Retinal risk of endoillumination: A comparison of different ophthalmic illumination systems.

OBJECTIVES: In vitreoretinal surgery, there is always a conflict between bright illumination of the field of operation and retinal safety. This study aimed to investigate different light sources and light guides for their potential retinal risk due to bright illumination. METHODS: Irradiances in the fovea of ex-vivo porcine eyes resulting from different light sources (halogen lamp, xenon lamp and LED) and light guides are investigated for varying distances between the illumination tip and the fovea. The results are examined with regard to their photochemical and thermal retinal hazard and the maximal exposure time. The examination is carried out with the maximum intensity setting of each light source and with normalization to its brightness. MAIN RESULTS: With decreasing distance of the tip of the light source, the retinal hazard increases. The photochemical and thermal retinal hazard at maximum brightness are smallest for the halogen lamp, next for the xenon lamp and highest for the LED. Thus, the exposition time is the longest for the halogen lamp followed by the xenon lamp and the LED. Normalizing the results to the same brightness the maximum exposition time is nearly the same for xenon lamp and LED, but still higher in case of the halogen lamp. CONCLUSIONS: The choice of the most suitable lamp and illumination fiber depends on the intensity and spectral distribution of the illumination system. Concerning brightness, xenon and LED lamp are relatively harmless, but the surgeon should avoid the maximum device intensity.

[Ocular ischemic syndrome : An important differential diagnosis]. / Okuläres Ischämiesyndrom : Eine wichtige Differenzialdiagnose.

BACKGROUND: Ocular ischemic syndrome is a rare disease, which must be considered as a differential diagnosis in cases of painful loss of vision. CASE REPORT: A 63-year-old male patient presented as an emergency in our consultation with hyphemia and decompensated intraocular pressure of the right eye. The right eye had been painful for 3 weeks. Apart from nicotine abuse, no relevant pre-existing medical conditions were known. With suspected iritis, the initial treatment was performed with eye drops containing a corticosteroid. After initial improvement in symptoms, an acute deterioration occurred with decrease in visual acuity and increased pain starting 2 days previously. Biomicroscopic examination revealed rubeosis iridis with hyphemia. Due to the hyphemia the view of the fundus was greatly reduced but there were no indications for retinal bleeding. In gonioscopy a chamber angle closure was evident. Fluorescence angiography showed a significantly longer arm-retina time, a delayed arteriovenous passage, peripheral vascular leaks and reduced fluorescence of the choroid. An ocular ischemic syndrome was suspected, therefore, duplex sonography of the carotid arteries and computed tomography angiography were performed and showed complete stenosis of the right internal carotid artery and moderate stenosis of the left internal carotid artery. An intravitreal administration of anti-VEGF and panretinal laser photocoagulation were carried out. Furthermore, an evaluation of the cardiovascular risk factors was initiated as part of the interdisciplinary investigation.

Prevalence and impact of cannabis use disorders in adolescents with early onset first episode psychosis.

BACKGROUND: Previous studies on the impact of cannabis use disorders (CU) on outcome in psychosis were predominantly based on non representative samples, often have not controlled for confounders and rarely focused on adolescent patients. Thus, the aims of the present study were to assess: (i) prevalence of CU; (ii) baseline and pretreatment differences between CU and those without CU (NCU); (iii) the impact of baseline and course of CU on 18-month outcomes in a representative cohort of adolescents with early onset first episode psychosis (EOP). METHODS: The sample comprised 99 adolescents (age 14 to 18) with EOP (onset age 14 to 17), admitted to the Early Psychosis Prevention and Intervention Centre in Australia. Data were collected from medical files using a standardized questionnaire. RESULTS: Prevalence of lifetime CU was 65.7%, of current CU at baseline 53.5%, and of persistent CU throughout treatment 26.3%. Baseline CU compared to NCU had significantly higher illness-severity, lower psychosocial functioning, less insight, lower premorbid functioning and longer duration of untreated psychosis. Compared to all other groups, only persistent CU was linked to worse outcomes and more service disengagement. Effect sizes were medium controlling for relevant confounders. Medication non-adherence did not explain the association between persistent CU and worse outcome. CONCLUSIONS: Baseline CU was associated with worse baseline characteristics, but only persistent CU was linked with worse outcome. About half of those with baseline CU reduced cannabis during treatment. For these, effectively treating the psychotic disorder may already be beneficial. However, future research is necessary on the reasons for persistent CU in EOP and its treatment.

