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Biomedical subjects

B J Evans

Publications and source records attributed to B J Evans.

At least 37 records · Page 2Linked to original sources
PubMed1995

A new protocol for the optometric management of patients with reading difficulties.

Research by Evans et al. (Ophthal. Physiol. Opt. 15, 481-487, 1995) has demonstrated a correlation between visual processing and ocular motor factors in people with specific reading difficulties (dyslexia). In addition, research by Wilkins et al. (Ophthal. Physiol. Opt. 14, 365-370, 1994) has shown that some people with dyslexia will benefit from a reduction of perceptual symptoms of discomfort and distortion if they use individually prescribed coloured filters. Three examples of the dyslexic patients who attend at the Institute of Optometry clearly demonstrate the importance of full investigation of ocular function, including the assessment of the effect of colour on visual perception. All three patients presented with similar symptoms of asthenopia when reading. Symptoms were alleviated for the first patient by use of orthoptic treatment of an exotropia with intermittent suppression. With the second patient, ocular motor functions were found to be within acceptable limits and relief of symptoms was obtained by the prescribing of lenses of a specific chromaticity. For the third patient, both orthoptic intervention and the use of specifically tinted lenses were necessary to relieve the visual difficulties that were being experienced. By taking advantage of recent research and developments in optometric instrumentation, it is possible for some of those with dyslexia to receive considerable benefit from optometric intervention.

Adolescent↗
PubMed1995

Is there a visual deficit in dyslexia resulting from a lesion of the right posterior parietal lobe?

Dyslexia has conventionally been attributed to a left hemisphere deficit affecting language skills. However, it has recently been suggested that two-thirds of dyslexic people have a lesion of the right posterior parietal lobe (RPPL) resulting in poor oculo-motor control. It has been reported that neurological patients with RPPL lesions commonly manifest a neglect of the left side of space and this has also been described in clinical observations of 'visual dyslexics'. We investigated this hypothesis with a sample of 53 dyslexic children and 53 controls using a line-bisection task. In the horizontal test condition both groups tended to transect slightly to the left of the midpoint (mean displacement 0.14 mm for controls; 0.4 mm for dyslexics). The result suggests a small right side neglect which, contrary to one report in the literature, is found here in developmental dyslexics as well as controls, and leads to the conclusion that RPPL lesion is unlikely to be a common feature of dyslexia.

Adolescent↗
PubMed1994

An investigation of some sensory and refractive visual factors in dyslexia.

The role of visual factors in dyslexia has been a long-standing source of controversy. Recent research has suggested that there may be a deficit of the transient visual subsystem in dyslexia. The evidence for this hypothesis comes principally from investigations of spatial and temporal contrast sensitivity and visual persistence. This evidence is reviewed and it is noted that previous work has never applied two of these purported "tests of transient function" to the same subject group. The hypothesised transient system deficit in dyslexia was investigated in a study comparing 43 control with 39 dyslexic children who were matched for age, sex, and intelligence. Comprehensive psychometric and optometric data were obtained, including visual acuities and refractive errors. The spatial contrast sensitivity function was determined in such a way as to investigate further the findings of Lovegrove, Martin, Bowling, Blackwood, Badcock and Paxton [(1982) Neuropsychology, 20, 309-315] and Martin and Lovegrove [(1984) Neuropsychologia, 22, 73-77]. It might be expected, from the work of Merigan and Maunsell [(1990) Neuroscience, 5, 347-352], that a better test of magno-cellular function would be to investigate the modulation threshold for a virtually uniform field that was flickering sinusoidally at 10 Hz. This temporal contrast sensitivity was studied in a similar way to Brannan and Williams [(1988) Clinical Vision Sciences, 3, 137-142]. A non-verbal simulated reading visual search task was used to investigate the effect of any visual deficits on a test that was, in its low-level visual requirements, similar to reading. The following factors were found to be significantly associated with dyslexia: reduced visual acuity, impaired flicker detection at 10 Hz, reduced low spatial frequency contrast sensitivity, and slightly slower performance at a simulated reading visual search task. The two alleged "tests of transient function" were only weakly correlated with one another (r = 0.183), suggesting that these variables do not measure the same function. Much of the dyslexic group's slightly slower performance at the simulated reading task could be accounted for by the psychometric variable of visual sequential memory. Like reading, the simulated reading task requires the accurate perception of sequential characters. Hence, it seems unlikely that the low-level visual deficits in the dyslexic group were major causes of their poor reading performance. Alternative explanations for the results are discussed.

Child↗
PubMed1994

Functional characteristics of small placental arteries.

