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AIMS: To analyse the changes in endothelial cell density (ECD) after pars plana vitrectomy (PPV) and to identify the factors implicated. PATIENTS AND METHODS: This was a prospective, consecutive, and non-randomised, case-control study. All 23-gauge vitrectomies were performed by a single surgeon at a tertiary centre. ECD was measured at baseline before surgery and on postoperative Days 30, 90, and 180. The fellow eye was used as the control eye. The primary outcome was a change in ECD after PPV. RESULTS: Seventeen patients were included in this study. The mean age of the patients was 65 years. The mean ECD count at baseline was 2340 cells/mm2. The median ECD loss in the vitrectomised eye was 3.6 %, 4.0 %, and 4.7 % at Days 30, 90, and 180, respectively, compared to +1.94 %, +0.75 %, +1.01 %, respectively, in the control eye. The relative risk of ECD loss after PPV was 2.48 (C.I. 1.05-5.85, p = 0.0247). The pseudophakic eyes lost more ECD than the phakic eyes, but this was not statistically significant. There were no significant differences in diagnosis, age, surgical time, or tamponade used after surgery. CONCLUSIONS: Routine pars plana vitrectomy had an impact on the corneal endothelial cells until Day 180 post-op. The phakic status was slightly protective against ECD loss after PPV, although it was not statistically significant. The pathophysiology of corneal cell damage after routine PPV remains unclear. Further studies are required to confirm these findings.

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The photodissociation dynamics of bromochloromethane (CH2BrCl) have been investigated at the maximum of the first absorption band, at the excitation wavelengths 203 and 210 nm, using the slice imaging technique in combination with a probe detection of bromine-atom fragments, Br(2P3/2) and Br*(2P1/2), via (2 + 1) resonance enhanced multiphoton ionization. Translational energy distributions and angular distributions reported for both Br(2P3/2) and Br*(2P1/2) fragments show two contributions for the Br(2P3/2) channel and a single contribution for the Br*(2P1/2) channel. High level ab initio calculations have been performed in order to elucidate the dissociation mechanisms taking place. The computed absorption spectrum and potential energy curves indicate the main contribution of the populated 4A″, 5A', and 6A' excited states leading to a C-Br cleavage. Consistently with the results, the single contribution for the Br*(2P1/2) channel has been attributed to direct dissociation through the 6A' state as well as an indirect dissociation of the 5A' state requiring a 5A' → 4A' reverse non-adiabatic crossing. Similarly, a faster contribution for the Br(2P3/2) channel characterized by a similar energy partitioning and anisotropy than those for the Br*(2P1/2) channel is assigned to a direct dissociation through the 5A' state, while the slower component appears to be due to the direct dissociation on the 4A″ state.

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The photodissociation dynamics of the methyl iodide cation has been studied using the velocity map imaging technique. A first laser pulse is used to ionize methyl iodide via a (2 + 1) REMPI scheme through the 5pπ → 6p Rydberg state two-photon transition. The produced CH3I+(X[combining tilde]2E3/2) ions are subsequently excited at several wavelengths between 242 and 260 nm. The reported translational energy distributions for the methyl and iodine ions present a Boltzmann-type unstructured distribution at low excitation energies as well as a recoiled narrow structure at higher excitation energies highlighting two different dissociation processes. High level ab initio calculations have been performed in order to obtain a deeper understanding of the photodissociation dynamics of the CH3I+ ion. Direct dissociation on a repulsive state from the manifold of states representing the B[combining tilde] excited state leads to CH3+(X[combining tilde]1A1') + I*(2P1/2), while the CH3 + I+(3P2) channel is populated through an avoided crossing outside the Franck-Condon region. In contrast, an indirect process involving the transfer of energy from highly excited electronic states to the ground state of the ion is responsible for the observed Boltzmann-type distributions.

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The authors present a case report of a 20-year-old patient with an atypical clinical picture of bilateral vasculitis associated with bilateral macular oedema and decrease in visual acuity. On basis of the clinical picture, frosted branch angiitis was diagnosed. The patient was instructed to continue the broad-spectrum antibiotic therapy prescribed by an ophthalmic practitioner of the appropriate catchment area. The visual acuity progressively improved and after application of systemic corticosteroid therapy the patients health state improved completely. According to the authors knowledge, this is the first diagnosed case of frosted branch angiitis in the Slovak Republic.

