Purpose. Visual sensations in patients with blindness and retinal degenerations may be restored by electrical stimulation of retinal neurons with implantable microelectrode arrays. A prospective trial was initiated to evaluate the safety and efficacy of a wireless intraocular retinal implant (EPIRET3) in six volunteers with blindness and RP. methods. The implant is a remotely controlled, fully intraocular wireless device consisting of a receiver and a stimulator module. The stimulator is placed on the retinal surface. Data and energy are transmitted via an inductive link from outside the eye to the implant. Surgery included removal of the lens, vitrectomy, and implantation of the EPIRET3 device through a corneal incision. The clinical outcome after implantation and explantation of the device was determined. The implant was removed after 4 weeks, according to the study protocol. results. Implantation was successful in all six patients. While the anterior part was fixed with transscleral sutures, the stimulating foil was placed onto the posterior pole and fixed with retinal tacks. The implant was well tolerated, causing temporary moderate postoperative inflammation, whereas the position of the implant remained stable until surgical removal. In all cases explantation of the device was performed successfully. Adverse events were a sterile hypopyon effectively treated with steroids and antibiotics in one case and a retinal break in a second case during explantation requiring silicone oil surgery. conclusions. The EPIRET3 system can be successfully implanted and explanted in patients with blindness and RP. The surgical steps are feasible, and the postoperative follow-up disclosed an acceptable range of adverse events.

Purpose. To demonstrate local cortical activations in the primary visual cortex of the cat as a result of retinal electrical stimulation by means of a completely wireless-controlled, implantable retinal prosthesis in a series of acute experiments. methods. The transfer of energy to drive the device and signals to activate any combination of 25 retinal electrodes was achieved completely wirelessly by an external transmitter positioned in front of the eye. Individually configured electrical stimuli were applied via any combination of 25 electrodes, on sending the necessary pulse parameters to the implant. Placement of the implant onto the retinal surface was achieved after lensectomy and vitrectomy in the cat. Fixation was performed with a retinal tack. Cortical activation patterns were recorded by means of optical imaging of intrinsic signals. results. Implantation and fixation were successfully performed in three cats. Wireless activation of the implant by radiofrequency was demonstrated by recording of stimulus artifacts from the sclera. Local activation of the visual cortex measured by optical imaging of intrinsic signals revealed a shift of cortical response that was well correlated with a change in the position of the activated retinal electrodes. conclusions. The results demonstrate the retinotopic activation of the visual cortex using a completely wireless, remote-controlled retinal implant.

Purpose.: We investigated the safety of a telemetric IOP sensor and the accuracy of its IOP measurements in six patients with open-angle glaucoma and cataract. Methods.: The study design was a prospective, single-center clinical trial. Here we present 1-year follow-up data. A ring-shaped telemetric IOP sensor was implanted in the ciliary sulcus after implantation of the intracapsular lens, during planned cataract surgery. The sensor is encapsulated in silicone rubber and consists of a miniature device with eight pressure-sensitive capacitors and a circular microcoil antenna. IOP measurements are performed with a reader unit held in front of the eye. IOP is calculated as the differences between the absolute pressure inside the eye (pressure sensor) and that outside the eye (reader unit). Results.: The sensor was successfully implanted in all patients. Four patients developed sterile anterior chamber inflammation that resolved completely within 9 days after surgery with anti-inflammatory treatment. All patients showed mild to moderate pupillary distortion and pigment dispersion after surgery. Telemetric IOP measurement was performed in all patients at all visits, and the patients successfully performed self-tonometry at home after receiving instructions. Telemetric IOP values showed similar profiles compared to those of Goldmann applanation tonometry (GAT). Three patients showed a relevant IOP step during follow-up, and in one patient, negative values were obtained throughout the study. Conclusions.: Despite early postoperative anterior chamber inflammation, the IOP sensor was well tolerated by all patients. We describe the first prospective clinical study of a noncontact IOP sensor that potentially enables continuous IOP monitoring in patients with glaucoma. The sensor shape and size needs to be adapted to avoid pupillary distortion and to confirm that IOP measurements are accurately recorded in comparison to those of GAT. ( www.germanctr.de; number DRKS00003335.)

Background: Corneal endothelial dysfunction remains the most frequent indication for corneal transplantation, limited by donor material shortage, poor long-term graft survival, or allogeneic graft rejection. Therefore, tissue-engineered endothelial grafts (TEEG) represent a promising alternative to human donor tissue. In this study, we generated electro-spun scaffolds and tested these for their suitability for human corneal endothelial cell (hCEC) cultivation. Methods: The polymers poly(methyl-methacrylate) (PMMA), poly(lactic-co-glycolic acid) (PLGA), and polycaprolactone (PCL) were spun with equal parameters. HCEC-12 was cultured on the scaffolds for 3 to 7 days. Scaffolds were evaluated by light microscopy, porometry, light transmission, scanning electron microscopy (SEM), live/dead staining and cell viability assay. Results: Electro-spun fibers from PMMA (2.99 ± 0.24 µm) showed significantly higher diameters than PCL (2.29 ± 0.11 µm; p = 0.003) and PLGA (1.84 ± 0.21 µm; p < 0.001), while fibers from PCL also showed larger diameters than those from PLGA (p = 0.002). PMMA scaffolds (26.77 ± 17.48 µm) had significantly larger interstitial spaces than those from PCL (13.30 ± 5.47 µm; p = 0.04) and PLGA (10.42 ± 6.15 µm; p = 0.002), while PCL and PLGA did not differ significantly (p = 0.26). SEM analysis revealed that only PLGA fibers preserved a normal HCEC-12 morphology. PLGA and PCL did not differ in cell number, death, or viability after 7 days of HCEC-12 cultivation. PMMA showed significantly higher cytotoxicity (p < 0.001; PLGA: 1626.2 ± 183.8 RLU; PMMA: 841.9 ± 92.7 RLU; PCL: 1580.2 ± 171.02 RLU). Conclusions: The biodegradable PLGA and PCL electro-spun scaffolds resulted in equal biocompatibility, while PMMA showed cytotoxicity. Only PLGA preserved hCEC morphology and consequently seems to be a promising candidate for TEEG construction.

In the widely used mouse model of retinal degeneration, rd1, the loss of photoreceptors leads to rhythmic electrical activity of around 10–16 Hz in the remaining retinal network. Recent studies suggest that this oscillation is formed within the electrically coupled network of AII amacrine cells and ON-bipolar cells. A second mouse model, rd10, displays a delayed onset and slower progression of degeneration, making this mouse strain a better model for human retinitis pigmentosa. In rd10, oscillations occur at a frequency of 3–7 Hz, raising the question whether oscillations have the same origin in the two mouse models. As rd10 is increasingly being used as a model to develop experimental therapies, it is important to understand the mechanisms underlying the spontaneous rhythmic activity. To study the properties of oscillations in rd10 retina we combined multi electrode recordings with pharmacological manipulation of the retinal network. Oscillations were abolished by blockers for ionotropic glutamate receptors and gap junctions. Frequency and amplitude of oscillations were modulated strongly by blockers of inhibitory receptors and to a lesser extent by blockers of HCN channels. In summary, although we found certain differences in the pharmacological modulation of rhythmic activity in rd10 compared to rd1, the overall pattern looked similar. This suggests that the generation of rhythmic activity may underlie similar mechanisms in rd1 and rd10 retina.