Gernot Roessler

Implantation and Explantation of a Wireless Epiretinal Retina Implant Device: Observations during the EPIRET3 Prospective Clinical Trial

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.

Accuracy of intraocular lens power calculation using partial coherence interferometry in patients with high myopia.

Citation information: Roessler GF, Dietlein TS, Plange N, Roepke A‐K, Dinslage S, Walter P, Mazinani BAE. Accuracy of intraocular lens power calculation using partial coherence interferometry in patients with high myopia. Ophthalmic Physiol Opt 2012, 32, 228–233. doi: 10.1111/j.1475‐1313.2012.00903.x

Implantation of a Novel Telemetric Intraocular Pressure Sensor in Patients With Glaucoma (ARGOS Study): 1-Year Results

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.).

Towards the bionic eye — the retina implant: surgical, opthalmological and histopathological perspectives

Degenerations of the outer retina such as retinitis pigmentosa (RP) lead to blindness due to photoreceptor loss. There is a secondary loss of inner retinal cells but significant numbers of bipolar and ganglion cells remain intact for many years. Currently, no therapeutic option to restore vision in these blind subjects is available. Short-term pattern electrical stimulation of the retina using implanted electrode arrays in subjects blind from RP showed that ambulatory vision and limited character recognition are possible. To produce artificial vision by electrical retinal stimulation, a wireless intraocular visual prosthesis was developed. Images of the environment, taken by a camera are pre-processed by an external visual encoder. The stimulus patterns are transmitted to the implanted device wirelessly and electrical impulses are released by microcontact electrodes onto the retinal surface. Towards a human application, the biocompatibility of the utilised materials and the feasibility of the surgical implantation procedure were stated. In acute stimulation tests, thresholds were determined and proved to be within a safe range. The local and retinotopic activation of the visual cortex measured by optical imaging of intrinsic signals was demonstrated upon electrical retinal stimulation with a completely wireless and remotely controlled retinal implant. Potential obstacles are reviewed and further steps towards a successful prosthesis development are discussed.

Does surgical experience have an effect on the success of retinal detachment surgery

Purpose: To examine the relationship between surgeon experience and success rates in retinal detachment surgery. Methods: Success rates during a follow-up of 11 months of 8 surgeons who performed in total 375 retinal detachment procedures ranging from 14 to 115 cases between December 1997 and January 2002 were correlated to the total number of vitreoretinal procedures ranging between 176 and 2,587. All patients received either scleral buckling or vitrectomy, and complicated cases were excluded. Results: Mean primary anatomical success rates were 0.69 ± 0.14 for scleral buckling and 0.9 ± 0.05 for primary vitrectomy (P < 0.05). The primary anatomical success rates did not correlate to the number of vitreoretinal procedures. Seven of the eight surgeons showed an intraindividual learning effect with better success rates in the second versus the first half of the observed procedures. The learning effect was correlated to the total number of procedures with a higher effect in inexperienced surgeons. Conclusion: An intraindividual learning effect that was higher in inexperienced surgeons could be demonstrated. The learning effect was reduced by half after 500 vitreoretinal procedures while the primary anatomical success rates were not correlated to the number of vitreoretinal procedures.

Ocular Pulse Amplitude Before and After Cataract Surgery

Purpose: To investigate the impact of cataract surgery on the association of the ocular pulse amplitude (OPA) and intraocular pressure (IOP) with respect to the interpretation of OPA as an estimate of ocular blood flow. Methods: Twenty-four patients with cataract were included in a clinical study. OPA was measured using dynamic contour tonometry (DCT, Pascal®, SMT Swiss Microtechnology AG, Switzerland). IOP was measured by means of Goldmann applanation tonometry (IOP GAT) and DCT (IOP DCT). All measurements were performed before and one day after cataract surgery. Results: At baseline, OPA was correlated to IOP GAT (r = 0.67, P = 0.0002) and IOP DCT (r = 0.82, P < 0.0001), but not to age or axial length. Postoperative OPA was correlated to IOP GAT (r = 0.67, P = 0.0002) and IOP DCT (r = 0.65, P = 0.0004). In 17 patients, IOP GAT decreased after surgery (IOP DCT n = 14), whereas an increase was apparent in seven patients (IOP DCT n = 10). The mean absolute deviation of IOP GAT pre- to post-surgery was 4.54 mmHg ± 2.47 (range 1–10 mmHg) and 5.4 mmHg ± 3.2 (range 1.1–13.1 mmHg) for IOP DCT. The changes of OPA were significantly correlated to changes in IOP GAT (r = 0.48, P = 0.017) and IOP DCT (r = 0.60, P = 0.001). IOP GAT and IOP DCT changes were not correlated to changes in corneal thickness. Conclusions: The OPA measured with the Pascal® device seems to be dependent on IOP changes. Particular caution should be taken in the interpretation of OPA in estimating pulsatile ocular blood flow.

