1000; non-infectious endophthalmitis, perhaps due to a reaction to the solvent agent, and pseudo-endophthalmitis with triamcinolone acetonide crystals appearing in the anterior chamber. Intravitreal triamcinolone injection can be combined with other intraocular surgeries, including cataract surgery, particularly in eyes with iris neovascularization. Cataract surgery performed some months after the injection does not show a markedly elevated complication rate. The injection may be repeated if the resultant benefits decrease after the initial IVTA injection. In non-vitrectomized eyes, the duration of the effect and side-effects of a single intravitreal injection of triamcinolone is about 6-9 months for a dosage of about 20 mg, and about 2-4 months for a dosage of 4 mg. So far, it has remained unclear whether the solvent agent should be removed, and if so, how.

An Ex-Vivo, Whole-Globe Porcine Model of Corneoepithelial Wound Healing Tested Using Immunomodulatory Drugs

BACKGROUND

An efficient epithelial wound healing is essential for the preservation of vision. Hence, the effects of novel topical drugs on the ocular surface must be ascertained before clinical use. We have tested the utility of an ex vivo, whole-globe porcine screening model to serve as a partial substitute for resource- and time-consuming animal experiments.

METHODS

Standardized corneoepithelial lesions, 5.0 mm in diameter and 40 microm in depth, were created with an Excimer laser in freshly enucleated porcine eyes. These were then exposed to control solutions (physiological saline (baseline), tissue-culture medium (positive control) and NH4 + (toxicity control)) and to three test agents (cyclosporin A, dexamethasone, and mitomycin C). The wound-healing response and toxic effects were monitored after 20-26 h by comparing lesion sizes.

RESULTS

According to baseline data obtained using physiological saline, tissue-culture medium improved wound healing. The highest doses of NH4 + (1 M) and mitomycin C (1.0 mg/mL) elicited toxic effects (confidence interval according to Scheffé's post hoc test: -0.65 to -0.07 and -0.99 to -0.60, respectively). Under the same test conditions, cyclosporin A (0.1 to 10 mg/mL) and dexamethasone (0.1 to 10 mg/mL) had no influence on corneoepithelial wound healing.

CONCLUSIONS

Drug screening with this ex vivo porcine model permits a reproducibly quantitative and time- and dose-dependent assessment of corneoepithelial wound healing. This model corresponds more closely to the clinical situation than cell culturing and may, therefore, be useful in evaluating novel pharmaceutical agents, thereby helping to cut down on the number of animal experiments performed prior to the instigation of clinical trials.

Use of trypan blue for penetrating keratoplasty

Use of trypan blue for penetrating keratoplasty was developed to facilitate the procedure. Trypan blue is injected before and after the addition of 0.25 mL of an ophthalmic viscosurgical device (OVD), sodium hyaluronate, to stain the internal and external cut edge of the cornea as well as the OVD, enabling the surgeon to improve visualization of the incision and suture depth, improve alignment of host and donor tissues, and ensure that all OVD is removed.