OBJECTIVES: The aim of this study was to investigate characteristics of placental arteries capable of influencing vasomotor tone in the fetoplacental vascular bed. Contractile characteristics and endothelium-dependent and endothelium-independent relaxation were examined. STUDY DESIGN: By means of a small vessel myograph arteries of mean normalized internal diameter 353.22 +/- 13.14 microns were studied under isometric conditions. Contractile function was assessed with a variety of agonists, including angiotensin II, endothelin-1, the thromboxane mimetic U46619, prostaglandin E2, and prostaglandin F2 alpha. The effect of physiologic and supraphysiologic PO2 on vascular function was also examined. Relaxation was assessed in response to known endothelium-dependent vasodilators, including acetylcholine, bradykinin, histamine, and A23187 and to sodium nitroprusside (endothelium independent). The effect of indomethacin and the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester on contractile function was also evaluated. RESULTS: Sensitivity to sodium nitroprusside was reduced by a high PO2. U46619 was the most potent constrictor agonist studied. The response of precontracted arteries to known endothelium-dependent vasodilators was minimal, other than for histamine, which led to modest relaxation. The constrictor response to U46619 was increased in the presence of NG-nitro-L-arginine methyl ester. CONCLUSIONS: Oxygen tension may be an important determinant of relaxation in small placental arteries. Receptor-mediated release of endothelium-derived relaxing factor is not a major mechanism in the fetoplacental circulation.

Arteries↗
PubMed1994

Videokeratographic evaluation of peripheral redeepening in the cadaver eye.

Radial incisions must be deep enough to correct myopia. As currently performed, most surgeons set their diamond blades at a constant depth and do not alter the blade length throughout the procedure. The cornea is not uniformly thick; the central cornea is the thinnest and it thickens toward the periphery. Therefore, an incision of constant depth would be deeper centrally and thinner peripherally. Peripheral redeepening of the cornea would in theory make the incision depth deeper throughout and should increase the effect of radial incisions. We reviewed the literature on this technique and performed radial incisional studies on the human cadaver eye using videokeratography to measure incision depth indirectly. Based on our studies, we believe that peripheral redeepening has no effect on central cornea flattening.

Cadaver↗
PubMed1994

Effect of pattern glare and colored overlays on a stimulated-reading task in dyslexics and normal readers.

Scotopic sensitivity syndrome or the Irlen syndrome describes symptoms of asthenopia anamolous visual performance experienced while reading that are lessened by colored filters. One putative explantation for this condition relates to pattern glare: a hypersensitivity to repetitive patterns, including lines of print on a page. Experiment 1 used a placebo-controlled paradigm to investigate the effect of pattern glare and colored overlays on performance at a simulated reading visual search task. Despite the fact that the subjects were university students, the results showed a tendency, of border-line significance, to support the conclusion that colored filters seem to improve reading through ameliorating pattern glare. In experiment 2 we compared the prevalence of pattern glare in matched groups of dyslexic children and good readers. The dyslexic group reported more pattern glare, but also reported more glare from a control stimulus. Pattern glare in the dyslexic group was directly correlated with flicker sensitivity. The results are related to recent research on visual processing and ocular-motor function in dyslexia.

Adult↗
PubMed1994

Investigation of accommodative and binocular function in dyslexia.

The visual correlates of dyslexia are the subject of controversy, and much evidence suggests that they may include some aspects of binocular and accommodative function. These factors were investigated in 43 control and 39 dyslexic children, who were matched for age, sex and performance intelligence quotient. The dyslexic group exhibited significantly lower positive and negative vergence reserves, and vergence instability when the eyes were dissociated at near. Their amplitudes of accommodation also were significantly reduced. However, other measures including dissociated and associated heterophoria and accommodative lag and facility were similar in both groups. The stability of motor ocular dominance, as assessed with a modified Dunlop test, was similar in both groups. The results of a simulated reading visual search task suggested that the vergence and accommodative dysfunction were not a major cause of the dyslexia. Further analyses, using reading-age matched groups, suggested that these ocular motor correlates were not attributable to the better reading performance in the control group. The most likely remaining explanation is that they are, in most cases, non-causal correlates of the dyslexia.

Accommodation, Ocular↗
PubMed1994

Double-masked placebo-controlled trial of precision spectral filters in children who use coloured overlays.

We selected 68 children who reported benefit from individually chosen sheets of coloured plastic placed upon the page when reading, and who used these regularly without prompting. These children viewed text illuminated by coloured light in an apparatus that allowed the separate manipulation of hue (colour) and saturation (depth of colour), at constant luminance. Many of the children reported improvements in perception when the light had a chromaticity within a limited range, which was different for each individual. A pair of plastic spectacle lenses ('experimental' lenses) was dyed so as to provide the appropriate chromaticity under conventional white (F3) fluorescent light. An additional pair was prepared having very similar colour but with a chromaticity outside the range in which perception was reported to improve ('control' lenses). Each pair was provided for 1 month in random order. The children kept diaries (36 completed) recording symptoms of eye-strain and headache. The children and those responsible for their assessment were unable reliably to distinguish 'experimental' from 'control' lenses. Nevertheless, symptoms were less frequent on days when the 'experimental' lenses were worn (P < 0.003).

