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Calcification of hydrophilic intraocular lenses (IOL) is a rare complication. We report about the uneventful replacement of an opacified hydrophilic IOL. The patient presented 4 years after uneventful cataract surgery with a reduction of visual acuity due to calcification of the IOL. Macroscopically, the optic and the haptics were opacified. Light and scanning electron microscopy revealed granular deposits on the external surface of the IOL and numerous fine granular deposits within the optic of the IOL which were distributed in a line parallel to the surface of the IOL.

For human trials with retinal prostheses it is mandatory to develop procedures to safely explant and possibly reimplant the devices. This prompted us to investigate in a small exploratory study the safety of repeated transchoroidal implantation and explantation procedures of complex subretinal devices in laboratory animals.Repeated transchoroidal surgery was performed in four rabbits. The rabbits were examined by clinical examination and funduscopy. Function was assessed by electroretinography and cortical recordings following light and subretinal electrical stimulation. Sections of the retina and of the implantation channel were examined by light microscopy.Using the same access route, repeated transchoroidal subretinal implantation surgery was successfully performed in all cases. Fixation of implants was stable for up to 13 months; retinas remained attached at all examination dates. Electroretinograms and visual evoked cortical potential proved retinal and visual pathway integrity. Subretinal electrical stimulation elicited retinal and cortical responses. While retinal morphology at earlier stages was found to be essentially unaltered, atrophic disorganization in the region of the subretinal channel was observed after 10 months and after subretinal electrical stimulation.Repeated transchoroidal surgery can be safely performed for implantation, explantation, and reimplantation of subretinal devices in rabbits. With modifications, we believe the technique can be applied in human surgery.

Purpose To evaluate the cleavage plane, corneal cytoarchitecture, and cell vitality of separated corneal epithelial sheets created with 3 commonly used microkeratomes. Setting Laboratories of the Regensburg University Medical Center, Regensburg, Germany. Methods Mechanical separation of the epithelial layer in 10 porcine eyes and 2 human eyes was performed with 3 different microkeratomes (Amadeus II, Zyoptix XP, Epivision). Five of 10 porcine corneas and the 2 human corneas treated with each microkeratome were processed for histology, electron microscopy, and immunohistochemistry. In 5 of 10 porcine corneas, the corneal epithelial sheets were separated from the globe and cell vitality was assessed with the trypan blue dye vitality test. Results A reproducible epithelial separation with a smooth surface was achieved in all eyes. The cleavage plane was located between the lamina lucida and the lamina densa. Damage to epithelial cells was mainly limited to the cut margins. Conclusions Mechanical separation of the epithelial sheet in epithelial laser in situ keratomileusis (epi-LASIK) was safe and reproducible with all evaluated microkeratomes. Immunohistochemistry and electron microscopy showed the cleavage plane in epi-LASIK was between the basal epithelium and the basement membrane at the level of the lamina lucida.

The purpose of this study was to characterise an ex-vivo adult porcine retina-retinal pigment epithelium (RPE) perfusion organ culture model. Fresh porcine full-thickness retina-RPE-choroid tissue samples were clamped into tissue carriers and mounted in two-compartment containers. The retinal and choroidal sides were continuously perfused with culture medium. pO(2), [Na(+)], [K(+)], [Cl(-)], [glucose], [lactate], and pH were measured in the medium. Tissue samples were examined after 24h, 4, 7, and 10 days in culture. The morphology of the retina and the RPE was examined by light and electron microscopy (LM, EM). The retinal cellular integrity was further examined by immunohistochemistry (Ki 67, GFAP, rhodopsin, synaptophysin, syntaxin, NF 200, TUNEL-test). Fresh porcine full-thickness retina-RPE-choroid tissue samples and tissue samples in static organ culture served as controls. LM, EM, and immunohistochemistry showed intact retinal and RPE cytoarchitecture kept in perfusion culture. Photoreceptor outer segments showed first signs of degeneration after 24h, significant signs of apoptosis and necrosis appeared in the retina after 4 days in perfusion culture. Control tissue samples kept in static culture showed disintegration of the retinal cytoarchitecture after 4 days in culture. The data show that adult porcine retina-RPE tissue can be maintained morphologically intact in perfusion organ culture for at least 10 days. Although first signs of degeneration set in after 24h the structural preservation of the tissue in perfusion organ culture is superior to that in static culture. The perfusion culture model of the retina refines organotypic in vitro test systems and may help to reduce the number of necessary animal experiments in retina and RPE research. It offers new perspectives for the safety testing of substances designed for intraocular application.

