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Biomedical subjects

A J Bron

Publications and source records attributed to A J Bron.

At least 19 recordsLinked to original sources
PubMed1992

Changes in light scatter and width measurements from the human lens cortex with age.

Light scatter and width measurements of the anterior cortical layers of the human lens were made in 50 eyes of 50 subjects using computerised linear scanning densitometry of Scheimpflug images. It was demonstrated that the amount of light scatter increased with age in all of the three major zones and that zone C3 showed the most marked increase. Most lens growth occurs in zone C2 with C3 showing little increase in width once it has become established. Zone C1 showed a tendency to decrease in width with age. In addition it was shown that the C3 zone, which is not present at birth and during early childhood, appears as a distinct layer during the second decade of life. Its scattering properties continue to increase throughout life, exceeding all other zones after approximately 30 years of age, in the absence of cataract. Possible explanations for the lens zone pattern are discussed.

Adolescent↗
PubMed1992

Plasminogen activator in human tears.

Measurements were made of the nature and levels of plasminogen activator in human tears using, as a model of inflammation, patients undergoing cataract surgery. Tissue plasminogen activator (t-PA) but not urokinase plasminogen activator (u-PA) was found in tears. A wide variation in the range of t-PA in pre-operative tears was found. In those patients not receiving per-operative subconjunctival betamethasone a significant rise in t-PA was found in tears on the first post-operative day over pre-operative levels. A significant fall was noted in those receiving per-operative subconjunctival betamethasone.

Betamethasone↗
PubMed1992

The relationship between central nuclear scatter and perinuclear retrodots in the human crystalline lens.

Retrodots are common perinuclear features of age-related cataract. Clinical observation suggested that retrodots were associated with increased nuclear scatter. To test this hypothesis, retrospective data were analysed from 78 non-diabetic subjects (118 eyes), of at least 50 years of age, who had neither subscapsular nor axial spoke opacities. Retrodots were graded using the Oxford Clinical Cataract Classification and Grading system and central nuclear scatter was assessed by image analysis of Scheimpflug photographic negatives. Regression analysis in groups was performed according to the "intra-class correlation model" either considering retrodots as a graded feature (grades 0-5) or as a dichotomous variable (present or absent). After adjusting for age (treated as a co-variate), a highly significant association (P < 10(-6) was found between retrodots and increased nuclear scatter in each analysis. It is suggested that the co-existence of these two cataract types may reflect a common cataractogenic mechanism, possibly oxidative stress.

Aged↗
PubMed1992

Biometry and auto-fluorescence of the anterior ocular segment in diabetics with and without autonomic neuropathy: a case control study.

The biometry and auto-fluorescence of the anterior ocular segment were examined in a case control study of two populations of diabetics. Cases, with diabetic autonomic neuropathy, and controls without neuropathy (forty in each group) were selected from a community based diabetic population and matched individually for age, sex, and type of diabetes. Scheimpflug and auto-fluorescence anterior segment photography were performed and analysed by digital image analysis in a masked fashion. There were differences between the groups in axial lens thickness, front radius of curvature of the lens, anterior chamber depth and lenticular auto-fluorescence. These findings are discussed in the context of the known association between autonomic neuropathy and narrow angle glaucoma, and possible common mechanisms of tissue damage in diabetes.

Aged↗
PubMed1992

Ocular surface residence times of artificial tear solutions.

Solutions of hydroxypropylmethylcellulose (HPMC) and polyvinyl alcohol (PVA) are widely used as artificial tears. However, their usefulness is limited by the short duration of their effect. Dilute sodium hyaluronate (SH) solutions exhibit non-Newtonian rheology with high viscosities at low shear rates, which would be expected to enhance their ocular surface residence time. Using quantitative gamma scintigraphy, estimates of the ocular surface residence times of 0.3% HPMC, 1.4% PVA, and 0.2% SH were made in six patients with keratoconjunctivitis sicca. The sodium hyaluronate solution had a mean half-life on the ocular surface of 321 s, significantly longer than hydroxypropylmethylcellulose (44 s; p = 0.012) and polyvinyl alcohol (39 s; p = 0.013).