Adolescent↗
PubMed1993

Behavioural assessment of the effectiveness of a communication programme for medical students.

This study evaluated the effectiveness of a communication programme taught to medical students at the University of Melbourne in their preclinical years. The effectiveness of the programme was assessed by comparing videotaped history-taking interviews completed by a cohort of first-year clinical students in 1986, who had not undertaken the communication programme, with a similar cohort of first-year clinical students in 1992 who had undertaken the programme. The students from the 1986 cohort who had not undertaken communication training in their preclinical course completed their videotaped interviews as part of the experimental evaluation of a consulting skills training programme carried out in 1986-87. A comparison of ratings given by two experimentally naive, independent observers revealed that the 1992 student cohort demonstrated some significantly better skills at questioning and facilitating communication with patients. By contrast, the 1986 student cohort showed significantly greater skills at maintaining relevance in their interviews and greater capacity to explore patients' psychosocial concerns. These data suggest that students acquire the most effective interview skills when interacting with patients during their clinical training.

Australia↗
PubMed1993

Measuring medical students' empathy skills.

Empathy is an important skill for the medical practitioner or medical students to develop when interviewing patients. It helps the interviewer establish effective communication, which is important for accurate diagnosis and patient management. Two facets of medical education limit students' development of accurate empathy: the traditional format of interviewing training and the social ethos of medical training and medical practice, which stress clinical detachment. A number of researchers and educators have developed consulting skills training programmes, designed to enhance students' empathic skills and ability. One difficulty for researchers has been the conceptual complexity of the term 'empathy' and greater difficulty in measuring the dimension. This paper reviews the range of approaches to the measurement of empathy and reports on a research study designed to evaluate a two-stage measurement technique, involving a pencil-and-paper test of empathy and independent observer ratings of medical students' actual interview behaviours. Results lead to the conclusion that pencil-and-paper tests of empathy cannot incorporate the range of complex cognitive, emotional and behavioural components of the empathy construct. On the other hand, trained observers have been able to use items on a specially developed History-taking Rating Scale to discriminate between the empathic behaviours of a group of students trained in consulting skills with those of a group of control students who each carried out videotaped history-taking interviews with hospitalized patients.

Adult↗
PubMed1992

Neuropathology of the chronic epileptic syndrome induced by intrahippocampal tetanus toxin in rat: preservation of pyramidal cells and incidence of dark cells.

A few nanograms of tetanus toxin injected into a rat hippocampus causes a chronic epileptic syndrome characterized by brief seizures that recur intermittently for about 6 weeks. Cognitive and other behavioural impairments persist after the seizures and other epileptic electrographic activity have remitted, and may be permanent. Our previous studies suggested that the behavioural changes following seizure remission were an indication of functional impairment associated with decreased neuronal excitability rather than with neuronal loss. The conclusion that neurons were preserved relied on qualitative histological observations and, indirectly, on electrophysiological measurements of the amplitudes of antidromic population spikes. Recently, gross histopathology has been described in a quantitative histological study of rats 7-10 days after they had received rather higher doses of intrahippocampal tetanus toxin. Here we report a quantitative histological study of hippocampi from rats which had gained remission from seizures induced by low doses of tetanus toxin. Adult Sprague Dawley rats received unilateral injections of 3-4 ng (about 6-8 mouse LD50) tetanus toxin, or vehicle, into the dorsal hippocampus. The first experiment confirmed that postsynaptic evoked responses recorded from pyramidal cells were depressed 10-19 weeks after injection. Unexpectedly, there also was a decrease of 20% in the antidromic response from CA3a contralateral to the injection. However, cell counts in these hippocampi revealed no change in pyramidal cell numbers. The second experiment used rats from two breeding colonies, prepared for histology 7 weeks after injection. Hippocampal pyramidal cell numbers were within the normal range in all but three of the 24 rats that had received tetanus toxin. These three had lesions of the CA1 pyramidal layer contralateral to the injection. The lesions were of the order of 2 mm in diameter, and were associated with glial proliferation. When these three cases were excluded, there remained a small increase in glial density in CA1 of the toxin-injected rats. In addition, toxin-injected rats from one of the colonies were susceptible to a pathology known as acidophylic or dark cell change. These occurred in 11 of 18 toxin-injected rats from this colony, in all divisions of the pyramidal layer, in both the injected and the contralateral hippocampus (where parallel studies revealed independent secondary epileptic foci). We conclude that loss of pyramidal neurons is not necessary for the persistent behavioural changes in this model.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Effects of communication skills training on students' diagnostic efficiency.

