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Background/aim: Blood flow deficiencies of the retinal and retrobulbar circulations have been previously reported in open-angle glaucoma (OAG) and other eye diseases. Herein we investigated the effects of image brightness and contrast dynamic altering stimuli (DAS) when viewing a video content on ocular blood flow, intraocular pressure (IOP) and ocular perfusion pressure (OPP) in OAG and healthy subjects., Methods: Thirty-five subjects, 25 with OAG (mild to moderate) and 10 healthy controls, were evaluated for blood pressure, IOP, OPP and retinal capillary blood flow before, immediately after, 30 min after and 60 min after using ReviView (a dichoptic video goggles device), which stimulates one eye with a DAS video image that is brighter and with greater contrast than the fellow eye (duration of exposure 30 min). Differences between each subject's eyes and between OAG and healthy subjects were evaluated using repeated-measures analysis of variance with p<0.05 considered statistically significant., Results: All subjects demonstrated a significant increase in OPP in both eyes immediately following viewing. In all DAS eyes, retinal capillary blood flow rose immediately after stimulation and remained elevated for an hour postviewing. Viewing DAS increased retinal blood flow compared with control eyes (p=0.0014, 0.0135 superiorly and p=0.0094, 0.0001 inferiorly, at 30 and 60 min, respectively). OAG eyes had a significant reduction in the number of dormant retinal capillaries (p=0.0174), while healthy eyes demonstrated a larger increase in retinal capillary blood flow (p=0.0006 and p=0.0093 at 60 min, superior and inferior, respectively) following DAS viewing., Conclusion: Viewing DAS video for 30 min using ReviView increased retina blood flow both in healthy subjects and in patients with OAG., Trial Registration Number: NCT02959593., Competing Interests: Competing interests: AH would like to disclose that he receives remuneration from CIPLA, AdOM and Shire for serving as a consultant. AH also holds an ownership interest in AdOM and Oxymap. All relationships listed above are pursuant to Indiana University’s policy on outside activities.​ The contribution of ACVV was supported by Fondazione Roma and by the Italian Ministry of Health., (© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

A new setup for high precision, automated secondary pH measurements together with a reference measurement procedure has been developed and tested in interlaboratory comparisons using buffers pH 4.005, pH 7.000, and pH 10.012 at 25 °C and 37 °C. Using primary buffers as standards, a standard uncertainty in pH better than 0.005 can be reached. The central measuring device is a one piece, thermostatted cell of PFA (perfluoroalkoxy) with a built-in Hamilton(®) Single Pore™ Glass electrode. Due to its flow-through principle this device allows pH measurements with low consumption of measurement solutions. The very hydrophobic and smooth PFA as construction material facilitates complete emptying of the cell. Furthermore, the tempering unit affords very precise temperature control and hence contributes to the low target uncertainty of the produced secondary buffer solutions. Use of a symmetric measurement sequence and the two point calibration was sufficient to reach high precision and accuracy.

The effect of exposure concentration on halothane metabolism was studied in rats exposed to subanesthetic concentrations of halothane in air. Concentrations of halothane, total nonvolatile fluorine, and volatile metabolites (CF3CH2Cl and CF2 = CHCl) were determined in liver, kidneys, muscles, and brains excised at the end of a 3-hr exposure. It was observed that concentrations of all halothane metabolites in tissues rose less than exposure concentrations, that nonvolatile fluorine was present in all tissues in approximately the same concentrations, and that concentrations of volatile metabolites in liver were much higher than in any other tissues. A simulation model was used to support the following conclusions. Metabolism of halothane by all metabolic pathways is flow limited at small exposure concentrations and is capacity limited at high exposure concentrations. Volatile metabolites formed in livers are efficiently removed from circulation by pulmonary clearance, but trifluoroacetic acid is accumulated in the body. Halothane is most susceptible to biodegradation to trifluoroacetic acid, but this pathway is saturated at very small exposure concentrations. Susceptibility to biodegradation of volatile metabolites is small, but the pathways are not saturated even at anesthetic concentrations. The contribution of each of the three metabolites to total metabolic clearance depends on exposure concentrations. Trifluoroacetic acid was the major metabolite during exposure to small halothane concentrations; formation of more toxic, volatile metabolites increased during exposure to high concentrations. Postmortem formation of metabolites was studied in order to prevent its interference with tissue analysis. The method for determination of volatile metabolites is described.