Correlation between visual function and visual ability in patients with uveitis

Aim: To investigate the correlation between tests of visual function and perceived visual ability recorded with a quality of life questionnaire for patients with uveitis. Methods: 132 patients with various types of uveitis were studied. High (monocular and binocular) and low (binocular) contrast logMAR letter acuities were recorded using a Bailey-Lovie chart. Contrast sensitivity (binocular) was determined using a Pelli-Robson chart. Vision related quality of life was assessed using the Vision Specific Quality of Life (VQOL) questionnaire. Results: VQOL declined with reduced performance on the following tests: binocular high contrast visual acuity (p = 0.0011), high contrast visual acuity of the better eye (p = 0.0012), contrast sensitivity (p = 0.005), binocular low contrast visual acuity (p = 0.0065), and high contrast visual acuity of the worse eye (p = 0.015). Stepwise multiple regression analysis revealed binocular high contrast visual acuity (p <0.01) to be the only visual function adequate to predict VQOL. The age of the patient was also significantly associated with perceived visual ability (p <0.001). Conclusions: Binocular high contrast visual acuity is a good measure of how uveitis patients perform in real life situations. Vision quality of life is worst in younger patients with poor binocular visual acuity.

The effect of corneal thickness and corneal curvature on pneumatonometer measurements

Purpose. The purpose of this study was to investigate the influence of corneal topography and thickness on intraocular pressure (IOP) and pulse amplitude (PA) as measured using the Ocular Blood Flow Analyzer (OBFA) pneumatonometer (Paradigm Medical Industries, Utah, USA). Methods. 47 university students volunteered for this cross-sectional study: mean age 20.4 yrs, range 18 to 28 yrs; 23 male, 24 female. Only the measurements from the right eye of each participant were used. Central corneal thickness and mean corneal radius were measured using Scheimpflug biometry and corneal topographic imaging respectively. IOP and PA measurements were made with the OBFA pneumatonometer. Axial length was measured using A-scan ultrasound, due to its known correlation with these corneal parameters. Stepwise multiple regression analysis was used to identify those components that contributed significant variance to the independent variables of IOP and PA. Results. The mean IOP and PA measurements were 13.1 (SD 3.3) mmHg and 3.0 (SD 1.2) mmHg respectively. IOP measurements made with the OBFA pneumatonometer correlated significantly with central corneal thickness (r = +0.374, p = 0.010), such that a 10 mm change in CCT was equivalent to a 0.30 mmHg change in measured IOP. PA measurements correlated significantly with axial length (part correlate = -0.651, p < 0.001) and mean corneal radius (part correlate = +0.459, p < 0.001) but not corneal thickness. Conclusions. IOP measurements taken with the OBFA pneumatonometer are correlated with corneal thickness, but not axial length or corneal curvature. Conversely, PA measurements are unaffected by corneal thickness, but correlated with axial length and corneal radius. These parameters should be taken into consideration when interpreting IOP and PA measurements made with the OBFA pneumatonometer.

Effect of β-adrenoceptor antagonists on autonomic control of ciliary smooth muscle

Purpose: Pharmacological intervention with peripheral sympathetic transmission at ciliary smooth muscle neuro-receptor junctions has been used against a background of controlled parasympathetic activity to investigate the characteristics of autonomic control of ocular accommodation. Methods: A continuously recording infrared optometer was used to measure accommodation on a group of five visually normal emmetropic subjects under open- and closed-loop conditions. A double-blind protocol between saline, timolol and betaxolol was used to differentiate between the localised action on ciliary smooth muscle and effects induced by changes in stimulus conditions. Data were collected before and 45 min following the instillation of saline, timolol or betaxolol. Open-loop post-task decay was investigated following 3 min sustained near fixation of a stimulus placed 3 D above the subject's pre-task tonic accommodation level. Closed-loop dynamic responses were recorded for each treatment condition while subjects viewed sinusoidally (0.05-0.6 Hz) or stepwise vergence-modulated targets over a 2 D range (2-4 D). Results: Open-loop data demonstrate a rapid post-task regression to pre-task tonic accommodation levels for saline and betaxolol control conditions. A slow positive post-task shift was induced by timolol indicating that sympathetic inhibition contributes to accommodative adaptation during sustained near vision. Closed-loop accommodation responses to temporally modulated sinusoidal stimuli showed characteristic features for both saline and betaxolol control conditions. Timolol induced a reduced gain for low- and mid-temporal frequencies (< 0.3 Hz) but did not affect the response at higher temporal frequencies. Response times to stepwise stimuli increased following the instillation of timolol for the near-to-far fixation condition compared with the controls and was related to the period of sustained prior fixation. Conclusions: Modulation of accommodation under open- and closed-loop conditions by a non-selective β-blocker is consistent with the temporal and inhibitory features of sympathetic innervation to ciliary smooth muscle. Although parasympathetic innervation predominates there is evidence to support a role for sympathetic innervation in the control of ocular accommodation. © 2002 The College of Optometrists.

