Publications (9)16.17 Total impact
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Article: Acute electrical stimulation of the human retina with an epiretinal electrode array.
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ABSTRACT: To determine the threshold charges needed for eliciting visual perceptions through acute electrical stimulation of the human retina in patients suffering from retinitis pigmentosa, using an epiretinal microelectrode array. In a multicentre study, 20 patients (average age 55 years) with visual acuities ranging from 4/200 to no light perception were included. The stimulation procedure was performed during a pars plana vitrectomy, for a maximum of 45 min, by using a microcontact film with IrO(x) electrodes connected by cable to a current generator. After repeated stimulation and threshold charge determination, the microelectrode array was removed. Nineteen of 20 patients stated in the postoperative interviews that they experienced one or more visual perceptions with close time correlation to single stimulation events. Minimum threshold charges needed to generate visual perceptions could be measured and verified in 15 patients. The charge level ranged from 20 to 768 nC with single or multiple electrodes. One patient suffered a retinal detachment during the procedure; this patient's retina was successfully reattached. There were no further adverse reactions observed during the 3-month follow-up. Acute epiretinal stimulation of the human retina, using a microelectrode array, can elicit visual perceptions in blind patients with retinitis pigmentosa.Acta ophthalmologica 11/2011; 90(1):e1-8. · 2.44 Impact Factor -
Article: Radial optic neurotomy in central retinal vein occlusion does not influence ocular hemodynamics.
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ABSTRACT: radial optic neurotomy (RON) is used for the treatment of central retinal vein occlusion. Its effects on visual acuity differ substantially between patients. Our study aims to evaluate if RON has an impact on ocular microcirculation and if analysis of ocular microcirculation might serve as a predictor for surgical success. a complete ophthalmologic examination including color Doppler imaging of the retrobulbar vessels was performed before and 2-4 months after RON in 12 patients. mean visual acuity was 0.09 ± 0.03 prior to and 0.24 ± 0.12 after RON. Visual acuity improved in 7 (+3.5 ± 0.9 lines), was stable in 3 (± 0 lines) and worsened in 2 cases (-6 and -2 lines). Doppler parameters were not affected by RON, and no correlations between visual acuity and perfusion parameters were found. Conclusions: Our data indicate that RON does not influence ocular microcirculation. None of the assessed hemodynamic parameters appears to be a predictor for surgical success.Ophthalmologica 01/2011; 225(1):41-6. · 1.42 Impact Factor -
Article: Correlation of nonsense and frameshift mutations with severity of retinal abnormalities in neurofibromatosis 2.
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ABSTRACT: Neurofibromatosis 2 (NF2) is an autosomal dominant disease that is characterized by nervous system tumors and ocular abnormalities. To investigate genotype-phenotype correlations demonstrated for NF2-associated nervous system tumors, cataracts, and retinal lesions. Forty-eight patients with NF2 from a tertiary neurological referral center underwent screening for constitutional NF2 mutations with multiple screening methods. Each patient underwent a complete ophthalmic examination, including fluorescein angiography to detect retinal vascular lesions. Retinal abnormalities (epiretinal membranes or retinal microaneurysms) were present in 25 of the 48 patients (52%). The occurrence of epiretinal membranes and retinal microaneurysms was highly correlated, but retinal abnormalities were not significantly correlated with cataracts (present in 39 of 47 patients [83%]). Logistic regression with full constitutional nonsense or frameshift mutations as the reference group demonstrated that somatic mosaicism was associated with a significantly lower likelihood of retinal abnormalities (odds ratio, 0.05; 95% confidence interval, 0.01-0.49). To our knowledge, this is the first genetic, clinical, and angiographic characterization of retinal abnormalities in NF2. Severe mutations are correlated with a more severe retinal involvement. Clinical Relevance Retinal abnormalities, which can be revealed by means of fluorescein angiography, are more common in patients with NF2 who have nonsense or frameshift mutations.Archives of ophthalmology 11/2008; 126(10):1376-80. · 3.86 Impact Factor -
Article: Neurofibromatosis 2 leads to higher incidence of strabismological and neuro-ophthalmological disorders.
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ABSTRACT: Ophthalmic features of neurofibromatosis 2 (NF2) include juvenile cataract, retinal hamartomas and tumours of the cranial nerves. We hypothesize that these tumours lead to strabismological and neuro-ophthalmological symptoms, including palsies of cranial nerves III, IV and VI, nystagmus and gaze palsies. We carried out a retrospective review of 73 patients with known genotype. They underwent ophthalmic, neuro-ophthalmological and strabismological examination. Statistical analysis was performed by calculating odds ratios and their 95% confidence intervals. Mean best corrected visual acuity was 0.85. Strabismus was found in 38 of 73 patients (52%). A deviation based on a cranial nerve palsy was found in 16 patients (22%) and three had supranuclear palsies. Eleven of 73 patients had a nystagmus, mostly caused by peripheral-vestibular disturbance. Binocular single vision was normal in 41 (58%), subnormal in six (8%) and not present in 24 (34%) patients. The average refractive error was - 0.57 D. Myopia of >or= 0.5 D was present in 47 (33%) eyes and hyperopia of >or= 2.0 D was measured in 11 (8%) eyes. In the subgroup analysis of NF2 mutation types, the relative risk for cranial nerve palsies and negative stereopsis was statistically significantly increased for the nonsense mutation group. The mosaicism group had a statistically significant decreased relative risk for concomitant squint, as did patients with unfound mutations for strabismus and poor stereopsis. The present study is, to our knowledge, the first to examine a larger collection of NF2 patients for strabismological and neuro-ophthalmological lesions. Compared with the normal population, our sample showed a higher amount of strabismus, refractive errors and an increased incidence of vestibular nystagmus.Acta ophthalmologica 10/2008; 86(8):882-6. · 2.44 Impact Factor -
Chapter: The IMI Retinal Implant System
09/2007: pages 111-128; -
Article: Neurofibromatosis 2 leads to choroidal hyperfluorescence in fluorescein angiography.
