Effects of pegaptanib sodium on retinal function in isolated perfused vertebrate retina.

PURPOSE: To evaluate the short-term toxic effects of pegaptanib sodium on retinal function. At present, intraocular anti-vascular endothelial growth factor (VEGF) therapy is the primary choice of treatment for neovascular maculopathy. The isoform VEGF(165) is specifically inhibited by pegaptanib sodium. Therefore, since VEGF(165) has neuroprotective effects against apoptosis of neuronal cells, blockage of VEGF(165) by pegaptanib could induce retinal dysfunction. In the present study, we used an electrophysiological technique for testing retinal toxicity in order to evaluate the short-term toxic effects of pegaptanib sodium on retinal function in a model of isolated perfused vertebrate retina. METHODS: Isolated bovine retinas were perfused with an oxygenated, pre-incubated nutrient solution. Electroretinograms (ERGs) were recorded as trans-retinal potentials using Ag/AgCl electrodes. Pegaptanib sodium (0.006, 0.06, or 0.2 mg/ml) and solvent carrier were added to the nutrient solution for 45 min. ERGs were monitored before, during, and after exposure. RESULTS: No significant reductions of b-wave (p = 0.357, p = 0.31, and p = 0.11, respectively) or a-wave (p = 0.189, p = 0.46, and p = 0.23, respectively) amplitudes were detected during application of pegaptanib (0.006, 0.06, or 0.2 mg/ml). The solvent carrier alone had no effect on ERG b- or a-waves (p = 0.98 and p = 0.42, respectively). During washout, ERG amplitudes of all test series remained unchanged. CONCLUSION: Results suggest that both pegaptanib sodium and its solvent carrier have good safety profiles. Intraocular application of 0.3 mg pegaptanib sodium induced no significant changes in ERGs in our ex vivo model and, thus, appears to be safe.

The effects of triamcinolone crystals on retinal function in a model of isolated perfused vertebrate retina.

A good clinical experience of intravitreal triamcinolone acetonide (TA) has been reported in several studies, but there are growing indications that epiretinal crystals of TA exhibit retinal toxicity. To investigate the effects of TA on retinal function we used a model of an electrophysiological in vitro technique for testing retinal toxicity. Isolated bovine retinas were perfused with an oxygen saturated nutrient solution. The electroretinogram (ERG) was recorded as a transretinal potential using Ag/AgCl electrodes. After reaching stable ERG-amplitudes TA at the maximum solubility equilibrium (36 microg/ml) was either applied to the nutrient solution for 45 min or TA was administered epiretinally at concentrations (1 mg/ml, 4 mg/ml, 8 mg/ml, 20 mg/ml and 40 mg/ml) above the maximum solubility equilibrium to assure direct contact of the TA crystals with the isolated perfused retinas. After that the retinas were reperfused for 75 min with the standard nutrient solution. The percentage of a- and b-wave reduction directly after the application and at the washout was calculated. To assess the effects of TA at the level of the ganglion cell layer a Viability/Cytotoxicity Kit for mammalian cells was used. No changes of the ERG-amplitudes were detected during the exposure to 36 microg/ml TA for 45 min (b-wave: 9.6 microV+/-2.1 vs. 8 microV+/-2.1 (p=0.135); a-wave: -11 microV+/-2.7 vs. -10.6 microV+/-2.3 (p=0.889)) and at the washout (b-wave: 8 microV+/-2.1 vs. 8.3 microV+/-2.4 (p=0.18); a-wave: -10.6 microV+/-2.3 vs. -12 microV+/-2.6 (p=0.225)). At concentrations higher than 1mg/ml TA induced a decrease of the a- and b-wave in a concentration dependent manner. These changes were reversible for concentrations of TA up to 20mg/ml (b-wave: 9 microV+/-2.4 vs. 6.6 microV+/-2.5 (p=0.08); a-wave: -11.4 microV+/-2.0 vs. -11.2 microV+/-2.2 (p=0.37)), but irreversible at 40 mg/ml even at the end of the washout (b-wave: 9.8 microV+/-1.9 vs. 3 microV+/-1.7 (p=0.009); a-wave: -9.8 microV+/-2.1 vs. -2.6 microV+/-2.1 (p=0.001)). Histological examination of the preparations revealed a dramatic ganglion cell death, in which an application of 20mg/ml and 40 mg/ml TA led to a 60.53% (p=0.013) and 82.35% (p=0.002) ganglion cell death, respectively. The epiretinal application of 4 mg/ml TA and higher resulted in distinct effects on the ERG of the isolated perfused retinas. Ganglion cell death was induced at a concentration of 20mg/ml and higher. TA shows an asymmetric and partly high concentrated distribution after intravitreal application. Therefore, we consider concentrations of 4 mg/ml and higher might be toxic and should be avoided in clinical use.

