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Biomedical subjects

P Mitchell

Publications and source records attributed to P Mitchell.

At least 307 records · Page 17Linked to original sources
PubMed1997

Lack of association between localized cataract and visual field loss: the Blue Mountains Eye Study.

PURPOSE: To examine whether localized cataract is related to localized field defects on suprathreshold visual field testing. METHODS: Suprathreshold screening visual fields (Humphrey 76-point test) and lens photographs, graded using the Wisconsin System, were performed on participants attending the Blue Mountains Eye Study, which examined 3654 subjects residing in an area west of Sydney, NSW, Australia. The results for 2276 subjects were analysed in the present study. RESULTS: There were no significant relationships between total points missing in the visual field and the degree of cortical, posterior subcapsular (PSC) or nuclear cataract after adjusting for confounders (test for trend P = 0.9, 0.7 and 0.9, respectively). Adjusted prevalence ratios and 95% confidence limits for the association between 10 or more points missing and the presence of cataract were 0.94 (0.77-1.25) for cortical, 1.26 (0.82-1.93) for PSC and 1.06 (0.86-1.30) for nuclear cataract. Similarly, there was no relationship between the presence of cortical or PSC cataract and sectoral visual field loss in any quadrant or hemifield. CONCLUSIONS: Neither cortical, nuclear nor PSC cataracts increase the total points missing on the 76-point suprathreshold field test. Similarly, neither cortical nor PSC cataracts cause sectoral visual field loss on this screening field test. In the presence of cataract, sectoral visual field loss on non-thresholding visual field screeners must be attributed to other causes, such as glaucoma. The present study provides a clinical alert that localized field loss is unlikely to be related to cataract.

Aged↗
PubMed1997

Traumatic retinopathy resembling acute macular neuroretinopathy.

BACKGROUND: Acute macular neuroretinopathy (AMNR) is an uncommon disease of uncertain aetiology. We report on four males who developed unilateral changes following trauma which closely resembled acute macular retinopathy. METHODS: Retrospective review of selected cases. RESULTS: Four male patients developed a central or paracentral scotoma immediately or soon after an accident in which they suffered moderately severe bodily injury without direct ocular trauma. Vision was reduced in three patients. All four patients had characteristic well-circumscribed, dark macular lesions best seen using red-free light. The lesions cleared slowly in the two cases who returned for review. CONCLUSIONS: A picture that closely resembles AMNR may be seen after trauma. The mechanism may involve a sudden rise in ocular venous pressure. This may be an unrecognized cause of visual loss after non-ocular trauma which may be regarded as functional. The subtle retinal lesions may be overlooked unless the fundi are examined in red-free light and the macular dark areas are compared.

Acute Disease↗
PubMed1997

Acute posterior multifocal placoid pigment epitheliopathy: a long-term study.

PURPOSE: To study the long-term visual outcome in patients with acute posterior multifocal placoid pigment epitheliopathy (APMPPE). METHODS: Fifteen patients (28 eyes) with APMPPE were reassessed at Westmead Hospital Eye Clinic (Westmead, NSW, Australia) up to 18 years (mean 6.4 years) after their initial presentation to one of the authors (PM) or to their private ophthalmologist. Stereo retinal photographs and visual acuities taken at the initial presentation were compared with those obtained at the most recent follow-up visit. RESULTS: The last recorded visual acuity was 6/6 or better in 16 eyes (57%), 6/9-6/18 in four eyes (14%), 6/24-6/60 in five eyes (18%) and worse than 6/60 in three eyes (11%). Nine patients (60%) were treated with oral prednisone during the acute episode with little therapeutic effect observed. Six patients (40%) described a prodromal flu-like illness. CONCLUSION: This study suggests that the long-term visual outcome following an acute episode of APMPPE may not be as favourable as initially portrayed by Gass. It confirms other study findings suggesting that APMPPE may not be a benign self-limiting disease. Older age at onset and initial foveal involvement were associated with a worse visual outcome.

Acute Disease↗
PubMed1997

Knowledge and beliefs about common eye diseases.