Biological Availability↗
PubMed1992

Age-related morphological changes in lid margin and meibomian gland anatomy.

Meibomian gland dysfunction (MGD) is responsible for recurrent irritative symptoms. Attempts to characterize MGD have largely concentrated on microbial and lipid abnormalities in meibomian gland secretions. Few reports describe histological abnormalities in this disease, and fewer still morphological changes. This article follows a previous study that established a classification for MGD. This was based on morphological changes in the meibomian gland and lid margin. Using this classification, we studied the age-related changes in 80 subjects, between 5 and 87 years of age without ocular disease. The lid margin became thicker after childhood. Lid margin vascularity and cutaneous hyperkeratinization increased with age in both lids, whereas, telangiectasia increased with age in the lower lid and squamous blepharitis and posterior lid margin rounding were more common after 50 years of age in the upper lid. Multiple rows of meibomian gland orifices occurred more frequently in the upper than lower lid, and orifice narrowing and pouting increased with age. No age-related changes in the shape or form of the mucocutaneous function, gland ducts, or acini were found. Meibomian gland secretions were less easily expressed in the elderly. We have attempted to define a normal range of lid morphology in healthy children and adults that we believe to be important for the subsequent definition of lid disease, and in particular, posterior blepharitis.

Adolescent↗
PubMed1992

Autofluorescence of the crystalline lens in early and late onset diabetes.

Blue/green autofluorescence (excitation around 420 to 430 nm, emission around 520 nm) of the crystalline lens has been studied by an in vivo photographic method in two populations of diabetics and controls. The populations consisted of a geographically based survivor group of 161 mixed early and late onset diabetics (and 133 non-diabetic controls) and a second group of 104 early onset insulin dependent diabetics (and 138 non-diabetic controls), the latter all with non-cataractous lenses. Powerful associations (p less than 10(-6) were found between the presence of diabetes and increased lenticular autofluorescence in both populations. Among the mixed diabetics diabetic type was a significant factor after accounting for the effects of age and diabetic duration. In the early onset group (clear lenses) a powerful association existed between autofluorescence and diabetic duration (p = 0.000011) after allowing for the effect of age, while in a subgroup of late onset diabetics with clear lenses this effect was modest (p = 0.015). In the early onset diabetic group diabetic retinopathy (p = 0.0064) was associated with increased lenticular autofluorescence after allowing for the effects of age and diabetic duration. In addition a powerful interaction between diabetic duration and the presence of diabetic retinopathy (p less than 10(-6) was found in this subgroup. Among the geographically based population of diabetics, increased nuclear brunescence was powerfully associated (p less than 10(-6) with increased autofluorescence after allowing for the effects of age, diabetic duration, and type of diabetes. This association was not found in the non-diabetic population. Non-enzymatic glycosylation of lens proteins should be considered as a possible mechanism of production of the fluorogen with emission around 520 nm.

Adolescent↗
PubMed1992

Biometry of the crystalline lens in late onset diabetes: the importance of diabetic type.

Lenticular and anterior chamber biometry were studied in non-cataractous eyes by means of Scheimpflug photography and digital image analysis. The study population consisted of 91 late onset diabetic subjects and 115 non-diabetic controls. Anteroposterior axial lens thickness, cortical thickness, nuclear thickness, anterior clear zone thickness, anterior chamber depth, and anterior and posterior lenticular curvatures were assessed. Age played an important role in determining lens biometry in all subjects, and small but significant differences were found between late onset diabetics and non-diabetics. In the late onset diabetic subgroup, apart from age, diabetic retinopathy was the only significant parameter found which determined lens biometry. These biometric findings in late onset diabetes are in marked contrast to the large overall effect of diabetes and the powerful effect of diabetic duration which we previously reported in early onset diabetes. Further analysis of the data from our previous study has been provided, which clearly demonstrates differences between the impact of early and late onset diabetes on the biometry of the anterior ocular segment.