Self-application of single-use eyedrop containers in an elderly population: comparisons with standard eyedrop bottle and with younger patients.

PURPOSE: To test whether patients aged >or=80 years can safely and successfully apply eyedrops from a single-use eyedrop container without support, and to compare the results with those of younger patients using single-use containers and older patients using standard eyedrop bottles. METHODS: Patients aged >or=80 years who had no physical or mental conditions hindering self-application of eyedrops and actually did so because of glaucoma or dry eyes were included consecutively in the study group (n = 44) in order to perform self-application of eyedrops from single-use eyedrop containers. Patients were observed meticulously by two investigators, who documented practical problems during the procedure in a checklist. In control group A (n = 22), glaucoma or sicca patients aged between 50 and 65 years applied drops from single-use eyedrop containers; in control group B (n = 28), glaucoma or sicca patients aged >or=80 years used a traditional eyedrop bottle. RESULTS: Successful application of the drops into the conjunctival sac was achieved by 57% in the study group (95% and 89% in control groups A and B, respectively). Scratching of the eyedrop container along the conjunctiva or cornea was observed in 68% of the study group (41% and 61% in control groups A and B, respectively). Frequency of problems during opening and self-application of single-use eyedrop containers in the study group showed an inverse correlation to visual acuity in the better eye and previous experience with this kind of eyedrop container. CONCLUSION: Older patients have massive problems in self-administering eyedrops from single-use containers. Factors influencing the success of self-application may include the patient's previous experience with this kind of eyedrop container and the patient's visual acuity.

A prospective trial of phaco-trabeculotomy combined with deep sclerectomy versus phaco-trabeculectomy.

BACKGROUND: Combined phacoemulsification, intraocular lens implantation, and trabeculectomy (PTE) is currently the standard procedure for most ophthalmic surgeons to treat uncontrolled open-angle glaucoma and cataract at one time. This study was designed to prospectively compare a new technique of phaco-trabeculotomy plus deep sclerectomy (PDSTO) with standard phaco-trabeculectomy (PTE). METHODS: A consecutive series of 43 patients with uncontrolled open-angle glaucoma and cataract underwent combined glaucoma and cataract surgery. The procedure started as a two-site approach with phacoemulsification and IOL implantation through a temporal incision in clear cornea. Trabeculotomy and deep sclerectomy were performed in the superior quadrant. Trabeculectomy was also performed in the superior quadrant as a modified Cairns trabeculectomy. Postoperatively, examinations were performed on a daily base for 1 week. Follow-up visits were applied 1, 3, 6, and 12 months after surgery. RESULTS: The mean preoperative intraocular pressure (IOP) was 26.5 mmHg (SD 7.8) for all patients enrolled. The mean IOP was 12.3 mmHg (SD 5.1) 1 day post surgery for the PTE group (p < 0.001) and 14.4 mmHg (SD 4.0) for the PDSTO group (p < 0.001). At 12 months post surgery the success rate according to the Advanced Glaucoma Intervention Study (AGIS), defined as an IOP lower than 18mmHg without medication, was 20% in the PTE group and 50% in the PDSTO group (p = 0.03). The number of postoperative complications was equally low for both groups. No severe complications, such as bleb infection, endophthalmitis, or choroidal hemorrhage were seen in this series. CONCLUSIONS: PDSTO offered significant IOP reduction and a success rate which was higher than that of the current standard, PTE. The specific intra- and postoperative complications of deep sclerectomy, trabeculotomy, and trabeculectomy were seen in our series, although the overall rate of postoperative complications proved low.

Combined cataract-glaucoma surgery using the intracanalicular Eyepass glaucoma implant: first clinical results of a prospective pilot study.

