[Primary and secondary prophylaxis of AMD by antioxidants: current risk-benefit data]. / Primäre und sekundäre Prophylaxe der AMD durch Antioxidantien: Aktuelle Datenlage zu Nutzen und Risiken.

Supplementation of antioxidants is widely used in industrialized countries. Their popularity is based on the idea that antioxidants may avoid harmful effects caused by reactive oxygen species and in this way provide a primary and/or secondary prophylaxis against age-related diseases. AREDS was the first study that could prove a secondary prophylactic effect of antioxidants and zinc in patients with AMD. The published recommendations of the AREDS study and their transfer into practical ophthalmological care need a critical review. On the background of the original AREDS data it seems that the recommendation for supplementation includes too many AMD patients. The risks and potential side effect of the AREDS medication should always be critically considered. Currently available data do not provide evidence for an effective primary prophylaxis of AMD by the supplementation of antioxidants. Data on a positive effects of vitamin E supplementation are insignificant, but can be characterized as borderline. A paradigmatic change seems to develop in the present scientific discussion concerning the use of antioxidants, especially on the background of data from extensive meta-analyses which seem to indicate an increase of mortality risks in patients with antioxidant supplementation.

[Development of a minimally invasive retinal implant system]. / Entwicklung eines minimal-invasiven Retinaimplantats.

PURPOSE: It was the aim of this project to develop a minimally invasive prosthetic retinal implant system for the rehabilitation of blind patients suffering from distal retinal degenerations. For this purpose, encoded image information will be transferred to surviving retinal neurons by electrical stimulation applied via intraretinal microelectrodes. METHODS: The technological concept was generated in a feasibility study of alternative approaches to minimally invasive retinal prostheses. Then two series of test implants were fabricated and applied in different in vitro- and in vivo- studies before a long-term implantation trial was initiated. RESULTS: The conceptual design process was resulting in a system with stimulating microelectrodes penetrating the sclera and choroid ab externo, and with all other implant components in episcleral position. Microelectrode penetration and surgical application techniques were successfully tested in several series of experiments. Finally, a long-term application of test devices was successfully initiated. CONCLUSION: Results so far demonstrate the conceptual feasibility, easy-to-perform surgical application, and long-term biocompatibility of the newly designed minimally invasive retinal implant system.

A new approach towards a minimal invasive retina implant.

The possibility of using retina implants ('retinal prostheses') for the restoration of basic orientation in blind patients suffering from distal retinal diseases is presently under investigation by at least 18 independent project groups worldwide. It is a common feature of all implants to bypass degenerated retinal layers and to transfer visual information into the retinal network either by direct electrical stimulation or by neurotransmitter release. Contemporary implant designs are differing in the position of stimulating electrodes (epiretinal, subretinal, external) and the anatomical arrangement of implant components (intraocular, extraocular). The latter is of high relevance with regard to possible implant-tissue interactions and biological reactions. During the last few years new types of implants appeared that reduce intraocular components which are now deposited on the outer scleral surface or even in extraorbital position. The extreme of this trend are completely extraocular implants with transchoroidal or extraocular stimulation of the retina. The new type of implant presented in this paper combines the principle of direct retinal stimulation and minimal invasive implantation in a way that stimulating electrodes are the only implant component penetrating the eye via sclera, choroid and retinal pigment epithelium. All other device elements are positioned in extraocular position. The new concept necessitates a paradigmatic change about surgical handling of the choroid and multiple penetrations of the eye. Successful data about this type of retinal prosthesis are already available from long-term observation in non-human primates.

Experimental implantation of epiretinal retina implants (EPI-RET) with an IOL-type receiver unit.

The purpose of this paper is to investigate the surgical feasibility of implantation and long-term structural outcome of retina implant devices with an anterior IOL receiver, a connecting microcable and posterior segment epiretinal microcontacts. Implantation of epiretinal retina (EPI-RET) implants was performed as a one-step surgical procedure including phacoemulsification and pars plana vitrectomy in two adult rabbits. Implants were mechanically stabilized in an anterior position by the lens capsule and in the posterior segment by microtacks with a soft contact collar. Follow-up (6 and 9 months) included regular clinical examination, anterior and posterior segment photography and finally pathohistological evaluation. Implantation was uneventful in case 1 and complicated by vitreous space haemorrhage in case 2. At the end of follow-up, the retina was partially detached in animal 1 and subtotally detached in animal 2. Common features of tissue reaction in both cases were the formation of cyclitic membranes extending around and posterior to the anterior IOL receiver. In addition to that severe proliferations developed around microcables, microcontacts and microtacks forming a tissue capsule around posterior segment foreign materials. Retinal areas in contact to implant devices presented a severe structural damage and disorganization. Results of this preliminary trial suggest that the application of epiretinal prostheses with large diameter IOL receivers may be a critical issue and can give rise to an unfavourable outcome. Further systematic investigation ought to be performed involving a larger number of animals, modified implants and perhaps other species.

[Electrical stimulation of the visual system. From empirical approach to visual prostheses]. / Elektrostimulation des visuellen Systems. Von therapeutischer Empirie zur Entwicklung von Sehprothesen.

The investigation of the influence of electrical stimulation on the visual system can be sub-divided into empirical, diagnostic and therapeutic phases of development. The first electrical stimulations of the visual system in animals dating back to the eighteenth century represent empirical approaches well before knowledge on the principles of bioelectrical nerve activity was available. Despite this lack of understanding, attempts were made at that time to treat blind people by electrical stimulation. More than 100 years later, with the advancement of technology and knowledge on nerve function, attempts were made to establish various methods of electrical stimulation for the diagnosis of different diseases of the visual system. For more than 30 years attempts to develop electrical devices have been made to by-pass defects of the visual system and to restore basic orientation. Presently nine different groups world-wide are focusing on retinal, optic or cortical implants. A short review on the historical use of electrical stimulation and new therapeutical attempts are given in this paper.

Original papers: Ocular motility disorders after surgery for retinitis pigmentosa 'Cuba-therapy'.

Since 1988 Cuban ophthalmologists use a combined 'therapy' for retinitis pigmentosa. The treatment, comprising ozonization, electrostimulation, vasodilators, and an unknown surgical procedure after O. Pelaez, is said to stop the progression of the disease. While the nature of the operation remains unclear and scientific proof of its efficacy is still absent, reports about persisting active and passive impairments of ocular motility are becoming more frequent. The authors present the pre-, intra- and postoperative findings in two patients who developed persisting diplopia after Pelaez's operation. In both cases, one with +14° esotropia, the other with up to 25° incyclotropia and bilateral Brown's syndrome, binocular single vision was restored by recession of the medial rectus and superior oblique muscles. Comparing the functional findings before and one year after 'Cuba-therapy', the treatment fails to prevent progressive loss of visual acuity and visual field. Therefore, the Cuban treatment trial should not be recommended in retinitis pigmentosa.