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Biomedical subjects

C G Owen

Publications and source records attributed to C G Owen.

14 recordsLinked to original sources
PubMed2006

The epidemiology of medical treatment for glaucoma and ocular hypertension in the United Kingdom: 1994 to 2003.

AIMS: To study trends in the prevalence of being treated for glaucoma and ocular hypertension from 1994 to 2003, and to examine factors determining treatment in 2002. METHODS: Computerised data (the DIN-LINK database) from 131 general practices across the United Kingdom, in which half a million patients aged 40 years or more were registered annually, were used. On average 10 000 patients were treated for glaucoma and ocular hypertension annually. RESULTS: Prevalence of being treated for glaucoma and ocular hypertension increased from 1.7% in 1994 to 2.3% in 2003. Those aged 85 years or more were 13 times (95% CI 12.2 to 13.8) more likely to be treated than those aged 40-64 years. Men were more likely to be treated than women (OR 1.24, 95% CI 1.19 to 1.28). Subjects "hard pressed" were less likely to be treated than "wealthy achievers" (OR 0.92, 95% CI 0.86 to 0.99). While use of topical beta blocker only medications has declined since 1995, use of topical prostaglandins and combination therapies has increased. In 2003, use of prostaglandins overtook beta blocker only medications. CONCLUSION: Prevalence of being treated for glaucoma has increased over time, and rises with age. Differences in treatment by sex and social status could be explained by use of or access to health care or by underlying prevalence of disease. Trends in treated glaucoma emphasise the shift from use of topical beta blockers to newer therapies.

Adrenergic beta-Antagonists↗
PubMed2005

British South Asians aged 13-16 years have higher fasting glucose and insulin levels than Europeans.

AIM: To examine whether plasma glucose, insulin resistance and markers of adiposity differed between British adolescents of South Asian and European origin. METHODS: School-based cross-sectional study (1998-2000), in which detailed measurements of adiposity, fasting plasma glucose and serum insulin were made in 90 South Asian and 1248 European pupils (overall 69% response rate). RESULTS: Compared with Europeans, South Asian subjects had higher mean fasting insulin levels (percentage mean difference 17.2%, 95% confidence interval 7.2-26.1%, P = 0.001), a higher mean fasting glucose (mean difference 0.19 mmol/l, 95% confidence interval 0.08-0.29 mmol/l, P = 0.0005) and a higher prevalence of impaired fasting glucose (> or = 6.1 mmol/l) (5.6% vs. 1.5%, odds ratio 3.9, 95% confidence interval 1.4-10.9, P = 0.004). Although South Asian children tended to have slightly higher indices of adiposity than Europeans (other than body mass index), the differences in glucose and insulin levels persisted after adjustment for adiposity and for pubertal status. CONCLUSIONS: The predisposition to Type 2 diabetes observed in South Asian adults is apparent before adult life. Establishing the contributions of the childhood and fetal environments and of genetic factors to the development of these ethnic differences is an important priority. Prevention of Type 2 diabetes in British South Asians needs to begin before adult life.

Adipose Tissue↗
PubMed2003

How big is the burden of visual loss caused by age related macular degeneration in the United Kingdom?

AIMS: To predict the burden of blindness, partial sight, and visual impairment (binocular visual acuity 6/18 or less) due to late stage age related macular degeneration (AMD) in the ageing population of the United Kingdom. METHODS: A systematic review, followed by a request for data, was used to establish a pooled prevalence of AMD and corresponding visual loss. Prevalence figures were applied to the UK population. Using UK population trends, the future burden of AMD over the coming decade was established. RESULTS: Pooled data from six studies showed that the prevalence of visual loss caused by AMD increased exponentially from the age of 70-85 years of age, with 3.5% (95% CI 3.0 to 4.1) having visual impairment beyond the age of 75 years. The authors estimate that there are currently 214 000 (95% CI 151 000 to 310 000) with visual impairment caused by AMD (suitable for registration). This number is expected to increase to 239 000 (95% CI 168 000 to 346 000) by the year 2011. Currently there are 172 000 (95% CI 106 000 to 279 000) and 245 000 (95% CI 163 000 to 364 000) with geographical and neovascular AMD, respectively. CONCLUSIONS: Estimates of visual impairment agree with official statistics for the number registered partially sighted or blind, caused by AMD, and are well below other figures often cited. Although these estimates are associated with wide confidence intervals (CI) and a number of caveats, they represent the best available data, which can be used to guide health and social care provision for older people in the UK setting. Implications for low vision services are outlined.