PURPOSE: To ascertain the level of knowledge of common causes of blindness in an adult Australian population and to relate this to use of eye care services. METHODS: A population-based study of common eye diseases in an urban population aged 49 years or older was conducted. The questions were concerned with the awareness and knowledge of and the ability to describe three common eye diseases, namely cataract, glaucoma and age-related macular degeneration (AMD). RESULTS: Awareness of cataract (98%) and glaucoma (93%) were high in this population, but awareness of AMD was low (20%). Among people who were aware of the target eye disease, only 29% showed some knowledge of glaucoma, 26% showed some knowledge of AMD and 20% showed some knowledge of cataract; this was also low in people who had previous eye treatment, such as cataract surgery. Knowledge was related to education level, occupational prestige and knowledge of other eye diseases. After excluding people with a previous eye disease diagnosis, those people who were aware and had some knowledge of eye disease accessed eyecare services more frequently. CONCLUSIONS: Knowledge of common eye diseases is generally lacking. Age-related macular degeneration is the leading cause of blindness in Australia, yet only 20% of the present study population had heard of it. As there are often no early symptoms for glaucoma, community awareness of this disease and the need for screening of people at risk may allow timely diagnosis and more effective therapy before advanced visual field loss has occurred. An informed public is more likely to present earlier with visual symptoms before irreversible visual loss has occurred and is more likely to comply better with recommended therapy.

Adult↗
PubMed1997

Gender, oestrogen, hormone replacement and age-related macular degeneration: results from the Blue Mountains Eye Study.

PURPOSE: To determine whether females have a higher age-specific age-related maculopathy prevalence than males; whether there is an increased risk of age-related macular degeneration (AMD) with early menopause; and whether there is a decreased risk of AMD with use of hormone replacement therapy (HRT). METHODS: Pooled data from three study populations that have used similar AMD diagnostic criteria were used to answer the first hypothesis: the Beaver Dam Eye Study (BDES), the Rotterdam study of the elderly, and the Blue Mountains Eye Study (BMES). The BMES population was used to answer the second and third hypotheses. This population included residents aged 49 or older with 2072 women participating, of whom 1899 postmenopausal women answered questions about menopause, menarche and HRT. AMD was diagnosed from graded retinal photographs using modified international criteria. RESULTS: The overall pooled odds ratio (OR) for association between sex and AMD revealed a significant increase in AMD prevalence among females compared with males, adjusting for 10-year age categories, OR = 1.15 (1.10-1.21), with no significant heterogeneity between studies. A significant decrease in the odds of early AMD with increasing years from menarche to menopause was observed. CONCLUSIONS: The results suggest that females may have a higher risk of AMD. The significant decrease in early AMD with increasing years from menarche to menopause supports the concept that a shorter duration of oestrogen production may increase risk of AMD.

Aged↗
PubMed1997

Relationship between cup-disc ratio and optic disc diameter: the Blue Mountains Eye Study.

PURPOSE: To determine the effects of optic disc size on vertical cup-disc ratio in subjects free of glaucoma and other optic nerve disease. METHODS: Data were collected from 3654 people, 49 years of age of older, living in the Blue Mountains, west of Sydney (NSW, Australia). Examinations performed included subjective refraction and Zeiss colour stereo optic disc photographs. Eye and camera magnification effects were corrected. RESULTS: Mean vertical disc diameter was 1.51 mm (95% confidence interval (CI) 1.504-1.516 mm) and the mean vertical cup-disc ratio was 0.43 (95% CI 0.425-0.435). Both parameters were distributed unimodally. The cup-disc ratio was strongly associated with disc diameter. Controlling for other variables, cup-disc ratio increased 0.270 (95% CI 0.250-0.290) per mm increase in disc diameter. CONCLUSIONS: Vertical optic disc diameter and cup-disc ratio are distributed near normally in older Australians. Optic discs with larger vertical diameters have considerably greater vertical cup-disc ratios.

Anthropometry↗
PubMed1997

Selection bias from sampling frames: telephone directory and electoral roll compared with door-to-door population census: results from the Blue Mountains Eye Study.