This study evaluates the impact of a training programme in communications skills on subsequent diagnostic efficiency. Videotaped history-taking interviews conducted by groups of specially trained and control groups of students were rated for their diagnostic efficiency by two medical practitioners. Students in the trained group had shown greatly increased skills in interviewing and interpersonal effectiveness as a result of their training. A comparison of ratings given by the two experimentally naive, independent observers revealed that trained students were significantly better at eliciting full, relevant data from patients--they were diagnostically more efficient, but took no longer than their control group counterparts to elicit the information. Further research with the medical interview rating scale will clarify the skills required of medical students in interviewing and diagnosis and facilitate remedial training for students who show poor interview skills.

Clinical Competence↗
PubMed1991

Tinted lenses and related therapies for learning disabilities--a review.

Research relating to the use of Irlen tinted lenses and coloured overlays for underachievers is reviewed. Many of the studies were not published in refereed journals and were methodologically poor. The weaknesses of the Irlen argument are discussed, including the absence of evidence to support the claims that these tints need to be uniquely prescribed and manufactured. Syntonics is another form of visual colour therapy that has been applied to those with a learning disability. Research on this is reviewed, and is also shown to have procedural irregularities which preclude firm conclusions. Owing to the poor quality of much of this research the claims of the protagonists of these therapies cannot be proved or disproved. A proposed new therapy is normally preceded by a valid theoretical hypothesis; this has been lacking in the present topic. Recently, a feasible explanation has been proposed in terms of 'pattern glare' resulting from mild hypersensitivity to epileptogenic patterns. This, together with potential alternative theories, is discussed. In the conclusion of this review, advice is given for eye-care practitioners who may be consulted on these therapies.

Adolescent↗
PubMed1990

Review of ophthalmic factors in dyslexia.

Dyslexia and the effect of visual problems on reading ability have long been subjects of controversy. This paper critically reviews the literature on the relationship between reading disability and visual acuity, refractive error, binocular vision anomalies, eye movements, ocular pathology and the transient and sustained visual systems. The limitations of much of the work in this field are described, with particular reference to the problems of subject selection and group matching. Tentative conclusions, with deference to the complex nature of dyslexia, are drawn and suggestions are made for future research.

Accommodation, Ocular↗
PubMed1989

Lectures and skills workshops as teaching formats in a history-taking skills course for medical students.

The consulting skills acquired by medical students during their training are an important determinant of their ability to conduct adequate and efficient clinical interviews. These skills comprise: the acquisition of medical knowledge and the ability to apply this; and communication skills required to obtain full, accurate clinical histories from patients and to be able to give to patients the information they need to comply with prescribed regimens. Until recently, consulting skills training has certainly not had a high profile in medical curricula, despite evidence that students do not gain sufficient expertise during their medical training. A history-taking skills course within the Austin Hospital Clinical School, utilizing mass lecture and small-group skills workshops is described. Independent evaluation of students' videotaped interviews with patients, completed before training, after mass lectures and following small-group workshops, showed that students trained in consulting skills demonstrated significant improvements in interview skills and techniques, compared with a similar group of students for whom training followed the more traditional model. Whilst there were some improvements after mass lectures, most significant gains in history-taking skills were obtained following skills workshops. Ongoing evaluation of these students will determine if these short-term improvements in consultation skills persist over their clinical training and internship.

Clinical Clerkship↗
PubMed1989

Psychological tests to measure the effects of medical education on students' interpersonal skills.

The consulting skills required of medical students and practitioners have been categorized into a number of specific skills, two of which are: students' ability to empathize with the patient; and ability to decode non-verbal cues given by the patient in the interview. Training programmes to improve students' consulting skills are usually evaluated using analysis of students' actual interview behaviours with patients. Broad psychological and personality tests have also been used to measure changes in students' interviewing skills, but have generally not been successful. The hypothesis is advanced that more specific tests of the skills of interviewing, such as non-verbal sensitivity and empathy, would detect changes in students' ability to display these skills. As part evaluation of a consulting skills training programme, clinical students completed psychological tests of empathy and non-verbal sensitivity. Subsequent comparisons between trained and control student groups revealed no clear pattern in test results. These data suggest that specific psychological tests of empathy and non-verbal sensitivity may be no more effective in detecting changes in students' interpersonal skills than global personality measures.

Clinical Clerkship↗