Age Distribution↗
PubMed2001

Nonlinear behavior of certain optic nerve head parameters and their determinants in normal subjects.

OBJECTIVE: To investigate the relationship between the absolute area of certain optic disc parameters and a number of ocular dimensional characteristics and demographic factors in young, healthy subjects. DESIGN: Cross-sectional study. PARTICIPANTS: One hundred twenty-one subjects, aged 16.5 to 35.4 years participated, encompassing a wide range of refractive error from +4 diopters (D) to -25.75 D. One eye from each subject was randomly selected for examination. MAIN OUTCOME MEASURES: Absolute size of the optic disc parameters: optic disc area (DA), neuroretinal rim area (NRA), optic cup area (CA), and peripapillary atrophy area (PA). METHODS: Absolute sizes of optic disc parameters were determined from digitized photographic color transparencies, taking into consideration the magnification of the fundus camera and human eye. Relationships between the absolute size of the optic disc features and axial length, crystalline lens thickness, anterior chamber depth, ocular refraction, front surface keratometry, age, and gender were examined. RESULTS: Axial length, lens thickness, front surface keratometry, and age demonstrated positive associations with all optic disc parameters, and anterior chamber depth and ocular refraction demonstrated negative associations in all cases. Multiple regression analysis revealed that the associations observed univariately for age, anterior chamber depth, lens thickness, front surface keratometry, and ocular refraction were confounded by axial length for all disc parameters. After taking logs, DA and NRA exhibit an exponential relationship with axial length, whereas PA and CA exhibit a linear relationship with axial length. DA and NRA increase by approximately 3% per millimeter increase in axial length at 20 mm and up to 40% for DA and 50% for NRA at an axial length of 35 mm. PA and CA are estimated to increase by 26% (10%-44%) and 10% (5%-16%), respectively, per millimeter increase in axial length. Females have approximately 5% smaller DA and 7% smaller NRA than males, but these effects are not statistically significant (P > 0.2). From the multiple regression analysis, females have 31% larger optic cup areas (1%-57%, P = 0.03) and 24% smaller PA (42% smaller to 5% larger P = 0.06) than males, but these effects are of borderline statistical significance at 5%. CONCLUSIONS: Of the ocular biometric factors considered, axial length seems to be the most important predictor of the absolute area of the optic disc parameters. No association exists between any disc parameter and age in this sample of subjects less than 40 years of age. Females exhibited smaller values for DA, NRA, and PA than did males, differences that were not statistically significant, and larger CA (P = 0.03).

Adolescent↗
PubMed1997

Use of contact lenses by firefighters: Part 2. Clinical evaluation.

Contact lenses can be worn in a variety of environmental conditions and do not increase the wearers risk of injury. In many situations they offer significant corneal protection. Currently firefighters are prohibited from using contact lenses. To evaluate whether contact lenses are a safe form of visual correction 50 firefighters were fitted, and examined after 1, 4 and 10 months of contact lens wear. Twenty-nine were fitted with soft contact lenses, and 21 with rigid gas permeable contact lenses. Statistically significant increase in lid sulcus hyperaemia was found in both the SCL and RGPCL groups (P < 0.01, P = 0.02, respectively), as well as an increase in hyperaemia of the vertical quadrant of the bulbar conjunctivae (P = 0.01, P = 0.02, respectively). In addition the RGPCL group showed a statistically significant increase in hyperaemia of the lateral portion of the bulbar conjunctivae (P < 0.01), consistent with exposure epitheliopathy. The SCL group showed statistically significant increase in corneal staining in the vertical quadrant for all visits (P = 0.02, P = 0.01, P = 0.02 for all visits, respectively), indicative of lens dehydration. These findings although clinically significant are not unique to firefighting, and are found within a "normal" population of contact lens wearers. In conjunction with questionnaire data (Owen et all, 1996) we conclude that soft contact lenses can be worn safely by firefighters without additional risk.

