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Inwardly rectifying K+ channel Kir7.1 is expressed in epithelia where it shares membrane localisation with the Na+/K+-pump. The ciliary body epithelium (CBE) of the eye is a determinant of intraocular pressure (IOP) through NaCl-driven fluid secretion of aqueous humour. In the present study we explored the presence Kir7.1 in this epithelium in the mouse and its possible functional role in the generation of IOP. Use heterozygous animals for total Kir7.1 knockout expressing ß-galactosidase under the control of Kir7.1 promoter, identified the expression of Kir7.1 in non-pigmented epithelial cells of CBE. Using conditional, floxed knockout Kir7.1 mice as negative controls, we found Kir7.1 at the basolateral membrane of the same CBE cell layer. This was confirmed using a knockin mouse expressing the Kir7.1 protein tagged with a haemagglutinin epitope. Measurements using the conditional knockout mouse show only a minor effect of Kir7.1 inactivation on steady-state IOP. Transient increases in IOP in response to general anaesthetics, or to water injection, are absent or markedly curtailed in Kir7.1-deficient mice. These results suggest a role for Kir7.1 in IOP regulation through a possible modulation of aqueous humour production by the CBE non-pigmented epithelial cells. The location of Kir7.1 in the CBE, together with the effect of its removal on dynamic changes in IOP, point to a possible role of the channel as a leak pathway preventing cellular overload of K+ during the secretion process. Kir7.1 could be used as a potential therapeutic target in pathological conditions leading to elevated intraocular pressure.

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BACKGROUND: To assess the sensitivity, specificity, positive predictive value and negative predictive value of anterior chamber tap for the diagnosis of bacterial endophthalmitis on a population with high prevalence. METHODS: Retrospective, single centre, case series study. We reviewed all medical records with clinical diagnosis of bacterial endophthalmitis in our hospital from January 1st, 2000 to December 31st 2014. From each record, we documented general demographic data, best corrected visual acuity and vitreous and aqueous tap microbiological results. All cases were further divided according to the endophthalmitis aetiology to perform individual calculations of sensitivity, specificity, positive predictive value, negative predictive value, accuracy and prevalence. We used the results of the vitreous tap as the gold standard for diagnosis of bacterial endophthalmitis. We excluded those records in which the aqueous and vitreous samples were not taken simultaneously or had an incomplete microbiological report. Significance were assessed with chi squared statistics, with an alpha value of 0.05 for statistical significance. RESULTS: A total of 190 cases fulfilled the inclusion/exclusion criteria. Positive culture rate from vitreous samples was 64.74%. Positive culture rate from aqueous sample was 32.11%. Bacteria isolated from aqueous samples matched those isolated from vitreous samples 78.68% of the time. The overall sensitivity was 38.21%, specificity: 75.51%, positive predictive value: 79.66%, negative predictive value: 32.74% (p = 0.08). Subgroup analysis showed that anterior chamber taps in cases of post-surgical endophthalmitis had a moderate to low sensitivity (37.73%), high specificity (93%) and high positive predictive value (95%) (p < 0.04). CONCLUSION: The sensitivity and specificity of anterior chamber tap are low and should not be used for critical therapeutic decisions in patients with suspected bacterial endophthalmitis. In cases of post-surgical endophthalmitis, the result of an anterior chamber tap could be used for therapeutic guidance, but only in conjunction with clinical presentation and in the absence of a better method for diagnosis.

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Intraocular pressure (IOP) peaks and means have been considered important factors for glaucoma onset and progression. However, peak IOP detection depends only on appropriated IOP checks at office visits, whereas the mean IOP requires longitudinal IOP data collection and may be affected by the interval between visits. Also, IOP peak assessment is necessary to verify if the peak pressure of a given patient is in target range, to evaluate glaucoma suspect risk, the efficacy of hypotensive drugs and to detect early loss of IOP control. The water-drinking test has gained significant attention in recent years as an important tool to evaluate IOP peaks and instability. The main objective of this review was to present new findings and to discuss the applicability of the water-drinking test in glaucoma management.

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