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ABSTRACT: For the diagnosis of NF 2, ocular findings like juvenile cataract, retinal and combined hamartomas of the retinal pigment epithelium and the retina as well as tumours of the optic nerve play an important role. An early diagnosis is essential in order to inhibit deafness from bilateral vestibular schwannoma. But sometimes the Manchester diagnostic criteria for NF2 are not completely fulfilled. Frequently, suspicious macular anatomy is found in neurofibromatosis 2 (NF2) patients. We hypothesise that the underlying retinal pigment epithelium or the retina of the macular region alters in NF2 patients. Therefore, we have tested by fluorescence angiography whether NF2 is associated with chorioretinal changes. In a prospective study, 48 patients matching the criteria for NF2 with known genotype underwent a complete ophthalmic examination including funduscopy and fluorescence angiography. The influence of the genotype was statistically analysed by odds ratios and their 95% confidence intervals. Eleven eyes of nine patients showed choroidal hyperfluorescence in the macular region on fluorescence angiography. There was staining spreading from grainy hyperfluorescence to minor variants of a combined hamartoma of the retina and the retinal pigment epithelium. All of these manifestations presented without leakage in the late angiographic phases. These choroidal findings were present in one patient with frameshift mutation, in two patients with nonsense mutations and in six patients with splice site mutations of the NF2 gene. The statistical analysis showed a significant lower risk of choroidal alterations in patients with somatic mosaicism, deletions and unfound mutations. Using fluorescence angiography pathological changes of the macular region can be detected in NF2 patients. The ophthalmic examination, which often is limited to the anterior eye segment, may play a role in finding the diagnosis in incomplete NIH criteria. The presented study shows chorioretinal hyperfluorecences without leakage of the macular region, which might be considered as a forme fruste of a hamartoma. Choroidal hyperfluorescences add to the spectrum of genotype-phenotype correlations in NF2.Albrecht von Graæes Archiv für Ophthalmologie 08/2007; 245(7):949-53. · 2.17 Impact Factor -
Article: A method and technical equipment for an acute human trial to evaluate retinal implant technology.
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ABSTRACT: This paper reports on methods and technical equipment to investigate the epiretinal stimulation of the retina in blind human subjects in acute trials. Current is applied to the retina through a thin, flexible microcontact film (microelectrode array) with electrode diameters ranging from 50 to 360 microm. The film is mounted in a custom-designed surgical tool that is hand-held by the surgeon during stimulation. The eventual goal of the work is the development of a chronically implantable retinal prosthesis to restore a useful level of vision to patients who are blind with outer retinal degenerations, specifically retinitis pigmentosa and macular degeneration.Journal of Neural Engineering 04/2005; 2(1):S129-34. · 3.84 Impact Factor -
Article: New Laser Treatment Options in Age-related Macular Degeneration: Transpupillary Thermotherapy
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ABSTRACT: Age-related macular degeneration (ARMD) is the leading cause of legal blindness in the developed countries (22, 24). The deterioration of central visual acuity, the development of metamorphopsia and a central scotoma lead to a reduction of patients' reading capacities, which can extend to a threatening degree even in early stages. A consequence of this loss of vision can be social dependence, demonstrating the enormous social importance of ARMD (19). Depending on the clinical presentation, two different main forms may be distinguished: a dry and a wet form (63). The first one is characterized by an accumulation of debris in the different layers of the retinal pigment epithelium, called drusen, which may be miliar, serous or confluent, basic laminar or linear, finally leading to a rarefaction of the retinal pigment epithelium, in form of areolar or geographic atrophy.The genesis of the disease is considered to be multifactorial, genetic factors interfering with regulatory functions of the retinal pigment epithelium seem to be involved (64).By lesions of Bruch's membrane or the pigment epithelium, choroidal neovascularizations (CNV) may sprout underneath the retinal pigment epithelium or the sensory retina (4, 5, 6, 46). Two different angiographic features must be distinguished: a classic form with a well demarked border of the CNV and an occult form, which shows late leakage from hyperfluorescent lesions, detachment of the retinal pigment epithelium with notches or “pin points”. This may lead to extravasation of liquid, to intra- and subretinal hemorrhage and, in the end, to a fibrotic destruction of the retina, resulting in a scar. Characteristically, these CNV are localized directly under the macula, particularly under the foveal avascular zone (21, 55). Thus, therapeutic options like laser coagulation and surgical interventions are limited. Furthermore, the surgical interventions like CNV excision, macular translocation or transplantation of the retinal pigment epithelium are still at an experimental stage (52).Apart photodynamic therapy, which uses a photosensitizing agens, transpupillary thermotherapy is a new and noninvasive method to treat choroidal neovascularization. Based on a low grade hyperthermia, mostly sparing the surrounding tissue, laser light derived from an infrared diode laser at 810 nm is used to apply long pulse spots of 60 seconds of duration. Energy is chosen depending on the spot size 509 mW (spot: 2000 μm) and 800 mW (spot: 3000 μm), respectively.At the time of diagnosis, 8% of the patients suffer from bilateral disease. If the degeneration is unilateral, the risk for the fellow eye amounts to 10–12% per year (4, 13, 23).Medical Laser Application. -
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2005–2008
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Universität Hamburg
- Department of Ophthalmology
Hamburg, Hamburg, Germany
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