Peter Szurman

Subretinal electronic chips allow blind patients to read letters and combine them to words

A light-sensitive, externally powered microchip was surgically implanted subretinally near the macular region of volunteers blind from hereditary retinal dystrophy. The implant contains an array of 1500 active microphotodiodes (‘chip’), each with its own amplifier and local stimulation electrode. At the implants tip, another array of 16 wire-connected electrodes allows light-independent direct stimulation and testing of the neuron–electrode interface. Visual scenes are projected naturally through the eyes lens onto the chip under the transparent retina. The chip generates a corresponding pattern of 38 × 40 pixels, each releasing light-intensity-dependent electric stimulation pulses. Subsequently, three previously blind persons could locate bright objects on a dark table, two of whom could discern grating patterns. One of these patients was able to correctly describe and name objects like a fork or knife on a table, geometric patterns, different kinds of fruit and discern shades of grey with only 15 per cent contrast. Without a training period, the regained visual functions enabled him to localize and approach persons in a room freely and to read large letters as complete words after several years of blindness. These results demonstrate for the first time that subretinal micro-electrode arrays with 1500 photodiodes can create detailed meaningful visual perception in previously blind individuals.

Transplantation of iris pigment epithelium into the choroid slows down the degeneration of photoreceptors in the RCS rat.

Abstractu2002Background:Trophic factors [e.g. basic fibroblast growth factor (bFGF)] released by transplanted retinal pigment epithelial (RPE) cells are able to slow down the hereditary degeneration of the retina in the Royal College of Surgeons rat in sites distant from the site of transplantation where rod outer segment (ROS) phagocytic activity is not reconstituted by the transplants. Methods:To investigate whether iris pigmented epithelial (IPE) cells are also able to generate this rescue by trophic factors, we transplanted IPE cells from Long-Evans rats into the choroid and subretinal space of 17 young RCS rats. The eyes were enucleated after 6 months and prepared for light microscopy. Six age-matched RCS rats served as controls. Light microscope sections from the whole choroid, healthy choriocapillaris, transplanted cells and the maximum thickness of the choroid, and outer nuclear layer parameters were analyzed by computer-assisted morphometry. Results:In transplanted animals photoreceptor cells were rescued from degeneration although the majority of the transplanted IPE cells were located in the choroid. In the non-transplanted group photoreceptors were absent. Conclusions:Transplantation of IPE cells slows down degeneration of the photoreceptors in the RCS rat. This photoreceptor-sparing effect by the IPE cells was observed even when the transplants were predominantly located within the choroid. The beneficial effect observed may be related to trophic factors possibly secreted by the transplanted IPE cells.

Typical Ultrasound Biomicroscopic Findings Seen in Ocular Hypotony

Detailed imaging of the ciliary body region by means of ultrasound biomicroscopy can provide information that is crucial for further treatment whereas clinical evaluation and 10-MHz standard B scan are less helpful. Background: To evaluate the suitability of ultrasound biomicroscopy (UBM) for elucidating the causes of ocular hypotony. Patients and Methods: A retrospective chart review was performed to determine the usefulness of UBM in the evaluation of ocular hypotony. UBM, B scan, and a detailed clinical examination had been performed. Sixty patient charts with prolonged ocular hypotony of different causes were reviewed from January 1994 to December 1998. The information obtained by the UBM was classified into three groups: ‘diagnostic’ (group 1), ‘helpful’ (group 2), ‘not helpful’ (group 3). Results: Of the 60 eyes, 45 UBM examinations (75%) were in group 1, 9 eyes (15%) were assigned to group 2 and 6 eyes (10%) were in group 3. The duration of hypotony had no influence. Conclusion: In cases of ocular hypotony, the cause was related to ciliary body pathologies in 80%. Only UBM could distinguish tractional from dehiscence ciliary body detachment which required a different management approach. UBM with its high resolution imaging of the anterior segment – including the ciliary body – is highly suitable for diagnostic clarification.

Experimental Implantation of Devices for Electrical Retinal Stimulation In Rabbits

In the treatment of progressive receptor degenerations of the human retina e.g. in retinitis pigmentosa (RP) the electrical stimulation of nerve fibers of retinal ganglion cells is discussed as one possible option. It was reported that blind patients suffering from a massive photoreceptor dysfunction had a kind of visual perception when a stimulating current was applied to the inner retinal surface1. With an implanted array of microcontacts it should be possible to evoke a visual response featuring a minimum of spatial resolution in these patients. One prerequisite for this kind of treatment is the existance of a sufficient number of intact ganglion cell fibers which was shown by Stone and coworkers’. Another prerequisite for this concept of a future RP treatment is that the stimulator could be implanted into the eye and onto the inner surface of the retina. The device has to be biocompatible and it should not change its position on the retina once being implanted.

Contact Lens, Hyperopia and Endothelial Changes

Introduction: We report on a 62-year-old healthy woman who suffered from bilateral predescemetic opacities, where the underlying disorder could not be identified. She had bilateral keratopathy with corneal edema, a diffuse predescemetic avascular haze and deszemetic folds. Because of high hyperopia (right +7.50/left +7.75) she weared soft contact lenses for years. Methods: Removal of contact lenses. Treatment with local steroids and tear substitutes.Results: One year after cessation of contact lenses VA recovered from RE 0.3/LE 0.1 to 0.8/0.63, the deep stromal opacity cleared up, the corneal edema recessed slightly. Discussion: The differential diagnosis concludes either a pure contact lens change that is not completely reversible or a possible posterior polymorphous dystrophy that worsens with long-term contact lens wear and improves on cessation.

Book Reviews · Livres nouveaux · Buchbesprechungen

Conjunctival inflammation is one of the most frequent conditions presenting to the ophthalmologist. While in the past decades, bacterial infections of the conjunctiva have become much easier to diagnose and treat, the non-infectious disorders still pose confounding problems. Inflammatory Diseases of the Conjunctiva provides an in-depth review of the pathological mechanisms causing these diseases. The strength of this book lies in its presentation of immunological knowledge which is indispensable for the understanding of conjunctival inflammation. As immunology is a very dynamic field of research, the authors put great emphasis on giving up-to-date information on basic research findings and putting them in perspective regarding their clinical relevance. In this the book is of great value for the clinician. It is also very well structured, dealing with individual disease entities in separate chapters and providing sections on laboratory investigations, differential diagnosis and treatment options in each of them. Some topics are given special consideration in ‘focus’ sections, among them dry eye syndrome, laboratory investigations of conjunctival inflammation and apoptosis in the conjunctiva. Dr. Holger Baatz, Frankfurt G.A. Fishman, D.G. Birch, G.H. Holder, et al.