People, technology, processes and risk knowledge sharing

The present global economic crisis creates doubts about the good use of accumulated experience and knowledge in managing risk in financial services. Typically, risk management practice does not use knowledge management (KM) to improve and to develop new answers to the threats. A key reason is that it is not clear how to break down the “organizational silos” view of risk management (RM) that is commonly taken. As a result, there has been relatively little work on finding the relationships between RM and KM. We have been doing research for the last couple of years on the identification of relationships between these two disciplines. At ECKM 2007 we presented a general review of the literature(s) and some hypotheses for starting research on KM and its relationship to the perceived value of enterprise risk management. This article presents findings based on our preliminary analyses, concentrating on those factors affecting the perceived quality of risk knowledge sharing. These come from a questionnaire survey of RM employees in organisations in the financial services sector, which yielded 121 responses. We have included five explanatory variables for the perceived quality of risk knowledge sharing. These comprised two variables relating to people (organizational capacity for work coordination and perceived quality of communication among groups), one relating to process (perceived quality of risk control) and two related to technology (web channel functionality and RM information system functionality). Our findings so far are that four of these five variables have a significant positive association with the perceived quality of risk knowledge sharing: contrary to expectations, web channel functionality did not have a significant association. Indeed, in some of our exploratory regression studies its coefficient (although not significant) was negative. In stepwise regression, the variable organizational capacity for work coordination accounted for by far the largest part of the variation in the dependent variable perceived quality of risk knowledge sharing. The “people” variables thus appear to have the greatest influence on the perceived quality of risk knowledge sharing, even in a sector that relies heavily on technology and on quantitative approaches to decision making. We have also found similar results with the dependent variable perceived value of Enterprise Risk Management (ERM) implementation.

Macular pigment optical density is related to blood glutathione levels in healthy individuals

Purpose. To assess the relationship between macular pigment optical density (MPOD) and blood markers for antioxidant defense in otherwise healthy volunteers. Methods. Forty-seven healthy volunteers were subjected to blood analysis to detect the level of circulating glutathione in its reduced (GSH) and oxidized (GSSG) forms. The level of MPOD was measured using heterochromatic flicker photometry. Systemic blood pressure (BP) parameters, heart rate (HR), body mass index (BMI), and plasma levels of total, HDL, and LDL cholesterol and triglycerides (TGs) were also determined. Results. A simple correlation model revealed that the level of MPOD correlated significantly and positively with both GSH (P < 0.001) and t-GSH (P < 0.001) levels but not with those of GSSG (P > 0.05). Age, sex, systemic BP parameters, HR, BMI, and plasma levels of cholesterol and TGs did not have any influence on either MPOD or glutathione levels (all P > 0.05). In addition, a forward stepwise multiple regression analysis showed MPOD to have a significantly and independent correlation with GSH levels (ß = 0.63; P < 0.001). Conclusions. In otherwise healthy older individuals, there is a positive correlation between local and systemic antioxidant defense mechanisms.

Relationships between beta-amyloid (A beta) deposits and blood vessels in patients with sporadic and familial Alzheimer's disease

The density of diffuse, primitive and classic beta-amyloid (A beta) deposits was studied in relation to the incidence of blood vessels in the superior frontal gyrus of nine cases of sporadic Alzheimer's disease (SAD), two cases of familial Alzheimer's disease (FAD) with amyloid precursor protein (APP) mutations (APP717, Val --> Ile), and eight cases of FAD not linked to chromosomes 21, 14 or 1. Stepwise multiple regression was used to determine for each patient whether variations in the density of A beta deposits along the cortex were significantly correlated with the incidence of blood vessels. In the majority of FAD and SAD cases, the density of the diffuse and primitive type A beta deposits was not related to blood vessels. However, the incidence of the larger diameter (> 10 microns) blood vessels was positively correlated with the density of the classic A beta deposits in eight (89%) SAD and two (20%) FAD cases. The data suggest that the densities of vessels and deposits were not significantly correlated between cases but only within cases, suggesting a strictly local effect. In addition, the spatial association between classic A beta deposits and blood vessels may be more apparent in SAD compared with FAD cases.