PURPOSE: To study prospectively the safety and pressure-reducing efficacy of the Y-shaped Eyepass glaucoma implant (GMP Vision Solutions, Inc.). SETTING: Departments of Ophthalmology, University of Cologne, Cologne, and University of Erlangen, Erlangen, Germany. METHODS: This study comprised 12 patients with primary open-angle or exfoliative glaucoma and cataract who had phacoemulsification with endocapsular implantation of a foldable intraocular lens and intracanalicular implantation of an Eyepass glaucoma implant. The implant is a silicone microtube shunt that bypasses the trabecular meshwork and connects the lumina of Schlemm canal with the anterior chamber in combined cataract-glaucoma surgery. Perioperative complications, intraocular pressure (IOP), and pressure-reducing topical medications were monitored over a preliminary follow-up. RESULTS: Perforation of the trabecular meshwork during Eyepass implantation occurred in 2 eyes; the antiglaucoma procedure was converted to trabeculotomy after the shunt was explanted, and both eyes were excluded from further follow-up. In the remaining 10 eyes, the mean maximum IOP was 30.4 mm Hg +/- 7.5 (SD) (range 21 to 46 mm Hg) preoperatively, 12.0 +/- 6.1 mm Hg (range 2 to 20 mm Hg) 1 day postoperatively, 17.2 +/- 4.1 mm Hg (range 12 to 27 mm Hg) at 4 weeks, and 18.3 +/- 4.5 mm Hg (range 12 to 25 mm Hg) at the end of the preliminary follow-up. The mean number of topical medications was 3.2 +/- 0.8 preoperatively and 0.9 +/- 0.7 at the end of follow-up (mean 7.1 months). Although there were no major complications requiring surgical revision, 4 eyes had an IOP of 18 or higher at the end of follow-up. CONCLUSION: Combined cataract surgery with Eyepass shunt implantation was safe and appeared to be beneficial in glaucomatous eyes with cataract not requiring a low target IOP.

Electrophysiological effects of Brilliant Blue G in the model of the isolated perfused vertebrate retina.

BACKGROUND: To facilitate epiretinal or inner limiting membrane peeling dyes like Indocyanine Green (ICG) as well as Trypan Blue (TB) were used so far. However, toxic effects on the retina were described for both dyes. The aim of our study was to investigate the retinal tolerance to the new dye Brilliant Blue G (BBG), which implies a possibly more favorable biocompatibility. METHODS: Bovine retina preparations were perfused with an oxygen preequilibrated standard solution. The electroretinogram (ERG) was recorded using Ag/AgCl-electrodes. After recording stable b-wave amplitudes, Brilliant Blue G (BBG) was applied epiretinally for 10 s, 15 s, 30 s, 60 s and 120 s at a concentration of 0.25 mg/ml, which was recently proposed for vitreoretinal surgery. To disclose the effects of BBG on photoreceptor function two test series at the same concentration were performed to evaluate the impact of BBG 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, BBG was epiretinally applied for 30 s or 60 s. The recovery of the ERG-amplitudes was followed up for 115 min. RESULTS: Reductions of the a- and b-wave amplitude were found directly after exposure with BBG in each test series, but the effects on the electroretinogram after application of BBG were rapidly and completely reversible within the recovery time for all exposure times. No differences were found between the ERG-amplitudes before and after dye application at the end of the washout. CONCLUSIONS: BBG seems to be an alternative vital staining dye with a good biocompatibility. Comparing the effects with Indocyanine Green or Trypan Blue in the model of the isolated perfused vertebrate retina BBG exhibits a more favorable safety profile.

Mitomycin C induces multidrug resistance in glaucoma surgery.