Many Australian public health research studies use the telephone directory or the electoral roll as a sampling frame from which to draw study subjects. The sociodemographic, disease-state and risk-factor characteristics of subjects who could be recruited using only the telephone directory or only the electoral roll sampling frames were compared with the characteristics of subjects who would have been missed using only these sampling frames, respectively. In the first phase of the Blue Mountains Eye Study we interviewed and examined 2557 people aged 49 and over living in a defined postcode area, recruited from a door-to-door census. This represented a participation rate of 80.9 per cent and a response rate of 87.9 per cent. The telephone directory was searched for each subject's telephone number and the electoral roll was searched for each subject. Subject characteristics for those who were present in each of these sampling frames were compared with the characteristics of those subjects not included in the sampling frames. The telephone directory listed 2102 (82.2 per cent) of the subjects, and 115 (4.5 per cent) had no telephone connected. The electoral roll contained 2156 (84.3 per cent) of the subjects, and 141 subjects (5.5 per cent) could not be found in either the electoral roll or the telephone directory. Younger subjects, subjects who did not own their own homes and subjects born outside of Australia were significantly less likely to be included in either of these sampling frames. The telephone directory was also more likely to exclude subjects with higher occupational prestige, while the electoral roll was more likely to exclude unmarried persons and males. Researchers using the telephone directory and electoral roll to select subjects for study should be aware of the potential selection bias these sampling frames incur and need to take care when generalising their findings to the wider community.

Aged↗
PubMed1997

Overly literal interpretations of speech in autism: understanding that messages arise from minds.

Children with autism and children with Down's syndrome watched the following enactment. A protagonist put one item in location A and another in location B and then left the scene. Subsequently, the items were swapped the other way round. Finally, the protagonist (who remained ignorant of the swap) requested the item in A. The observing child participant was asked to judge (1) which item the protagonist wanted and (2) which item the protagonist put in A. Unlike children with Down's syndrome, those with autism made more errors in judging that the speaker wanted the item in B than in judging that the item the speaker put in A is now in B; children with autism wrongly tended to interpret utterances literally, and they did this significantly more frequently than children with Down's syndrome. We conclude that children with autism have a difficulty making nonliteral interpretations that cannot be explained as (1) a realist bias, (2) an inability to inhibit a prepotent response, and (3) a failure to keep track of the exchange of items.

Adolescent↗
PubMed1997

Prevalence of asymptomatic retinal emboli in an Australian urban community.

BACKGROUND AND PURPOSE: Because no population-based estimates are available for asymptomatic retinal emboli, we aimed to assess prevalence and associations of this sign in a defined older Australian urban population. METHODS: A total of 3654 persons aged 49 years or older, representing 82% of residents in an urban area west of Sydney, underwent a detailed eye examination that included medical history, stereo retinal photography, and fasting blood tests including lipids. Retinal emboli were diagnosed clinically and from photographic grading and classified as cholesterol, platelet-fibrin, or calcific in type. RESULTS: Asymptomatic retinal emboli were found in 51 participants (1.4%; 95% confidence interval [CI], 1.0% to 1.8%). The prevalence was 0.8% in persons aged < 60 years, 1.4% for those aged 60 to 69 years, 2.1% for those aged 70 to 79 years, and 1.5% for those aged 80 years or older. Men had a significantly higher prevalence (2.2%) of retinal emboli than women (0.8%, P < .001) after adjustment for age (odds ratio [OR], 2.7; 95% CI, 1.5 to 4.8). Forty-one emboli (80%) were cholesterol type, 7 (14%) were platelet-fibrin, and 3 (6%) were calcific. Significant associations were found after age-sex adjustment, with hypertension (OR, 2.2; 95% CI, 1.2 to 3.8), a combined history of vascular disease (OR, 2.4; 95% CI, 1.3 to 4.4), past vascular surgery (OR, 3.5; 95% CI, 1.4 to 8.5), and current (OR, 2.2; 95% CI, 1.1 to 4.2) or any (OR, 2.6; 95% CI, 1.2 to 4.3), smoking history. These associations persisted after multivariate analysis. There were no significant associations with diabetes, obesity, or fasting blood test findings. CONCLUSIONS: This study provides accurate prevalence rates for asymptomatic retinal emboli in the elderly and confirms associations with hypertension, smoking, and vascular disease.

Age Factors↗
PubMed1997

Pigmentary retinopathy associated with the mitochondrial DNA 3243 point mutation.

Fourteen patients from four unrelated families were studied to determine the prevalence of retinal pigmentary abnormalities associated with the MELAS A to G 3243 point mutation. Neurologic and ophthalmic examinations, retinal photography, pattern shift visual evoked potentials, and electroretinography were performed in all patients. Eight of the 14 patients had retinal pigmentary abnormalities characterized by symmetric areas of depigmentation involving predominantly the posterior pole and midperipheral retina. None of the patients had optic atrophy and only one patient with pigmentary retinal abnormalities had impaired visual acuity. None of the diabetic subjects (n = 6) had signs of diabetic retinopathy. Fluorescein angiography demonstrated mottled hyper- and hypofluorescent areas indicating multiple window defects in the retinal pigmentary epithelium. Visual evoked potentials showed delayed P100 responses in four of the eight patients with retinal pigmentary abnormalities. We conclude that there is a high prevalence of retinal pigmentary abnormalities in patients with MELAS A to G 3243 point mutation. These abnormalities are usually asymptomatic and best detected by retinal photography.