Alzheimer's disease: the relationship between the density of senile plaques, neurofibrillary tangles and A4 protein in human patients

The numerical density of senile plaques (SP) and neurofibrillary tangles (NFT) as revealed by the Glees silver method was compared with SP and NFT revealed by the Gallyas method and with amyloid (A4) deposits in immunostained sections in 6 elderly cases of Alzheimer's disease. The density of NFT was generally greater and A4 lower in tissue from hippocampus compared with the neocortex suggesting that A4 deposition was less important than the degree of paired helical filament (PHF) related damage in the hippocampus. The density of Glees SP was positively correlated Gallyas SP weakly correlated with A4 deposit number. A stepwise multiple regression analysis which included A4 deposit and Gallyas SP density and accounted for 54% of the variation in Glees SP density. Hence, different populations of SP were revealed by the different staining methods. The results suggested that the Glees method may stain a population of SP in a region of cortex where both amyloid deposition and neurofibrillary changes have occurred.

Measuring the degree of spatial correlation between pathological lesions in Alzheimer's disease

The pathological lesions characteristic of Alzheimer's disease (AD), viz., senile plaques (SP) and neurofibrillary tangles (NFT) may not be randomly distributed with reference to each other but exhibit a degree of sptial association or correlation, information on the degree of association between SP and NFT or between the lesions and normal histological features, such as neuronal perikarya and blood vessels, may be valuable in elucidating the pathogenesis of AD. This article reviews the statistical methods available for studying the degree of spatial association in histological sections of AD tissue. These include tests of interspecific association between two or more histological features using chi-square contingency tables, measurement of 'complete' and 'absolute' association, and more complex methods that use grids of contiguous samples. In addition, analyses of association using correlation matrices and stepwise multiple regression methods are described. The advantages and limitations of each method are reviewed and possible future developments discussed.

The levels of ribitol, arabitol and mannitol in individual lobes of the lichen Parmelia conspersa (Ehrh. ex Ach.) ACH.

The levels of the soluble carbohydrates ribitol, arabitol and mannitol were measured in individual lobes of the lichen Parmelia conspersa (Ehrh. ex Ach.) Ach. Lobes were collected from a north and a south facing slate rock surface in South Gwynedd, Wales, U.K. on 4 days during 1990-1991. On each day sampled, the most significant variation in soluble carbohydrate levels was between the individual lobes of a thallus. In addition, carbohydrate levels were significantly greater on the south facing rock surface on 2 of the 4 days sampled. Factorial analyses of variance suggested that the levels of individual carbohydrates varied significantly between days but not between north and south facing rock surfaces. Mannitol levels varied less between days than arabitol levels. Levels of ribitol, arabitol and mannitol were positively correlated in individual lobes. A stepwise multiple regression suggested that on the north facing rock surface, arabitol and mannitol levels could be explained by variations in the level of ribitol. By contrast, on the south facing rock surface, the levels of fungal carbohydrates were less dependent on the level of ribitol and there was evidence of a relationship between arabitol and mannitol. Variations in carbohydrate production, allocation and metabolism could help to explain lobe growth variation in foliose lichens and the radial growth of lobes over a longer period of time. Greater carbohydrate production rather than differences in allocation and metabolism may explain the increased growth and frequency of P. conspersa on south facing rock surfaces in South Gwynedd. © 1994.

Alzheimer's disease: Are cellular neurofibrillary tangles linked to beta/A4 formation at the projection sites?

The density of senile plaques (SP) and cellular neurofibrillary tabgles (NFT) revealed by the Glees and Gallyas stains; and beta/A4 deposits revealed by immunocytochemical staining, was estimated in the hippocampus and adjacent gyri in Alzheimer's disease (AD). Stepwise multiple regression was used to detemine whether the density of cellular NFT was related to the density of SP or beta/A4 deposits totalled over the projection sites. Cellular NFT density was only weakly correlated with the density of Glees SP and beta/A4 deposits at some of the projection sites. However, beta/A4 deposit density in a tissue was strongly correlated with the density of beta/A4 deposits at the projection sites suggesting that the lesions could spread through the brain. Hence, although there is a strong correlation between the density of beta/A4 deposits in different parts of the hippocampal formation there is little association between SP or beta/A4 and cellular NFT. These results do not provide strong evidence that beta/A4 protein is the cause of the neuritc changes in AD.