BACKGROUND: Despite the adjuvant use of mitomycin C during trabeculectomy, failures still occur. We investigated whether cultured human Tenon fibroblasts exposed to low-dose mitomycin C developed a multidrug resistance phenotype in vitro, and whether mitomycin C treatment during previous filtration surgery induces P-glycoprotein expression in vivo. METHODS: Cultured human Tenon fibroblasts treated with low-dose 0.01 nM mitomycin C for 2 weeks were subsequently treated with 0.1 to 100 microM mitomycin C in the absence or presence of 4 microM verapamil, and allowed to recover for 24 hours. Low-dose mitomycin C-treated fibroblasts were analysed for P-glycoprotein expression using flow cytometry, immunoblotting, and RT-PCR for mdr-1 mRNA. In addition, fibroblasts were treated with low dose 0.1 nM 5-fluorouracil for 2 weeks and analysed for P-glycoprotein expression using flow cytometry. Expression of P-glycoprotein was analysed in surgically removed Tenon tissue (n = 30) using immunohistochemistry. Of the 30 patients, 20 had a previous trabeculectomy, of which nine had previous adjuvant therapy with mitomycin C during trabeculectomy. RESULTS: Partial resistance to mitomycin C after low-dose mitomycin C pre-treatment was significantly neutralised by the addition of verapamil. Low-dose mitomycin C up-regulated P-glycoprotein expression, but not mdr-1 mRNA expression. 5-Fluorouracil did not induce P-glycoprotein expression. P-glycoprotein expression was detected in all nine patients exposed to mitomycin C during previous trabeculectomies. Only six of 21 specimens from patients not previously exposed to mitomycin C showed faint P-glycoprotein expression. CONCLUSION: The induction of P-glycoprotein by mitomycin C could explain some failures that occur after repeated use of mitomycin C during trabeculectomy. The concomitant use of verapamil or the use of 5-fluorouracil alone could increase the success rate of repeat trabeculectomies.

The effects of the phosphodiesterase type V inhibitor sildenafil on human and bovine retinal function in vitro.

BACKGROUND: After the ingestion of sildenafil (Viagra), visual adverse events have been reported, possibly caused by an inhibition of the phototransduction cascade by sildenafil via phosphodiesterase (PDE 6). Therefore, we investigated the effects of sildenafil on photoreceptors and postsynaptic neurons of human and bovine retinas using the isolated superfused vertebrate retina technique. METHODS: Human and bovine retina preparations were perfused with an oxygen preequilibrated standard solution. The electroretinogram (ERG) was recorded using Ag/AgCl electrodes. After recording stable ERG amplitudes, sildenafil was added to the solution for 45 min. Thereupon, the preparations were reperfused with standard solution for 240 min. RESULTS: Following the application of sildenafil (3 microMol/l), the b-wave amplitude of bovine and human preparations was reduced continuously and disappeared completely. After reperfusion with the standard solution for 4 h, the b-wave amplitude did not recover completely. Using the same sildenafil concentration (3 microMol/l), the a-wave amplitude of the human retina was not totally abolished, but reduced to 21% of the initial amplitude and remained reduced at washout. For all retinal preparations, the implicit time of the ERG amplitudes remained significantly extended at the end of the washout. CONCLUSIONS: Strong similarities were detected in the drug-induced changes of the ERG when comparing human and bovine retinas. The results suggest that sildenafil impairs retinal function at not only the level of the photoreceptors, but it also affects the neuronal network of the inner retina at concentrations of approximately 30-fold higher than at therapeutic plasma concentrations.

In vivo retinal tolerance of various heavy silicone oils.

PURPOSE: Heavy silicone oils are currently under investigation as a permanent tamponade in eyes with inferior PVR. This study was an investigation of Densiron 68 (Fluoron GmbH, Neu-Ulm, Germany) and several new heavy silicone oil admixtures on the basis of the perfluoroalkanes F4H5 (perfluorobutylpentane), F4H6 (perfluorobutylhexane), and F4H8 (perfluorobutyloctane) with respect to their long-term tolerance in a rabbit model. METHODS: Because of the better solubility of the F4Hn-species (n = 5-8) in comparison to F6H8, we used F4H5, F4H6, and F4H8 to generate highly viscous, heavy silicone oils (HSO). After vitrectomy and fluid-air exchange, the left eye of each of five rabbits per group was filled with HSO 68-1500 (Densiron 68), HSO 45-5000, HSO 45-3000, HSO 46-5000, HSO 46-3000, HSO 48-5000, or HSO 48-3000, or pure F4H5, F4H6, or F4H8. Detailed clinical investigation, ERG testing, and histologic evaluation were performed throughout a 3-month follow-up. RESULTS: Densiron 68 and HSOs based on F4H5, as well as the three control oils (silicone oil of 1000, 3000, and 5000 mPa . s) were well tolerated over 3 months. Histologically, the retina was unaffected. In contrast, intraocular inflammation, cataract formation, and retinal detachment and degeneration were noticed in all groups with HSOs based on F4H6 or F4H8. CONCLUSIONS: Biocompatibility of the new HSOs is dependent on the lipophilic behavior (R(F)/R(H) ratio) and furthermore on the molecular dimension of the used semifluorinated alkanes (SFAs). HSOs on the basis of F4H5 may have advantages over silicone oils, on the basis of F6H8, for use as a tamponade agent for the inferior retina in difficult retinal situations.