Accuracy and reproducibility of axial length measurement in eyes with silicone oil endotamponade

Aim: To assess the accuracy and signal quality of axial length measurements by partial coherence laser interferometry (PCI) for optical biometry in eyes with conventional silicone oil (SO) or heavy silicone oil (HSO) as endotamponade. Methods: We included 26 eyes with SO endotamponade (SO, n = 15; HSO, n = 11) using a Zeiss IOLMaster for measurement of axial length the day before and at least 6 weeks after SO removal. We analysed the intra-individual deviation between both measurements and signal-to-noise ratio (SNR) as a marker for signal quality. We included 16 contralateral eyes without history of vitreoretinal surgery to act as the control group. Results: The mean axial length was 24.76 (SD 2.07) mm (SO 24.63 (SD 2.12) mm, HSO 24.93 (SD 2.10) mm, control 24.95 (SD 2.61) mm) before and 24.75 (SD 1.96) mm after oil removal with a mean intra-individual deviation of 0.13 (SD 0.11) mm (SO 0.13 (SD 0.12) mm, HSO 0.13 (SD 0.09) mm, control 0.02 (SD 0.01) mm) while SNR at baseline was 5.7 (SD 3.5) (SO 6.6 (SD 4.0), HSO 4.4 (SD 2.2), control 8.6 (SD 3.9)). Conclusion: In our analysis, optical biometry using PCI generated results with acceptable accuracy and signal quality for measurement of axial length in SO-filled eyes.

Improving the quality of multifocal visual evoked potential results by calculating multiple virtual channels.

PurposeTo introduce a method for improvement of multifocal VEP (mfVEP) recordings by prediction of waveforms at multiple positions on the surface of the skull.MethodsFifteen healthy participants (mean age 24 ± 3.8 years) underwent mfVEP recordings from 3 surface positions. Two methods of a best-of-mfVEP approach were used and compared. In the first, a standard procedure, further data from 3 calculated channels were used. In the second approach, mfVEPs were obtained by using data derived from 40 virtual electrode positions on the basis of predictions from dipole source calculations.ResultsThe mean signal-to-noise ratios (SNRs) of the best-of-mfVEPs of both methods were compared. The SNR was significantly higher for mfVEP data using additional virtual recordings revealed by dipole source determination (2.87 vs. 3.36; P < 0.035).ConclusionWe conclude that multichannel prediction of mfVEP responses based on dipole source calculation significantly improves the quality of the examination results compared with the currently prevalent standard method.

Clinical Observations and Occurrence of Complications following Heavy Silicone Oil Surgery

Purpose. To demonstrate development and complications in heavy silicone oil (HSO) surgery in 100 eyes following primary vitreoretinal surgery. Methods. 100 eyes were included in this retrospective study that underwent vitreoretinal surgery using HSO as endotamponade. Indication diagnoses were retinal detachments (n = 76), complicated macular holes (MH) (n = 20), and others (n = 4). HSO removal was performed after a mean period of 20.2 ± 19.0 weeks. In 18 eyes with poor functional prognosis the silicone oil remained permanently for stabilisation. Overall follow-up time was 35.9 ± 51.8 weeks. Results. The mean IOP before HSO surgery was 13.3 ± 5.6 mmHg and raised to an average maximum of 23.3 ± 8.5 mmHg postoperatively and decreased to 13.7 ± 7.2 mmHg after removal. Secondary IOP raise due to emulsification of the silicone oil endotamponade was seen in 29 eyes after 7.8 ± 4.5 weeks. Other complications being observed with HSO installed were persistent corneal erosion (n = 3) and prolonged anterior chamber inflammation (n = 29). In 13 eyes recurrent retinal detachments occurred during followup. Conclusions. According to our analysis HSO surgery might deliver satisfying results in complicated cases of ophthalmological surgery. However, potential complications should always be taken into account when making the decision if to use and when to remove HSO in complicated retinal surgery.

Retrobulbar blood flow and visual field alterations after acute ethanol ingestion.

Background The purpose of this study was to test the effect of ethyl alcohol on the koniocellular and magnocellular pathway of visual function and to investigate the relationship between such visual field changes and retrobulbar blood flow in healthy subjects. Methods In 12 healthy subjects (mean age 32 ± 4 years), color Doppler imaging, short-wavelength automated perimetry, and frequency doubling perimetry was performed before and 60 minutes after oral intake of 80 mL of 40 vol% ethanol. Mean and pattern standard deviations for short-wavelength automated and frequency doubling perimetry were assessed. End diastolic velocity (EDV) and peak systolic velocity (PSV) were measured in the central retinal and ophthalmic arteries using color Doppler imaging. Systemic blood pressure, heart rate, intraocular pressure, and blood alcohol concentration were determined. Results Mean PSV and EDV in the central retinal artery showed a significant increase after alcohol intake (P = 0.03 and P = 0.02, respectively). Similarly, we found a significant acceleration of blood flow velocity in the ophthalmic artery (P = 0.02 for PSV; P = 0.04 for EDV). Mean intraocular pressure decreased by 1.0 mmHg after alcohol ingestion (P = 0.01). Retinal sensitivity in short-wavelength automated perimetry did not alter, whereas in frequency doubling perimetry, the mean deviation decreased significantly. Systolic and diastolic blood pressure did not change significantly. Mean blood alcohol concentration was 0.38 ± 0.16 g/L. Conclusion Although ethanol is known to cause peripheral vasodilation, our subjects had no significant drop in systemic blood pressure. However, a significant increase of blood flow velocity was seen in the retrobulbar vessels. Regarding visual function, moderate alcohol consumption led to reduced performance in the magnocellular visual system tested by frequency doubling perimetry, but had no effect on short-wavelength automated perimetry.