The influence of climate on the dispersal of lichen soredia

The relationship between the daily deposition of soredia of Hypogymnia physodes (L.) Nyl. and local climatic records was studied in the field during three periods at a site in Seattle, WA, U.S.A: (1) 11 August – 16 September 1986 (Study A); (2) 16 December – 11 January 1987 (Study B) and (3) 8 July 1988 – 30 January 1989 (Study C). The soredia were trapped on adhesive strips placed at various locations on a Prunus blireiana L. tree for 24 hr periods. A correlation matrix of the data from all three studies revealed a negative correlation between soredial deposition and relative humidity; and a positive correlation with rainfall and temperature. A multiple regression and forward stepwise regression analysis selected relative humidity as the most significant climatic variable, i.e. more soredia tended to be deposited when relative humidity was low. Analysis of individual studies by multiple regression revealed: (1) no significant relationships between soredial deposition and climate in Study A; (2) positive relationships with temperature and wind speed in Study B and (3) positive relationships with wind speed and rainfall in the summer/autumn months of Study C; in the winter months no relationships with climate were found because few soredia were deposited. The data suggest that in the field seasonal photoperiod differences combined with moderately high temperatures and high relative humidity may promote soredial formation and accumulation on thalli prior to soredia dispersal. In addition, low relative humidity may promote soredial release while wind and raindrops may be possible agents of dispersal.

Spatially orthogonal chemical functionalization of a hierarchical pore network for catalytic cascade reactions

The chemical functionality within porous architectures dictates their performance as heterogeneous catalysts; however, synthetic routes to control the spatial distribution of individual functions within porous solids are limited. Here we report the fabrication of spatially orthogonal bifunctional porous catalysts, through the stepwise template removal and chemical functionalization of an interconnected silica framework. Selective removal of polystyrene nanosphere templates from a lyotropic liquid crystal-templated silica sol–gel matrix, followed by extraction of the liquid crystal template, affords a hierarchical macroporous–mesoporous architecture. Decoupling of the individual template extractions allows independent functionalization of macropore and mesopore networks on the basis of chemical and/or size specificity. Spatial compartmentalization of, and directed molecular transport between, chemical functionalities affords control over the reaction sequence in catalytic cascades; herein illustrated by the Pd/Pt-catalysed oxidation of cinnamyl alcohol to cinnamic acid. We anticipate that our methodology will prompt further design of multifunctional materials comprising spatially compartmentalized functions.

Predicting changes in measured introcular pressure with non-contact tonometry after LASIK

Purpose: Optometrists are becoming more integrally involved in the diagnosis of and care for glaucoma patients in the UK. The correlation of apparent change in non contact tonometry (NCT) IOP measurement and change in other ocular parameters such as refractive error, corneal curvature, corneal thickness and treatment zone size (data available to optometrists after LASIK) would facilitate care of these patients. Setting: A UK Laser Eye Clinic. Methods: This is a retrospective study study of 200 sequential eyes with myopia with or without astigmatism which underwent LASIK using a Hansatome and an Alcon LADARvision 4000 excimer laser. Refraction keratometry, pachymetry and NCT IOP mesurements were taken before treatmebnt and agian 3 months after treatment. The relationship between these variables anfd teh treatment zones were studied using stepwise multiple regression analysis. Results: There was a mean difference of 5.54mmHg comnparing pre and postoperative NCT IOP. IOP change correlates with refractive error change (P < 0.001), preoperative corneal thickness (P < 0.001) and treatment zone size (P = 0.047). Preoperative corneal thickness correlates with preoperative IOP (P < 0.001) and postoperative IOP (P < 0.001). Using these correlations, the measured difference in NCT IIOP can be predicted preoperatively or postoperatively using derived equations.Conclusion: There is a significant reduction in measured NCT IOP after LASIK. The amount of reduction can be calculated using data acquired by optometrists. This is helpful for opthalmologists and optometrists who co-manage glaucoma patients who have had LASIK or with glaucoma pateints who are consideraing having LASIK.