The retinal tolerance to bevacizumab in co-application with a recombinant tissue plasminogen activator.

AIM: To investigate the retinal toxicity of bevacizumab in co-application with a commercially available recombinant tissue plasminogen activator (rt-PA), and to facilitate a new therapeutic concept in the treatment of massive subretinal haemorrhage caused by neovascular age-related macular degeneration (AMD). METHODS: Isolated bovine retinas were perfused with an oxygen-preincubated nutrient solution. The electroretinogram (ERG) was recorded as a transretinal potential using Ag/AgCl electrodes. Bevacizumab (0.25 mg/ml) and rt-PA (20 microg/ml) were added to the nutrient solution for 45 min. Thereafter, the retina was reperfused for 60 min with normal nutrient solution. Similarly, the effects of rt-PA (20 microg/ml, 60 microg/ml and 200 mug/ml) on the a- and b-wave amplitudes were investigated. The percentages of a- and b-wave reduction during application and at washout were calculated. RESULTS: During application of bevacizumab (0.25 mg/ml) in co-application with 20 microg/ml (rt-PA), the ERG amplitudes remained stable. The concentrations of rt-PA alone (20 microg/ml and 60 microg/ml) did not induce significant reduction of the b-wave amplitude. In addition, 20 microg/ml rt-PA did not alter the a-wave amplitude. However, 60 microg/ml rt-PA caused a slight but significant reduction of the a-wave amplitude. A full recovery was detected for both concentrations during the washout. At the highest tested concentration of 200 microg/ml rt-PA, a significant reduction of the a- and b-wave amplitudes was provoked during the exposure. The reduction of ERG amplitudes remained irreversible during the washout. CONCLUSION: The present study suggests that a subretinal injection of 20 microg/ml rt-PA in co-application with bevacizumab (0.25 mg/ml) for the treatment of massive subretinal haemorrhage seems possible. This is a safety study. Therefore, we did not test the clinical effectiveness of this combined treatment.

Truncating mutation of the DFNB59 gene causes cochlear hearing impairment and central vestibular dysfunction.

We have identified a consanguineous family from Morocco segregating autosomal recessive congenital progressive hearing loss (ARNSHL) and retinal degeneration. Detailed clinical investigation of the six siblings revealed combined severe cone-rod dystrophy (CORD) and severe/profound hearing impairment in two of them, while there is isolated CORD in three and nonsyndromic profound hearing loss in one. We therefore assumed a partial overlap of two nonsyndromic autosomal recessive conditions instead of a monogenic syndrome and performed genomewide linkage analysis. The disease loci were mapped to chromosome 2q31.1-2q32.1 for ARNSHL and to 2q13-2q14.1 for CORD, respectively. The retinal phenotype was shown to be due to homozygosity for a novel splice site mutation, c.2189+1G>T, in the retinitis pigmentosa gene MERTK. The ARNSHL interval comprised the DFNB59 locus. The DFNB59 gene has been identified recently, and two missense mutations (p.R183W and p.T54I) have been shown to cause auditory neuropathy in both humans and transgenic mice. Mutation screening in the DFNB59 gene in our family revealed homozygosity for a 1-bp insertion in exon 2 (c.113_114insT), predicting a truncated protein of 47 amino acids, in all three hearing impaired subjects. This is the first description of biallelic putative loss-of-function of the DFNB59 gene. Detailed audiological investigation clearly indicated hair cell dysfunction and, in contrast to cases reported previously, excluded auditory neuropathy. We show that besides otoferlin (OTOF), DFNB59 is the second known gene in which mutations can result in these two distinct forms of hearing impairment. Moreover, all patients in our family with homozygosity for the DFNB59 mutation display central vestibular dysfunction.

Phaco-trabeculotomy combined with deep sclerectomy, a new technique in combined cataract and glaucoma surgery: complication profile.