Analysis of Variance↗
PubMed1997

Use of contact lenses by firefighters. Part 1: Questionnaire data.

The use of contact lenses by firefighters is currently prohibited. However, many firefighters may benefit from this form of visual correction, without predisposing themselves to additional risk. Visual benefits gained by contact lens wear may increase a firefighter's safety. To determine if it is safe to allow firefighters to use contact lenses 29 were fitted with soft contact lenses and 21 with rigid gas permeable contact lenses. Questionnaires were completed prior to fitting, after 1, 4 and 10 months of contact lens wear. Both soft contact lens (SCL) wearers, and rigid gas permeable contact lens (RGPCL) wearers showed a statistically significantly reduction in the frequency with which they experience irritable foreign bodies and irritant fumes in the eyes, compared to not wearing contact lenses. Firefighters felt that their performance on the fireground had been improved by the use of contact lenses. SCL wearers also benefited from a reduction in the frequency with which they experienced watery eyes and ocular discomfort. There were significantly fewer problems encountered with SCL wearers than RGPCL wearers. The frequency with which firefighters experienced lenses falling out, lens displacement, watery eyes, ocular discomfort, and operational difficulties was significantly less for the SCL group than the RGPCL group. SCL appear to offer considerable benefits for firefighters with refractive error, but their use cannot be sanctioned without assessment of their effect on the ocular adnexa.

Adult↗
PubMed1996

Optimal photographic imaging of the bulbar conjunctival vasculature.

A method for imaging the conjunctiva to yield greater contrast between the vasculature and the scleral background, by optimisation of the imaging system, is described. A simple modification to the image capture system, based on first principles calculations, is shown to give images with much improved information content. This will enhance the assessment of hyperaemic changes induced by foreign materials, indicating the degree of biocompatibility, e.g. with contact lenses and ophthalmic medications. Observation of vascular abnormalities associated with pathological conditions may assist in their diagnosis and monitor progressive changes.

Adult↗
PubMed1996

Colour vision requirements of firefighters.

To perform their job safely firefighters must be able to identify colours on industrial gas cylinders, portable fire extinguishers, road traffic signals and several pieces of firefighting equipment. Although good colour vision is necessary we believe that the existing colour vision standard, which bars entry to the fire service to applicants who fail more than two plates of the Ishihara test, is unnecessarily stringent. We have identified and quantified the colour coded information encountered by firefighters. Colours were plotted on the CIE chromaticity diagram (1931) and isochromatic zones, which document the colour confusions of colour deficient observers, superimposed. This novel technique established possible colour confusions in different types of colour deficiency. Analysis of the results showed that red/green dichromats (protanopes and deuteranopes), severe deuteranomalous trichromats who fail the Farnsworth D15 test, and protanomalous trichromats are unsuitable for firefighting work. However, people with slight deuteranomalous trichromatism who pass the D15 test, are not disadvantaged and can be employed safely as firefighters. A new colour vision standard and a new testing procedure is recommended.

Color↗
PubMed1996

Prevalence of spectacle and contact lens wear in the UK fire service.