Purpose: Up to date several approaches have been undertaken to achieve an ‘easy-to-handle’ animal model of choroidal neovascularizations (CNVs) in rabbits; however, so far in none of the studies could healthy retinal tissue be maintained, which is mandatory to further investigate the effects of photodynamic therapy (PDT) or anti-vascular-endothelial-growth-factor treatments. It was our aim to reevaluate and verify the method of inducing experimental CNVs in rabbits using subretinally injected linoleic acid hydroperoxide (LHP) as proposed by Tamai et al. and to use it for experimental PDT. Material and Methods: In 33 eyes of Chinchilla breed rabbits LHP of two different concentrations (25 and 100 µg/50 µl) was injected into the subretinal space via a transvitreal approach under guidance of an operation microscope. Ophthalmoscopic and angiographic examinations were performed on days 3, 7, 14 and 28 after surgery. Preliminary PDT with different experimental parameter sets was performed in 3 eyes using the new photosensitizer Tookad. Results: Using LHP in the higher concentration, an angiographically determined CNV induction was observed in 27% of all injection sites (n = 34) on days 14 and 28 revealing early well-demarcated and progressive leakage. No CNV was detected at the lower LHP concentration (60 injection sites). Subretinal CNV was verified histologically revealing vessel formation above the retinal pigment epithelium level. Herein, a significant damage to the outer retinal layers was always observed; however, the general structure of the choriocapillary layer was maintained. Tookad PDT was clinically able to completely stop leakage in 1 case and reduce leakage in 2 cases. Histologically the choriocapillary layer was occluded. Conclusion: Subretinal injection of LHP induces angiographically well-demarcated classic CNVs in rabbits; however, the CNV rate was low, and histology revealed severe damage of the outer retinal layers but not of the choriocapillary layer, which is important for studying PDT interactions. Preliminary experimental PDT could clinically stop or reduce leakage from angiographic CNV. Due to the small CNV rate and the significant collateral retinal tissue damage, this model seems to be only of partial suitability for investigating new treatment modalities in CNV.

To investigate the safety and performance of perfluorohexylethan (O62), a partially fluorinated alkane, as an intraoperative tool and heavy ocular endotamponade in complex vitreoretinal surgery.In a prospective clinical study, O62 was used as a postoperative ocular endotamponade in 11 eyes of 11 patients after pars plana vitrectomy for the following inferior pathologic conditions, proliferative vitreoretinopathy (n = 8), rhegmatogenous retinal redetachment with inferior tears (n = 1), and inferior giant tear (n = 2). The median duration of the O62 tamponade was 43 days (range, 17-55 days), and the median follow-up period after removal of the tamponade was 16 months.The initial postoperative retinal attachment rate was 100%. In 7 of 11 eyes, the retina remained attached during the O62 tamponade and after its removal. During the tamponade period, no epiretinal membrane formation or macular pucker was observed in these seven eyes. Recurrent retinal detachments with proliferative vitreoretinopathy developed in 4 of 11 eyes under the tamponade. The median follow-up after removal of O62 was 16 months. A secondary cataract developed in all five phakic eyes. Severe emulsification was noted in all patients starting in the second week after surgery causing a decrease of visual acuity and a significantly reduced funduscopic view. In the early postoperative period, a marked inflammatory reaction in the anterior segment was seen in all patients. Slightly whitish precipitates were noted in 2 of 11 eyes. A transient increase in intraocular pressure up to 35 mmHg was observed in 2 of 11 eyes.O62 showed good tamponade properties for the inferior retina over 6 weeks. However, its use as a postoperative retinal tamponade is limited by its severe emulsification propensity and unclear inflammatory potential.