PURPOSE: Combined phacoemulsification, intraocular lens implantation and trabeculectomy (PTE) is currently the standard procedure for most ophthalmic surgeons for treating uncontrolled open-angle glaucoma and cataract at the same time. The present pilot study was designed to prospectively evaluate outcomes in glaucoma patients who underwent a new technique of phaco-trabeculotomy plus deep sclerectomy, with particular attention to the complication profile. METHODS: A consecutive series of 15 patients with uncontrolled open-angle glaucoma and cataract underwent combined glaucoma and cataract surgery. The procedure started as a two-site approach with phacoemulsification and intraocular lens (IOL) implantation through a temporal incision in clear cornea. Trabeculotomy and deep sclerectomy were performed in the superior quadrant. Postoperative examinations were performed daily for 1 week. Follow-up visits were carried out at 1, 3, 6 and 12 months after surgery. RESULTS: At 1 day post-surgery, mean intraocular pressure (IOP) was significantly reduced to 14.2 mmHg (SD 4.4). At 12 months post-surgery, the complete success rate, defined as IOP < 22 mmHg without medication, was 60%. Qualified success was achieved in 93.3% of patients. At 12 months post-surgery, the mean number of antiglaucoma medications had fallen to 0.4 (SD 0.6) (p < 0.001). Visual acuity improved by a mean value of 1.6 lines (SD 2.4) over baseline (p = 0.021). Specific complications such as choroidal deroofing, inadvertent perforation of the trabeculo-descemetic membrane, and non-identification of Schlemm's canal were seen among the patients in our trial. The incidence of complications due to overfiltration was low. A relatively high incidence of hyphaemas (53%) was noted in this series. All the hyphaemas were trivial and resolved quickly. No severe complications, such as bleb infection, endophthalmitis or choroidal haemorrhage were seen in this series. CONCLUSIONS: Phaco-trabeculotomy plus deep sclerectomy offered significant IOP reduction and a success rate that may be comparable with that of the current standard, PTE. Intra- and postoperative complications specific to deep sclerectomy and trabeculotomy were seen in our series, although the overall rate of postoperative complications proved low. Prospective comparative trials are needed to assess which of PTE and phaco-trabeculotomy plus deep sclerectomy is more successful.

Cyclodialysis ab interno as a surgical approach to intractable glaucoma.

PURPOSE: In glaucoma filtration surgery, the problem of subconjunctival scarring has still not been satisfactorily solved. Suprachoroidal drainage of aqueous humour offers a promising, alternative option for intractable glaucoma. We here present a clinical study on the surgical approach of gonioscopic cyclodialysis ab interno. PATIENTS AND METHODS: Twenty-eight eyes of 20 patients with intractable glaucoma were included in this prospective, consecutive, case-control study. The eyes had had a mean of 4.4 +/- 2.4 previous antiglaucomatous interventions. Baseline intraocular pressure (IOP) was 34.3 +/- 10.5 mmHg despite maximum therapy. Under gonioscopic control, cyclodialysis ab interno was performed over two clock times to gain access to the suprachoroidal space. No additional trabecular meshwork surgery was performed. Success was defined as a lowering of IOP to below 21 mmHg without the need for further medication or intervention. RESULTS: Mean postoperative IOP was 14.6 +/- 12.4 mmHg. Mean follow-up (FU) for all eyes was 121.8 days. After a mean of 60 days, 21 eyes (75%) needed further surgical intervention. Qualified success was seen in four eyes (14.3%), with a mean FU of 383.6 days. Three eyes (10.7%) showed absolute success after a mean FU period of 202.7 days. In our series, we obtained the best results for phakic eyes, followed by pseudophakic and aphakic eyes. CONCLUSION: The results of this study do not provide convincing evidence of the functional efficacy of cyclodialysis ab interno. Nevertheless, the technique is easy to perform and offers safe and atraumatic access to the resorptive capability of the choroid. Conjunctival manipulation is avoided. Contrary to reports in the current literature, in our series, the best results were obtained for phakic eyes, though the small number of eyes included does not allow reliable statistics. Further studies will need to focus on the use of different space-retaining substances or a widening of the cyclodialysis cleft to improve surgical outcome.