Studies in clay chemistry

A study of clay chemistry has been approached with three aims: - to modify the conducting properties by intercalation of tetrathiafulvalene, - to study the electrochemistry of redox-active coordination compounds immobilised on clay coated electrodes, and - to study the role of clays as reagents in inorganic glass forming reactions using mainly solid-state magic-angle-spinning NMR. TTF was intercalated by smectites containing different interlayer and lattice cations. Evidence from ESR and 57Fe Mossbauer indicated charge-transfer from TTF to structural iron in natural montmorillonite, and to interlayer Cu2+ in Cu2+ exchanged laponite. No charge transfer was observed for laponite (Na+ form) itself. Ion exchange of TTF3(BF4)2 with laponite was found to proceed quantitatively. The intercalated species were believed to be (TTF)2+ dimers. Conductivity data showed an order of magnitude increase for the intercalated clays. The mechanism is thought to be ionic rather than CT as Na+ laponite showed a similar enhancement in conductivity. Mechanically robust colloidal clay films were prepared on platinum electrodes. After immersion in solutions containing redox active complexes [Co(bpy)3]3+ and [Cr(bpy)3]3+, the films became electroactive when a potential was applied. Cyclic voltammograms obtained for both complexes were found to be of the diffusion controlled type. For [Co(bpy)3]3+ immobilised on clay coated electrodes, a one-step oxidation and four-step reduction wave was observed corresponding to a one electron stepwise reversible reduction of Co(III), through Co(II), Co(I), Co(O) to Co(I) oxidation state. For [Cr(bpy)3]3+ the electrochemistry was complicated by the presence of additional waves corresponding to the dissociation of [Cr(bpy)3]3+ into the diaquo complex. ESR and diffuse reflectance data supported such a mechanism. 29Si, 27Al and 23Na MAS NMR spectroscopy, supported by powder XRD and FTIR, was used to probe the role of clays as reagents in glass forming reactions. 29Si MAS NMR was found to be a very sensitive technique for identifying the presence and relative abundance of crystalline and non-crystalline phases. In thermal reactions of laponite formation of new mineral phases such as forsterite, akermanite, sillimanite and diopside were detected. The relative abundance of each phase was dependent on thermal history, chemical nature and concentration of the modifier oxide present. In continuing work, the effect of selected oxides on the glass forming reactions of a model feldspar composition was investigated using solid state NMR alone. Addition of network modifying oxides generally produced less negative 29Si chemical shifts and larger linewidths corresponding to a wider distribution of Si-O-Si bond angles and lengths, and a dominant aluminosilicate phase with a less polymerised structure than the starting material. 29Si linewidths and 27Al chemical shifts were respectively correlated with cationic potential and Lewis acidity of the oxide cations. Anomalous Al(4) chemical shifts were thought to be due to precipitation of aluminate phases rather than a breakdown in Lowenstein's aluminium avoidance principle.

The analysis of organic matter in oil-shales

The organic matter in five oil shales (three from the Kimmeridge Clay sequence, one from the Oxford Clay sequence and one from the Julia Creek deposits in Australia) has been isolated by acid demineralisation, separated into kerogens and bitumens by solvent extraction and then characterised in some detail by chromatographic, spectroscopic and degradative techniques. Kerogens cannot be characterised as easily as bitumens because of their insolubility, and hence before any detailed molecular information can be obtained from them they must be degraded into lower molecular weight, more soluble components. Unfortunately, the determination of kerogen structures has all too often involved degradations that were far too harsh and which lead to destruction of much of the structural information. For this reason a number of milder more selective degradative procedures have been tested and used to probe the structure of kerogens. These are: 1. Lithium aluminium hydride reduction. - This procedure is commonly used to remove pyrite from kerogens and it may also increase their solubility by reduction of labile functional groups. Although reduction of the kerogens was confirmed, increases in solubility were correlated with pyrite content and not kerogen reduction. 2. O-methylation in the presence of a phase transfer catalyst. - By the removal of hydrogen bond interactions via O-methylation, it was possible to determine the contribution of such secondary interactions to the insolubility of the kerogens. Problems were encountered with the use of the phase transfer catalyst. 3. Stepwise alkaline potassium permanganate oxidation. - Significant kerogen dissolution was achieved using this procedure but uncontrolled oxidation of initial oxidation products proved to be a problem. A comparison with the peroxytrifluoroaceticacid oxidation of these kerogens was made. 4. Peroxytrifluoroacetic acid oxidation. - This was used because it preferentially degrades aromatic rings whilst leaving any benzylic positions intact. Considerable conversion of the kerogens into soluble products was achieved with this procedure. At all stages of degradation the products were fully characterised where possible using a variety of techniques including elemental analysis, solution state 1H and 13C nuclear magnetic resonance, solid state 13C nuclear magnetic resonance, gel-permeationchromatography, gas chromatography-mass spectroscopy, fourier transform infra-red spectroscopy and some ultra violet-visible spectroscopy.