Adult↗
PubMed1991

Growth spurt in a lens with a posterior subcapsular cataract.

Over a period of 5 years, the lenses of a patient with a unilateral posterior subcapsular cataract were documented using Scheimpflug slit-image photography. For the first time ever, a growth spurt was observed of the cataractous lens. It is postulated that this could be a reflection of either a mitotic spurt of the lens epithelium or a failure of compaction of the deeper lens fibres.

Adult↗
PubMed1991

Ophthalmology in the Oxford region: analysis of time trends from linked statistics.

OBJECTIVES: to report on trends in ophthalmology workload using linked statistical data; DESIGN: analysis of linked abstracts of hospital inpatient and day case records for ophthalmology; SETTING: six districts in Southern England covered by the Oxford record linkage study; SUBJECTS: records for hospital admissions to ophthalmology from 1975 to 1985; MEASUREMENTS AND MAIN RESULTS: Over the period of study, the number of episodes of inpatient and day case care increased by 16.3%. Notable increases in age-specific admission rates were seen among the elderly. An increase in the number of individuals treated contributed about 67% and an increase in multiple admissions per individual contributed about 33% to the increase in admission rates. Both average length of stay per episode and total time in hospital per individual decreased consistently during the 11 years; and there was no increase in emergency readmissions over time. No significant changes over time were found in admission rates for retinal detachments and defects or for glaucoma. There was a statistically significant increase averaging 4.8% per annum in admission rates for cataract, and a significant decrease averaging 5.2% per annum in admission rates for strabismus and other disorders of binocular eye movement between 1975 and 1985. CONCLUSIONS: Age-specific admission rates in ophthalmology are much higher in the very young and old than in other age groups. Patterns of work in the specialty are therefore particularly affected by variation in the age distribution of the population. The increase in cataract surgery reflected both the increase in numbers of old people in the population and an increase in age-specific operation rates for cataract. Attempts to alter attitudes and behaviour of the elderly regarding eye diseases, disability, and facilities for treatment may have had a positive impact on the use of services. The decrease in admissions for children probably reflects the impact made by child health surveillance programmes. As the child screening programme has expanded, the admission rates for strabismus have decreased.

Adolescent↗
PubMed1991

Meibomian gland disease. Classification and grading of lid changes.

In recent years attention has been paid to meibomian gland dysfunction (MGD) as a distinct clinical entity responsible for chronic symptoms and signs and occurring independently or in association with atopy, cicatrising mucosal disorders and rosacea. Attempts to correlate MGD with microbiological and lipid biochemical changes are confounded by the absence of a clear descriptive language for the disorder and its associated changes. Such a language is crucial for the conduct of cross-sectional and natural history studies and therapeutic clinical trials. We present a comprehensive classification and grading scheme of meibomian gland disease, supporting our observations with illustrations.

Adolescent↗
PubMed1991

Ofloxacin compared with chloramphenicol in the management of external ocular infection.

The safety and efficacy of 0.3% ofloxacin in treating bacterial ocular infections was compared with that of 0.5% chloramphenicol in a parallel-group, randomised clinical trial at five sites. Clinical and microbiological improvement rates were studied in 84 culture-positive patients. Patients with suspected bacterial ocular infections were evaluated for clinical improvement and were included in drug safety and comfort analyses. Clinical improvement did not differ significantly between drug treatments. All patients completing the study (79 assigned ofloxacin, and 74 chloramphenicol) showed clinical improvement. Clinical improvement in the culture-positive groups was 100% (41/41) after ofloxacin treatment, and 95% (41/43) after chloramphenicol treatment. Microbiological improvement rates were similar for the two drugs: 85% (33/39) improved with ofloxacin, and 88% (38/43) improved with chloramphenicol. Both drugs were well tolerated. Adverse reactions possibly due to the study medication occurred in 1% (1/89) of those who received ofloxacin, and in 4% (4/93) of those who received chloramphenicol.