Effects of the protein tyrosine kinase inhibitor genistein and taurine on retinal function in isolated superfused retina.

BACKGROUND: Genistein has the potential to act as an intraocular antiangiogenic agent. Its therapeutical use, however, is limited by toxic side effects on the retina. This study was designed to evaluate the simultaneous use of taurine as a neuroprotective drug. METHODS: Bovine retinas were isolated and perfused with an oxygen-preincubated nutrient solution. The electroretinogram (ERG) was recorded as a transretinal electrical potential using Ag/AgCl electrodes. At stable ERG amplitudes, genistein at concentrations of 11, 37, and 150 microM was added to the nutrient solution for 45 min, in the absence or presence of taurine (3 mM). Thereafter, the retina was reperfused with the nutrient solution for another 100 min. The percentage of b-wave reduction during genistein and genistein/taurine application was calculated. RESULTS: The b-wave amplitude was reduced by a smaller amount during the application of genistein (11 and 37 microM) in the presence of taurine compared with genistein alone. For both, genistein/taurine and genistein alone the b-wave recovered completely during the wash-out of the drugs. However, during the application of the highest tested concentration of genistein (150 microM), taurine did not protect completely, leading to an irreversible b-wave reduction. CONCLUSIONS: The adjuvant use of taurine reduces the genistein-induced retinal toxicity to a certain degree. However, the protective effect of taurine is limited and there is only a narrow therapeutic index for a combined intravitreal administration of genistein in coapplication with taurine to inhibit pathological ocular neovascularization.

Effect of gravity in long-term vitreous tamponade: in vivo investigation using perfluorocarbon liquids and semi-fluorinated alkanes.

PURPOSE: In order to investigate whether gravity is the reason for retinal degeneration in long-term vitreous tamponade, perfluorohexyloctane (F6H8), perfluorodecalin (PFD), and a mixture of F6H8/PFD were compared. MATERIALS AND METHODS: Each group of 5 rabbits received a 3-month tamponade with either PFD (pure) (1.93 g/cm(3)), F6H8 (pure) (1.33 g/cm(3)), or a 1:1 mixture of F6H8/PFD (1.62 g/cm(3)). Electroretinograms (ERG) were performed pre- and postoperatively. Lower and upper retinal areas were compared using immunohistochemical methods. Transmission electron microscopy was performed to investigate alterations in the photoreceptors. RESULTS: All three substances were tolerated well in rabbit eyes for up to 3 months. Dispersion was seen earliest with PFD and latest with pure F6H8. None of the substances demonstrated inflammatory reactions or vascular alterations. ERGs were not considerably altered with any of the substances. Histology of the retina showed alterations in the cell counts within the inner and outer nuclear layer that were not attributable to the gravity of the tamponading agent. CONCLUSION: In contrast to previously published work, this study did not detect any tamponade-related structural damage of the retina after a 3-months tamponade in the rabbit model. Based upon this study, we conclude that gravity might not be causally linked to retinal damage.

The isolated perfused bovine retina--a sensitive tool for pharmacological research on retinal function.

The electroretinogram (ERG) of the isolated bovine retina serves as a proven criterion of retinal activity. It is used as a sensitive pharmacological tool for testing effects of applied drugs and toxins on photoreceptors, and higher order neurons that contribute to the generation of the b-wave. Following isolation and detachment from the underlying pigment epithelium, part of the retina was mounted into a closed chamber and perfused by a nutrient solution. Flow rate of the nutrient solution and its ingredients, incubation temperature and light intensity were optimised empirically to achieve a maximum b-wave amplitude. Under these conditions, a reproducible, high-resolution ERG can be stably recorded for more than 10 h with sufficient oxygenation found to be a prerequisite for the long-lasting stability. Addition of L(+)glutamate to the nutrient solutions was not anymore beneficial for the b-wave amplitude. A well-known inhibitor of oxidative phosphorylation (KCN) and antagonists of voltage-gated Ca2+ channels (isradipine, omega-conotoxin-GVIA and NiCl2) were used to prove the validity of the test system. The recording of the ERG from the isolated and perfused bovine retina serves as a valuable physiological model for a neuronal network in which important questions related to the retinal signalling and metabolism can be investigated.

Effects of phosphodiesterase type 5 inhibitor sildenafil on retinal function in isolated superfused retina.