[Can the cutting performance of trephines still be improved?]. / Kann die Schnittqualität von Trepanen noch verbessert werden? Anwendung nanotechnologischer Verfahren zur Herstellung von Trepanen mit diamantähnlichen Schneidkanten.

PURPOSE: Today, for the preparation of donor and recipient cornea during keratoplasty either single-use or reusable metal trephines are commonly used although excimer and femtosecond laser systems are available. Due to the surgical techniques as well as the configuration of metal trephine's cutting edge irregular corneal surfaces may be induced. These will result in a postoperative astigmatism. Contemporary manufacturing processes do allow for the production of minimal cutting edge diameters (400 nm -- 1 microm), however, this is related with a reduced mechanical stability of such delicate cutting edges. It has been observed that the cutting edge of metal blades is immediately bent with the first exposure to tissue. As a result, the cutting forces are increasing and the wound configuration is negatively effected. Due to the complex geometry of trephine cutting edges, no diamond trephines are currently available. We are investigating the cutting performance of conventional trephines that were modified using nanotechnology. METHOD: Different metal trephines were characterised using a scanning electron microscope (SEM). The diameter of the cutting edge was measured. Pig cornea were studied histologically after trepanation. Selected trephines were ion-forged in a modified PVD (physical vapour deposition) reactor using highly accelerated ions which are concentrated by magnetic fields at low temperature. The consecutive processing steps were controlled by SEM analysis of the cutting edge diameters. Randomly chosen areas of treated trephines were analysed. After processing the trephines, pig cornea were cut and analysed by histological and SEM examination. Additionally, the relevant mechanical cutting parameters of untreated as well as treated trephines were measured when penetrating into a PU (polyurethane) foil. RESULTS: Preliminary microscopic analysis already reveals differences in the quality of the cutting edges. The nanotechnological modification of the cutting edges does not result in larger diameters. Compared with the initial cutting edges, the optical analysis of the modified trephine cutting edges reveals subjectively smoother surfaces. The force measurements prove a reduction of cutting forces for the treated trephines compared to the untreated ones. The SEM analysis show for the cornea treated with the modified trephines a subjectively smoother surface. Histology reveals that the surfaces of the treated cornea do not exhibit a smooth and unidirectional structure. This divergence became larger when untreated trephines were used. The mechanical characterisation of the treated trephines resulted in harder and longer-lasting surfaces. DISCUSSION: The newly developed ion-forging of trephines in combination with nanostructured carbon coatings yield complex cutting edges of higher stability with diamond-like properties. This study shows that the performance of laser trepanation cannot be reached; however, the use of nanotechnology can further improve manual trephine techniques.

St John's wort (Hypericum perforatum) modulates evoked potentials in guinea pig hippocampal slices via AMPA and GABA receptors.

The effects of an ethanolic extract of the plant Hypericum perforatum L. (St John's wort) (HYP) and its hydrosoluble fraction (HYPWS) on electrically evoked population spikes and fEPSP were investigated in this study. Concentration dependent (10(-6) to 10(-4) g/l) excitatory effects were found. Above concentrations of 10(-3) g/l, HYP reduced the evoked responses, whereas HYPWS further increased them. Paired pulse facilitation was unaffected with HYPWS (10(-4) to 10(-2) g/l). The excitatory effects of HYPWS were amplified by the GABA(A) and GABA(B) receptor antagonists bicuculline and phaclofen, respectively. These excitations were antagonised by the AMPA receptor antagonist CNQX. Excitations caused by hypericum were not antagonised by the NMDA receptor antagonists D-APV and MK801, the metabotropic glutamate receptor (type I and II) antagonist MCPG, or the L-type calcium channel blocker verapamil. Hypericin and hyperforin, two components of H. perforatum, were found not to be responsible for the excitatory effects of the extract.

Alterations of hippocampal acetylcholinesterase in human temporal lobe epilepsy.

Hippocampal sclerosis is the most common pathological finding associated with human temporal lobe epilepsy. Histochemical study with acetylcholinesterase (AChE) staining was used to investigate 7 surgically resected temporal lobes with hippocampal sclerosis from patients with temporal lobe epilepsy. In all 7 specimens, an abnormal but consistent pattern of staining was noted. In the hilum of the dentate gyrus, AChE-rich polymorphic cells were relatively preserved in comparison to the pyramidal neurons. In Ammon's horn, AChE fibers were lost in regions corresponding to the pyramidal cell dropout. AChE fibers were also lost along the inner portion of the molecular layer of the dentate gyrus, yet they were preserved within the outer portions of the molecular layer. These findings provide additional evidence for the relative selectivity of hippocampal pathology in human temporal lobe epilepsy.