Adolescent↗
PubMed1997

Physical activity in a multiethnic population of third graders in four states.

OBJECTIVES: This research assessed the amount of daily physical activity in a multiethnic sample of US third-grade students. METHODS: Physical activity interviews were conducted with 2410 third graders from 96 schools in four states. Blood pressure, cholesterol, body mass index, timed run for distance, physical-activity self-efficacy, and perceived support for physical activity were also assessed. RESULTS: Students reported a daily average of 89.9 minutes of moderate to vigorous physical activity, 34.7 minutes of vigorous activity, and 120.4 minutes of sedentary behavior; however, 36.6% obtained less than 60 minutes of moderate to vigorous physical activity daily, and 12.8% reported less than 30 minutes. Boys reported more physical and sedentary activity than girls; White children reported more activity than Black or Hispanic children; California children reported the most activity and Louisiana children the least. Geographic location, male gender, lower cholesterol, higher perceived efficacy in physical activity, and higher social support were associated with more physical activity. CONCLUSIONS: Average reported activity met the Year 2000 objectives; however, many students reported less than recommended amounts of activity. These findings support the need for health promotion programs that increase the number of physically active children.

Analysis of Variance↗
PubMed1997

Utilising molecular biological and histopathological techniques to study the dopaminergic system in patients with melancholia.

OBJECTIVE: To describe the rationale for investigating the dopaminergic system in patients with melancholia by applying molecular biological (notably, in situ hybridisation) and histopathological techniques in postmortem brain tissue. METHOD: Relevant advances in the functional neuroanatomy of frontostriatal circuits, as well as insights from clinical neuroimaging studies in primary and secondary depressive disorders, are presented. These are integrated with developments in the pharmacological and molecular characteristics of dopamine receptor subtypes and recognition of their selective anatomical distribution. RESULTS: Converging data from the basic and clinical neurosciences suggest that the pathophysiology of depressive disorders characterised by psychomotor phenomena, such as melancholia, may involve dysregulation of dopaminergic mechanisms within complex frontostriatal circuits. CONCLUSIONS: The key feature of in situ hybridisation is its capacity to test for variations in the functional components of designated biochemical systems within highly specific anatomical regions. We utilise this approach, in combination with relevant histopathological techniques, to test the structural and functional integrity of the dopaminergic system within key fronto-striatal circuits in patients who had exhibited psychomotor phenomena. The same approach can also be used to study the integrity of other relevant biochemical systems, such as the serotoninergic and noradrenergic systems, in patients with other mood disorders.

Brain Mapping↗
PubMed1997

Reproducibility of the Wisconsin cataract grading system in the Blue Mountains Eye Study.

PROBLEM: To measure the inter- and intra-grader reliability of the Wisconsin cataract grading system for grading of nuclear, cortical, and posterior subcapsular cataract (PSC) in the Blue Mountains Eye Study. METHODS: Random samples of lens photographs from study subjects were regraded by each grader according to the Wisconsin cataract grading system. The results were compared using quadratic weighted kappa statistics to derive measures of inter- and intra-grader reliability for the grading of nuclear (5 grades), PSC (3 grades), and cortical cataract (3 grades). RESULTS: Inter-grader reliability (quadratic weighted kappa) for grading of nuclear cataract varied between 0.82 and 0.79; kappa was 0.78 for cortical cataract and 0.57 for PSC. Intra-grader reliability was slightly higher than inter-grader reliability for all three cataract types. CONCLUSION: In the Blue Mountains Eye Study, the Wisconsin cataract grading system provided good reproducibility, comparable to that reported from the Beaver Dam Eye Study, endorsing its usefulness in cataract epidemiology.

Australia↗
PubMed1997

The influence of age and intraocular pressure on the optic cup in a normal population.

