Development of a very large array for retinal stimulation

Retina degeneration is one of the leading causes of blindness nowadays and cannot be cured in most cases. It has been shown that electrical stimulation of retinal ganglion cells can generate visual perceptions and therefore implantable electrode arrays can be possible treatment for these patients. Most implants developed for that purpose use electrode arrays with a size of a few millimeters squared and therefore could restore only a very small field of vision and hardly improve orientation in an unknown environment. In this paper we present results of the development of an implantable electrode array covering about 100 mm(2) of retinal tissue.

Implantation and explantation of an active epiretinal visual prosthesis: 2-year follow-up data from the EPIRET3 prospective clinical trial

PURPOSE

The EPIRET3 retinal prosthesis was implanted in six volunteers legally blind from retinitis pigmentosa (RP) and removed after 4 weeks. Two years later, these subjects were re-examined to investigate ocular side effects and potential changes to quality of life.

METHODS

Vision-related quality of life was recorded using the NEI-VFQ-25 questionnaire. Clinical data including interval history, visual acuity, and intraocular pressure were obtained. Anterior and posterior segments of the study eyes were examined and photographed; this included fluorescein angiography and optical coherence tomography (OCT).

RESULTS

Data from five patients could be analysed. Life-quality score was consistent with results obtained at baseline. No unexpected structural alteration could be found in the study eyes. A moderate epiretinal gliosis was present in areas where the epiretinal stimulator had been fixated using retinal tacks. Angiography revealed no leakage or neovascularisation; OCT showed no generalised increase of central retinal thickness.

CONCLUSIONS

Vision-related quality of life is low in patients suffering from end-stage RP. No further deterioration of life quality could however be detected within our monitoring period. Surgery was well tolerated by both patients and their eyes, without adverse events occurring during the follow-up period. Epiretinal gliosis is known to occur with retinal tacks, but seems of no major concern to the integrity of the study eyes. However, it may potentially interfere with functional aspects of active implants. Hence, alternative, possibly biochemical, fixation methods merit further research.

Neuromonitoring in a porcine model of acute hepatic failure

Cerebral oedema has been noted to occur frequently in patients dying of fulminant hepatic failure. Therefore, in the present study, multimodal neuromonitoring was evaluated in an animal model of hepatectomy. Acute liver failure was surgically induced in swine by complete hepatectomy (n = 8). Intracranial pressure monitoring via a ventricular drainage system, electroencephalogram and recording of visually evoked potentials were used to establish a continuous neuromonitoring system. Measurements of liquor and serum ammonia (NH(3)) levels were taken at later stages of the trial in an approach to widen monitoring. Serial monitoring of the electroencephalogram revealed progressive slowing of the frequency with decreasing amplitude. Monitoring of the intracranial pressure with a subdural pressure transducer demonstrated a progressive and reproducible elevation. Increase in blood NH(3) was observed. Anaesthesia was terminal. In all cases death was caused by cardiocirculatory insufficiency, confirmed by autopsy. At autopsy, brain tissue of the animals was found to be swollen showing flattened cortical gyri. In conclusion, the technique of extended neuromonitoring offers an advanced option for monitoring animal models of fulminant hepatic failure for further developments and investigations.

[Surgical treatment of esophageal cancer]

Prospective study, included 117 patients with esophageal cancer, all received resection of the esophagus through laparatomy and and right-side thoracotomy without neoadjuvant chemotherapy. 70,0% of patients demonstrated stage higher then IIb UICC. R0 resection was possible in 101 patients (86,3%). Hospital lethality was 5,1%. Overall lethality among the operated patients was 21,4%. Long-term follow-up results were obtained in 96,6%. Surgical treatment alone does not provide satisfactory results for the patients with cancer of esophagus. Further therapy individualization and combination of surgery with modern neoadjuvant chemotherapy can provide better prognosis for these patients.

Nursery pollination by a moth in Silene latifolia: the role of odours in eliciting antennal and behavioural responses

Since the 1970s it has been known that the nursery pollinator Hadena bicruris is attracted to the flowers of its most important host plant, Silene latifolia, by their scent. Here we identified important compounds for attraction of this noctuid moth. Gas chromatographic and electroantennographic methods were used to detect compounds eliciting signals in the antennae of the moth. Electrophysiologically active compounds were tested in wind-tunnel bioassays to foraging naïve moths, and the attractivity of these compounds was compared with that to the natural scent of whole S. latifolia flowers. The antennae of moths detected substances of several classes. Phenylacetaldehyde elicited the strongest signals in the antennae, but lilac aldehydes were the most attractive compounds in wind-tunnel bioassays and attracted 90% of the moths tested, as did the scent of single flowers. Our results show that the most common and abundant floral scent compounds in S. latifolia, lilac aldehydes, attracted most of the moths tested, indicating a specific adaptation of H. bicruris to its host plant.

[Development of an epiretinal prosthesis for stimulation of the human retina]

Degenerations of the outer retina in retinal diseases such as retinitis pigmentosa lead to blindness due to photoreceptor loss. A therapeutic option for visual rehabilitation is presently not available. Over the last few years, a retinal prosthesis has been developed and its use has been tested in animal experiments as well as in humans. With the epiretinal implant images of the environment are taken by a camera, these data are transmitted to an intraocular encoder, and the retina is electrically stimulated by a retinal stimulator placed epiretinally. The stimulation electrodes are placed as flexible microcontact electrodes by pars plana vitrectomy in an epimacular position. The threshold is determined by stimulations of increasing amplitudes. Initial results of acute epiretinal stimulation using an epiretinal implant in legally blind patients demonstrate that acute epiretinal stimulation of the human retina is feasible and safe.

Determination of surgeon's absorbed dose in iodine 125 and ruthenium 106 ophthalmic plaque surgery

OBJECTIVE

Validation of dosimetry and exposition time to an ophthalmic surgeon during radioactive plaque operations.

DESIGN

Experimental study in which videotaped operations and dosimetric measurements were used to model dosimetry.

METHODS

We used thermoluminescence detectors for high sensitivity readings in radiation fields. Typical intersurgical mobility was videotaped and distances to the plaque was evaluated.

MAIN OUTCOME MEASURE

Estimated radiation received by surgeons.

RESULTS

All simulated plaque operations have a maximum dose rate of 6 mGy per minute (value in the inner eyeball). Mean dose rate is 2 mGy per minute (average of approximately all measurements). The surgeon's fingers receive a dose from 2 to 6 mSv from plaque operation.

CONCLUSIONS

Results suggest that radioactive plaque operations are safe for the surgeon but that the time for plaque handling should be minimized. A surgeon should not exceed 100 to 200 operations per year.