Adult↗
PubMed1990

Precorneal residence times of sodium hyaluronate solutions studied by quantitative gamma scintigraphy.

Sodium hyaluronate solutions have been advocated in the management of a variety of dry-eye states. By virtue of their non-Newtonian rheological properties, formulations exhibiting high zero-shear viscosities may be used as an artificial tear with the expectation of prolonged precorneal residence times and improved tolerance. Quantitative gamma scintigraphy was used to evaluate the residence times of 0.2% and 0.3% sodium hyaluronate solutions and a polymer-free solution of buffered saline in 12 patients with keratoconjunctivitis sicca and a group of six normal volunteers. Using several indices of residence time, mean values for the sodium hyaluronate solutions were significantly longer than those for buffered saline. Parallel changes in tear film thickness were also demonstrated using a technique based on laser interferometry.

Adhesiveness↗
PubMed1990

The Oxford modular cataract image analysis system.

A modular system of acquisition and analysis of Scheimpflug, retro-illumination and fluorescence images of the in vivo human crystalline lens is described. Image analysis is directed towards the following goals: Scheimpflug slit-images are analysed for: (1) The optical density of nuclear cataract present; (2) The dimensions of the lens and the lenticular zones; (3) The curvatures of the lens and lenticular zones. Retro-illumination images are analysed for: (1) The percentage area which is occupied by cataract; (2) A combined measure (weighted integral) describing both the amount of cataract present and its optical density. Lenticular auto-fluorescence images are analysed for the mean density (fluorescence) of the lens as a whole. A pilot study of the repeatability of the methods is presented.

Cataract↗
PubMed1990

Biometry of the crystalline lens in early-onset diabetes.

Lenticular biometry on non-cataractous lenses has been studied by means of Scheimpflug photography and digital image analysis in 153 patients with early-onset insulin-dependent diabetes and 153 non-diabetic controls. Anteroposterior axial lens thickness, cortical thickness, nuclear thickness, anterior and posterior lenticular curvatures, and anterior chamber depth were assessed. Highly significant differences between the lenses of the diabetic subjects and non-diabetic controls were found. After the effect of age had been accounted for within the diabetic subgroup, diabetic duration was found to be a highly significant determinant of lens dimensions, such that age-related dimensional changes for various biometric parameters were accelerated by between 52% and 121% after the onset of diabetes. Because the diabetic duration of the early-onset diabetic subjects studied in this work was accurately known, this report is the first in which a precise assessment of the effect of 'true' diabetic duration on lens biometry has been possible.

Adolescent↗
PubMed1979

Epithelial deposition of gold in the cornea in patients receiving systemic therapy.

Epithelial gold deposits were demonstrated biomicroscopically in 13 of 15 patients receiving gold therapy for rheumatoid arthritis. Only one of six further patients who had received gold therapy in the past showed such deposits. Deposits appeared with a cumulative dose of sodium thiomalate exceeding 100 mg. The earliest appearance was after seven months of therapy and deposits were visible in one subject as long as nine months after therapy had stopped. The density of deposit does not appear to increase over the whole of the dose range, possibly as a result of the effect of epithelial turnover. No symptoms attributable to the deposit were encountered in any patient.

Adolescent↗
PubMed1979

The intraocular penetration of cefuroxime after parenteral administration.

Cefuroxime (Zinacef) is a new second generation cephalosporin which is resistant to beta-lactamases produced by both Gram-negative and Gram-positive organisms, with an antibacterial spectrum that includes practically all likely ocular pathogens except pseudomonas. It is shown to penetrate into the eye after intravenous (1.5g) or intramuscular (1 g) injection and achieve therapeutic concentrations, with absence of side effects. Cefuroxime is therefore a useful antibiotic for ophthalimic infections and should have a role in combination with gentamicin in intraocular infections, particularly those of unknown aetiology.

Adult↗