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The disease epilepsy is related to hypersynchronous activity of networks of neurons. While acute epileptic seizures are the most extreme manifestation of this hypersynchronous activity, an elevated level of interdependence of neuronal dynamics is thought to persist also during the seizure-free interval. In multichannel recordings from brain areas involved in the epileptic process, this interdependence can be reflected in an increased linear cross correlation but also in signal properties of higher order. Bivariate time series analysis comprises a variety of approaches, each with different degrees of sensitivity and specificity for interdependencies reflected in lower- or higher-order properties of pairs of simultaneously recorded signals. Here we investigate which approach is best suited to detect putatively elevated interdependence levels in signals recorded from brain areas involved in the epileptic process. For this purpose, we use the linear cross correlation that is sensitive to lower-order signatures of interdependence, a nonlinear interdependence measure that integrates both lower- and higher-order properties, and a surrogate-corrected nonlinear interdependence measure that aims to specifically characterize higher-order properties. We analyze intracranial electroencephalographic recordings of the seizure-free interval from 29 patients with an epileptic focus located in the medial temporal lobe. Our results show that all three approaches detect higher levels of interdependence for signals recorded from the brain hemisphere containing the epileptic focus as compared to signals recorded from the opposite hemisphere. For the linear cross correlation, however, these differences are not significant. For the nonlinear interdependence measure, results are significant but only of moderate accuracy with regard to the discriminative power for the focal and nonfocal hemispheres. The highest significance and accuracy is obtained for the surrogate-corrected nonlinear interdependence measure.

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Spectral measures of causality are used to explore the role of different rhythms in the causal connectivity between brain regions. We study several spectral measures related to Granger causality, comprising the bivariate and conditional Geweke measures, the directed transfer function, and the partial directed coherence. We derive the formulation of dependence and causality in the spectral domain from the more general formulation in the information-theory framework. We argue that the transfer entropy, the most general measure derived from the concept of Granger causality, lacks a spectral representation in terms of only the processes associated with the recorded signals. For all the spectral measures we show how they are related to mutual information rates when explicitly considering the parametric autoregressive representation of the processes. In this way we express the conditional Geweke spectral measure in terms of a multiple coherence involving innovation variables inherent to the autoregressive representation. We also link partial directed coherence with Sims' criterion of causality. Given our results, we discuss the causal interpretation of the spectral measures related to Granger causality and stress the necessity to explicitly consider their specific formulation based on modeling the signals as linear Gaussian stationary autoregressive processes.

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AIMS: To compare anatomical and functional outcomes for 546 phakic and pseudophakic primary rhegmatogenous retinal detachments (RDs) treated by pars plana vitrectomy or scleral buckling. METHODS: Prospective, non-randomised, interventional study in 15 centres in Spain and Portugal, with data from RDs consecutively treated from January 2005 to May 2007. Cases with preoperative proliferative vitreoretinopathy grade C-1 or higher and perforating trauma were excluded. Minimum follow-up was 3 months. Twenty-seven pre-, intra- and post-surgical variables for each patient were analysed. Multivariate analysis was carried out by logistic regression analysis with stepwise selection of variables. RESULTS: Data from 546 patients were analysed. Global anatomical success was 94.7%. Logistic regression analysis showed that only the development of postoperative proliferative vitreoretinopathy was associated with a poor anatomical outcome. The poorest functional results were associated with macular involvement, extension of RD, previous RD surgery, time of evolution of RD, and age of patient. Hierarchical log-linear analysis showed no effect of the lens status (phakic versus pseudophakic) on the functional results. However, pars plana vitrectomy was most often performed in pseudophakic eyes and resulted in a worse final visual acuity (p<0.001). CONCLUSIONS: No differences in anatomical success between phakic and pseudophakic eyes were found in this series. Pars plana vitrectomy was most often performed in pseudophakic eyes and had a greater probability of a worse final visual acuity than scleral buckling.

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