Purpose: To study the effects of conventional laser application on the retinal pigment epithelium (RPE) in a perfusion tissue culture model of porcine retinal pigment epithelium without overlying neurosensory retina. Methods: RPE with underlying choroid was prepared from enucleated porcine eyes and fixed in a holding ring (Minusheet®). Specimens were then placed in two-compartment tissue culture containers (MinuCell & Minutissue, Bad Abbach, Germany) and were cultured during continuous perfusion with culture medium at both sides of the entire specimen, the upper RPE and the lower choroid (12 specimens out of 6 eyes). Cultures were kept for 1, 3, 7 and 14 days and were examined histologically. Laser treatment was performed on each tissue ring by application of 3 × 3 laser burns one day after culture began (argon ion laser, wavelength: 514 nm, pulse duration: 100 ms; spot size: 200 µm) using different energy levels (400–1,000 mW); (16 specimens out of 8 eyes). Results: During laser treatment a marked lightening of the RPE with centrifugal spreading was observed. Using higher levels of energy, a contraction of the RPE towards the center of the laser spot was noticed. One day after laser photocoagulation histology revealed destruction of RPE; within 3–7 days of culture, migration and proliferation of neighboring cells was observed in several lesions. After 7 days the initial defect of the irradiated area was covered with dome shaped RPE cells and after 14 days multilayered RPE cells were showing ongoing proliferation. However, there were also cases without proliferation after laser treatment. The non-treated, continuously perfused RPE showed regular appearance in histological sections: during the first 7 days of culture, light microscopy revealed a normal matrix with a well-differentiated RPE monolayer. Subsequently proliferation even without treatment was observed and after 14 days the RPE became multilayered. Conclusion: It was possible to study the early healing response to the effect of laser treatment using the permanently perfused tissue culture system. A marked proliferation and repair of the laser defect could be observed in several but not all lesions. After 14 days even without laser treatment a proliferative multilayered RPE was present. Although this limits the use of the system for longer than 7 days, it seems to be useful for investigation of RPE-related disorders.

Background: To evaluate the ocular toxicity of trypan blue (TB) injected into the vitreous cavity of rabbit eyes. TB is a dye that could be useful for staining epiretinal membranes during vitrectomy surgery. Methods: Ten New Zealand White (NZW) rabbits underwent gas-compression vitrectomy. Rabbits were divided into three groups to receive injections of 0.1 ml basic salt solution, 0.1 ml of a 0.06% TB solution or 0.1 ml of a 0.2% TB solution. Ocular toxicity was assessed by slit-lamp biomicroscopy, ophthalmoscopy, electroretinography and histology. Results: Transient posterior capsule opacification was noted in all animals. No significant reductions in a-wave or b-wave amplitudes were found in any of the animals. Light and electron microscopic examination of the inferior retina in the 0.2% TB-treated eyes showed damaged photoreceptors and marked disorganization. Immunohistochemical staining for rhodopsin was strongly reduced in those sections and staining for proliferation with Ki-67 was positive. No histological abnormalities were found in the upper retina of the 0.2% TB-treated eyes or in any part of the retina of the 0.06% TB-treated or control eyes. No histological abnormalities were found in any of the anterior chamber angle specimens. Conclusions: Although no signs of toxicity were found after the prolonged presence of TB at a concentration of 0.06% in the vitreous cavity of rabbit eyes, marked damage occurred in the lower retina of 0.2% TB-treated eyes. The short-term presence of TB at a concentration of 0.06% in the vitreous cavity is harmless to the rabbit eye but a higher concentration of TB could be unsafe.

Perfluorocarbon liquids (PFCLs) and heavy fluorocarbon liquids (HFCLs) are being increasingly used as soft tools during vitreoretinal surgery. However, since long-term intraocular tolerance is still unsatisfactory, at present complete removal at the end of surgery is recommended. With the aim to improve long-term intraocular compatibility and to enlarge the spectrum of clinical applications, modified HFCLs have been developed. HFCL-oligomers with a higher viscosity represent the latest perspective. All three groups of fluorocarbon liquids will be compared with respect to their physical and chemical properties, experimental and clinical results, and prospects for clinical applications. Common features of PFCLs, HFCLs and HFCL-oligomers are biological inertness, specific gravity higher than water, immiscibility with water or blood, and a high gas binding capacity. In PFCLs such as decalin, octane, or phenanthrene, all carbon atoms of the carbon backbone are completely fluorinated. In experimental and clinical use, emulsification, vascular changes and structural alterations of the retina have been described. By only partial replacement of hydrogen atoms by fluorine, the specific gravity of HFCLs is reduced, whereas lipophilic properties increase. Thus HFCLs are potential solvents for intraocular silicone oil remnants. However, after long-term application, side-effects are similar to those observed with PFCLs. Substances of this group, such as F6H6, F6H8, O44, and O62 are used intraoperatively and are currently being investigated for clinical long-term application. With the aim to avoid emulsification and to improve intraocular tolerance, we have developed HFCL-oligomers consisting of 2–4 HFCL molecules with increased viscosity. The oligomers were tolerated well in rabbit eyes for up to 4 months. In contrast to PFCLs or monomers, they did not emulsify nor show vascular alterations. ERGs returned to normal after removal of the oligomer from the eye. Histology of the retina showed mild alterations. Conclusion: according to physical properties, experimental intraocular compatibility and stability against emulsification, HFCL-oligomers are promising candidates for improved long-term tamponade of the lower retina. At present, indications for an application in human eyes have to be determined in clinical trials.