Despite the fact that firefighting has been shown to be a visually demanding occupation, the present visual standards for firefighters prohibit the use of spectacles or contact lenses operationally. To determine the proportion of the UK fire service currently using spectacles and contact lenses, and how many may benefit from optical correction, a questionnaire was distributed. This contained 30 questions and was sent to 1550 firefighters. The data from 1064 returned questionnaires have been analysed. The results show that approximately 20% of those serving in the fire service have used an optical correction at some time in their lives. When not working, approximately 6% of firefighters wear spectacles for distance vision and 15% wear them for reading. Only 0.4% of firefighters use contact lenses. Half of this contact lens wearing group use their lenses while on operational duty. In total, approximately 2% of firefighters use an optical correction for operational duties. The results indicate that a high visual standard at the time of entry into an occupation cannot guarantee good vision throughout an individual's career. In addition, an estimated 11,000 firefighters in the UK, who have spectacles or contact lenses, do not use them for operational duties. The present visual standards prevent this group of firefighters from obtaining their optimal visual performance at work.

Adolescent↗
PubMed1996

A new computer assisted objective method for quantifying vascular changes of the bulbar conjunctivae.

A novel computer software method was used to quantify the conjunctival plexus on the scleral background for measurement of the vascular surface area from photographs. A previously described method was used (Palmer, J. R., Owen, C. G., Ford, A. M., Jacobson, R. E. and Woodward, E. G. (1996). Optimal photographic imaging of the bulbar conjunctival vasculature. Ophthal. Physiol. Opt. 16, 144-149) to optimise photographic imaging of the bulbar conjuctival vasculature by increasing the information content in the image. Repeatability of this technique was evaluated. Twenty subjects (20 eyes) free from ophthalmological and systemic abnormality were examined on two separate occasions. The maximum 95% confidence limits for repeatability are +8.58/-3.95%. For 10 consecutive estimates of vascularity the maximum 95% confidence interval lie between +/- 6.54%. To evaluate the technique the lateral-bulbar conjunctivaein 10 soft (SCL) and 10 rigid gas permeable contact lens (RGPCL) wearers during the first 10 months of contact lens wear, were assessed and compared with subjective grading of hyperaemia. The new method showed sufficient sensitivity in detecting increased hyperaemia in the RGPCL wearing group and demonstrated statistically significant change. Subjective graded assessment of vascularity (using established classifications) detected increased hyperaemia, however, this was not statistically significant. Conjunctival vasculature is a dynamic structure and a source of valuable quantitative information where the ocular environment is varied, or where the ocular surface is affected by disease. Hence it is worthy of further investigation. A simple inexpensive method of computer assisted determination of vascularity is described.

Adult↗
PubMed1995

Aetiology and prevalence of eye injuries within the United Kingdom fire service.

A survey was conducted on a sample of 1552 firefighting personnel to determine the incidence of eye injuries within the United Kingdom fire service. In total, 3.5% (n = 22/637) of firefighters per year will sustain an eye injury requiring 'medical attention'. This represents one ocular injury per 50,000 working hours. In 80% of cases eye protection was not being worn at the time of injury. Analysis of 75 accident report forms indicates that the vast majority (69/75) of eye injuries were sustained whilst on operational duty. These statistics are comparable to other professions which are considered to have an unacceptably high risk of injury and in which eye protection has therefore been actively enforced. It would follow that similar steps should be taken within the fire service to ensure firefighters wear eye protection on operational duty. This should apply even if there is no immediate recognition of a perceived danger. A firefighter presenting to an optometrist or medical practitioner, with or without an eye injury, should be counselled as to the advantages of eye protection.

Accidents, Occupational↗
PubMed1991

Crevice corrosion products of dental amalgam.

The objective of this study was to determine the in vitro corrosion products that resulted from crevice corrosion of low- and high-copper dental amalgams. Specimens were potentiostatically polarized in a chloride-containing electrolyte while set against a PTFE surface to form a crevice. After 16 h, corrosion products were examined by light microscopy, SEM, EDS, and XRD. Analysis showed the presence of three previously reported products [Sn4(OH)6Cl2, SnO, and Cu2O] and a new product, CuCl, which formed on high-copper, gamma 2-free amalgams. Thermodynamic considerations show that CuCl is stable for the reported in vivo potentials of amalgam restorations and the high acidity and high chloride ion concentration associated with crevice corrosion.

Copper↗