PURPOSE: To determine the effects of age and intraocular pressure (IOP) on optic cup and neural rim size, and cup-disc ratio in a well defined population free from apparent glaucoma and other optic nerve disease. METHODS: Data were collected on 3654 people, 49 years or older, living in the Blue Mountains, west of Sydney. Examination included subjective refraction and Zeiss colour stereo (Carl Zeiss, Oberkochen, Germany) optic disc photographs. Magnification effects of the eye and camera were corrected. After excluding subjects with optic nerve diseases, data from 6579 normal phakic eyes of 3358 subject (91.9% of those examined) were used. RESULTS: Adjusted for optic disc size and IOP, cup diameter increased 0.01 mm, cup-disc ratio increased 0.01, and neural rim width decreased 0.01 mm for every decade of age increase. Adjusted for age and optic disc size, cup diameter increased 0.01 mm, cup-disc ratio increased 0.04, and neural rim width decreased 0.07 mm for every 10 mmHg increase in IOP. The IOP-related increase in cup-disc ratio amounted to 9.5% of the mean per 10 mmHg, while the age related increase was 1.9% of the mean. CONCLUSIONS: These data support the hypothesis that there is an age-related loss of tissue from the neuroretinal rim. However the mean change between the ages of 50 and 90 years is very small. The association between increasing IOP and smaller neural rim width could suggest a causal relationship. However, it is also plausible that IOP and optic cup size are both determined by other unmeasured factors.

Aged↗
PubMed1997

An attempt to give nursing home residents a voice in the quality improvement process: the challenge of frailty.

Advanced frailty and confusion of many nursing home residents present a particular conundrum to researchers committed to resident participation. While the research is set in Australia, the challenge of frailty is common to researchers working with compromised older persons. This study was conducted in an Australian 32 bed nursing home. As researchers we took on the roles of facilitators and negotiators within a quality improvement process using the approach of fourth generation evaluation. The overall aim of the project was to provide all stakeholders, including residents and their significant others, with a voice in the negotiations and decisions that impact on their lives. The focus of this paper is our attempt to gain the perspective of residents and significant others.

Aged↗
PubMed1996

Depressive psychomotor disturbance, cortisol, and dexamethasone.

We examine the dexamethasone suppression test as a biological correlate of melancholia as defined by the CORE system, a scale for rating objective signs of psychomotor disturbance. Postdexamethasone cortisol concentrations and rates of nonsuppression were higher in CORE, Newcastle, and DSM-III-R defined melancholic groups. These differences, however, were no longer significant after partialling out the combined effects of age, dexamethasone, and basal cortisol concentrations. There was a significant correlation between the CORE (but not the Newcastle) scale and 8:00 AM postdexamethasone cortisol levels, which persisted after partialling out those same three covariates. Dexamethasone concentrations themselves were lower in CORE- and Newcastle-defined melancholics, though these were no longer significant after covarying for cortisol concentrations. Dexamethasone levels were also significantly inversely correlated with CORE and Newcastle scales. A significant correlation between CORE (but not Newcastle) scores and dexamethasone levels at 4:00 PM persisted after partialling out the effects of age and cortisol. These findings indicate an intriguing relationship between the CORE system as a dimensional construct for rating psychomotor disturbance, and both postdexamethasone cortisol and dexamethasone concentrations.

Age Factors↗
PubMed1996

Tetanus immunity in an older Australian population.

OBJECTIVE: To evaluate the effectiveness in older Australians of the current tetanus vaccination program. DESIGN: A cross-sectional survey of tetanus immunity (enzyme immunoassay of serum samples) in an older population in New South Wales. Self-reported history of tetanus vaccination was compared with serologically measured immunity. PARTICIPANTS: 430 randomly selected adults, 49 years of age and older, from the Blue Mountains Eye Study population. RESULTS: Fifty-two per cent (95% confidence interval [CI], 47%-57%) of adults 49 years of age and older had protective levels of tetanus antitoxin ( > 0.15 IU/mL). There was a significant decline in the prevalence of immunity with increasing age (chi 2 for linear trend, P = 0.036), and women were less likely to be immune regardless of their age (Mantel-Haenszel weighted odds ratio, 0.65; CI, 0.43-0.92). Thirty-five per cent (95% CI, 31%-40%) of all participants reported that they had been vaccinated in the preceding 10 years. Although self-reported tetanus vaccination history was associated with tetanus immunity, it was neither sensitive nor specific as a test for immunity. CONCLUSIONS: About half the adults 49 years of age and older in the Blue Mountains area of New South Wales do not have protective levels of tetanus antitoxin because of inadequate vaccination coverage in this age group. Vaccination history is not a reliable indicator of tetanus immunity and a system is needed for accurate recording of adult vaccination.

Adult↗