Background: Partially fluorinated alkanes (FALKs) are a new class of substances which can be used in vitreoretinal surgery as an intraoperative tool and as a long-term tamponade. The aim of this in vitro study was (1) to investigate the solubility of FALKs in silicone oil during direct exchange, (2) to study their combined use and solubility in PFCLs, (3) to evaluate their lipophilic properties and (4) to investigate the possibility of preparing "heavy silicone oil". Methods: (1) Four different FALKs (F6H6, F6H8, O44 and O62) were directly exchanged with silicone oil (5,000 mPas). The dissolved amount of fluorocarbons in the removed silicone oil was determined by gas chromatography and by gravimetry. Furthermore, the diffusion phenomena during the exchange process were studied. (2) The behaviour of FALKs in PFCLs was investigated and the solubility of the resulting mixtures in silicone oil was measured. (3) The solubility of FALKs and PFCLs in native olive oil was analysed. (4) Different FALKs were added to silicone oil and measurements of the resulting specific gravity and the viscosity were performed. Results: (1) FALKs dissolved in silicone oil up to the following values: F6H6=45 m%, F6H8=54 m%, O44=100 m%, O62=18 m%. (2) FALKs dissolved in PFCL, thereby changing the physicochemical properties of PFCL depending on the type of FALK and ratio used. (3) The lipophilic properties of FALKs and PFCLs could be characterized by their dissolution in native olive oil (F6H8=23.4 m%, O44=16.7 m%, F6H6=12.3 m%, O62=5.3 m%, PFD=1.1 m%, PFO=0.6 m%). (4) It was possible to prepare "heavy silicone oil" e.g. by adding 30 vol% F6H8, resulting in a specific gravity of 1.08 g/ml, or by adding 80 vol% O44, resulting in a specific gravity of 1.25 g/ml, but decreasing the viscosity of the mixtures dramatically. Conclusion: (1) If FALKs are used as an intraoperative tool, a direct exchange with silicone oil should be avoided owing to their capacity to dissolve in silicone oil, resulting in a mixture with unpredictable properties. (2) A combined use with PFCLs and silicone oil is possible, if the right ratio is chosen. (3) The solubility of FALKs in native olive oil may be an indicator for their tissue penetration and may render feasible their use as a long-term tamponade. (3) "Heavy silicone oil" preparation using FALKs is possible, but the mixture needs further evaluation in terms of emulsification, mobilization of oligosiloxanes, tissue penetration and long-term stability.

Es wird eine Ubersicht uber den Stand der Entwicklungen eines subretinalen, elektronischen Mikrophotodioden-Arrays gegeben, mit dem degenerierte Photorezeptoren ersetzt werden konnen. Verschiedene Prototypen wurden entwickelt, getestet und bei verschiedenen Versuchstieren bis zur Dauer von 18 Monaten implantiert. Die Tatsache, dass mit subretinalen Elektroden elektrische Antworten vom visuellen Kortex von Schweinen abgeleitet werden konnen und Antworten auch in vitro in Netzhauten von Ratten mit Netzhautdegenerationen nachweisbar sind, zeigt die Sinnhaftigkeit dieses Ansatzes. Allerdings sind noch wichtige Fragen der Biokompatibilitat, der Langzeitstabilitat und der Art des vermittelbaren Bildeindrucks zu bearbeiten, bevor an einen Einsatz beim Menschen zu denken ist.

Micro-photodiode arrays based on semiconductor chip technology are being developed to replace degenerated photoreceptor cells in the retina. Electric current is generated in tiny micro-photodiodes and delivered to the adjacent tissue by micro-electrodes. One of the main requirements of a sub-retinal implantable device is long-term stability versus corrosion in vivo (biostability). Biostability of micro-photodiode arrays (MPDA) was investigated in vitro and in vivo. No significant damage was found on chips immersed for up to 21 months in saline solution. Under in vivo conditions, however, the silicon oxide passivation layer of the chip was dissolved within a period of about 6-12 months. Subsequently, the underlying silicon was corroded. In contrast, stimulation electrodes consisting of titanium nitride were well preserved both in vitro and in vivo. The deterioration of the electrical properties of the micro-photodiodes correlated with the morphological damage observed. Strategies aiming at the development of an improved biostable encapsulation of neurotechnological implants have to be investigated and will be discussed briefly.