After the oral ingestion of sildenafil, visual abnormalities have been reported constantly. The mechanism of these adverse events has been presumed to be a result of the interaction of sildenafil with the retinal phosphodiesterase (PDE) type 6. To investigate the physiological basis of the effects of sildenafil on retinal function, bovine retinas were isolated and perfused with an oxygen pre-equilibrated standard solution. The electroretinogram (ERG) was recorded as a transretinal potential using silver/silver-chloride electrodes. After reaching stable ERG amplitudes, sildenafil was added to the nurient solution at different concentrations, and its effect on the a- and b-wave amplitude was studied separately. The 0.1 microM and higher concentrations of sildenafil reduced the b-wave amplitude, while a reduction of the a-wave amplitude was observed at an elevated threshold of 0.3 microM. The changes of the ERG amplitudes were fully reversible for the b-wave at a concentration of 0.1 microM and for the a-wave at 0.3 microM sildenafil. At higher concentrations, sildenafil was found to be only partially reversible within recovery time. In conclusion, besides an inhibitory influence on photoreceptors, sildenafil performs additional effects on the postsynaptic neuronal network. Higher concentrations of sildenafil were found to have a potential for retinal degeneration, suggesting that further trials should be designed to evaluate the long-term effects of sildenafil. The physiological consequences of an abuse or long-term, daily use of sildenafil are not clear.

Signal quality of biometry in silicone oil-filled eyes using partial coherence laser interferometry.

PURPOSE: To assess the practical feasibility and signal quality of axial length measurements by partial coherence laser interferometry in silicone oil-filled eyes with previous complicated vitreoretinal surgery. SETTINGS: Department of Ophthalmology, University Cologne, Cologne, Germany. METHODS: Using a Zeiss IOLMaster, axial length measurements and signal-to-noise ratios of optical biometry in silicone oil-filled eyes (n=45) and contralateral eyes without tamponade (n=41) were analyzed. RESULTS: Axial length measurements with signal-to-noise ratio > or =2 were feasible in 41 of 45 silicone oil-filled eyes (91%) and 37 of 41 eyes without tamponade (90%). Cataract, central retinal detachment, vitreous hemorrhage, and emulsified oil droplets attached to the intraocular lens were reasons for failure of partial coherence laser interferometry. The signal-to-noise ratio of the first 2 measurements was significantly smaller (P=.04) in silicone-filled eyes (4.4 +/- 2.0) than in eyes without tamponade (5.5 +/- 3.0). Axial lengths of the oil-filled eye and the contralateral eye showed a significant intraindividual correlation (P<.0001, Spearman r=0.84). CONCLUSIONS: Partial coherence laser interferometry shows good clinical practicability in silicone oil-filled eyes with previous complicated vitreoretinal surgery. Further studies are needed to assess the reliability of these measurements with regard to postoperative refraction after combined oil removal and cataract surgery.

Effects of daunorubicin and CD95L on retinal function in superfused vertebrate retina.

Alternative treatments of proliferative vitreoretinopathy (PVR) are needed. The intravitreal application of daunorubicin combined with CD95 ligand (CD95L) could provide a new therapeutic strategy. The effects of this application on bovine retinal function were investigated. Bovine retina preparations were perfused with a standard solution preequilibrated with oxygen. The b-wave and, after the addition of aspartate, the photoreceptor potential P III of the electroretinogram (ERG) were recorded using Ag/AgCl electrodes. Stable ERG amplitudes were recorded, then daunorubicin was added to the solution for 45 minutes, also with the addition of CD95L antibody. Subsequently, the preparation was reperfused with the standard solution for 100 minutes, to allow for recovery. The reduction in b-wave amplitude was reversible and not significantly changed by the addition of 0.25 microg/mL CD95L antibody to 13 microM of daunorubicin. The reduction of the b-wave amplitude was significantly changed and only partly reversible within the recovery time using 40 microM and 80 microM of daunorubicin. The photoreceptor potential P III amplitude was not significantly changed for up to 80 microM of daunorubicin. The ERG showed toxic effects of daunorubicin above a concentration of 13 microM used therapeutically in humans. The combination with CD95L did not increase retinal toxicity. It is, therefore, concluded that daunorubicin may be applied intraocularly, combined with CD95L, without interfering with retinal function.