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Biomedical subjects

A J Bron

Publications and source records attributed to A J Bron.

At least 73 records · Page 4Linked to original sources
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

A method for measuring neuroretinal rim area.

A practical method for measuring the neuroretinal rim area (NRA) of the optic nervehead is described. Sequential stereo photographs are taken on 35 mm colour transparencies using a Zeiss fundus camera with Allen stereoseparator. While examining a stereo pair with a pocket viewer the disc and cup margins are traced against the stereo image with a Rotring pen (0.1 mm tip) on a clear transparency overlying one of the photographs. This tracing is digitised and analysed by an 'edge detection' algorithm which measures the area between the traced lines, i.e. NRA. The intraobserver intraphotograph coefficient of variation (standard deviation/mean) was calculated for measurements of disc area, cup area and NRA made on 10 stereo photographs of discs with various topographies. Coefficients for NRA ranged from 3.2% to 3.9% for discs with easily discernible cup margins and from 1.6% to 7.2% for discs with less obvious cups.

Glaucoma↗
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↗
PubMed1990

The lens after renal transplantation.

A single masked observer examined 55 non-diabetic patients chosen randomly from a population of patients who had undergone renal transplant. The mean age was 41 years and mean time from transplant was 4.4 years (1-10 years). Fourteen patients were found to have a posterior subcapsular cataract (PSC). The axial thickness of the right lens of the renal transplant population, even in the presence of a PSC, was significantly larger than in a control population of 99 patients with clear lenses. The PSC of renal transplantation is readily distinguished from age related PSC because the opacity lies in the superficial cortex at a depth proportional to time from transplant and the lens maintains a normal anterior clear zone. It is proposed that this type of cataract be called 'recovering' PSC. It is concluded that the cataractogenic insult occurs mainly during the peritransplant period. Maintenance doses of immunosuppressives or steroids are therefore probably not cataractogenic.

Adult↗
PubMed1990

Macular corneal dystrophy: reduction in both corneal thickness and collagen interfibrillar spacing.

The interfibrillar spacing of collagen fibrils was measured at twenty different positions across a macular dystrophy cornea using synchrotron X-ray diffraction. Unlike previous work of this type the cornea had not been frozen for storage. The spacings were all significantly lower than the spacings which existed at similar positions across a normal adult human cornea. This close-packing of collagen fibrils seems to be responsible for the reduced thickness of the central cornea in macular dystrophy. Neither the patient's serum or corneal tissue contained appreciable amounts of sulfated keratan sulfate, this classifies the disease as Type I macular corneal dystrophy.

Adult↗
PubMed1989

Macular corneal dystrophy: the macromolecular structure of the stroma observed using electron microscopy and synchrotron X-ray diffraction.

The distribution of sulphated proteoglycans within the stromas of three patients (A,B,C) suffering from macular corneal dystrophy was studied using the specific dye Cuprolinic Blue in a 'critical electrolyte concentration' method. The corneas were examined using transmission electron microscopy and A and C were further studied by low-angle synchroton X-ray diffraction. Sera from all three patients were analyzed for the presence of keratan sulphate using a monoclonal antibody in an enzyme-linked immunosorbent assay. The serum from Patient A contained keratan sulphate, but the chains were thought to be shorter or less sulphate in their sera. Electron microscopy showed many electron-transparent lacunae randomly distributed throughout the specimens. The average collagen fibril diameter was normal but there were differences in packing between the specimens. Specimen A was closely-packed with most collagen fibrils in contact with their neighbours. Specimens B and C showed fewer regions of close packing; in most of the tissue the interfibrillar spacing appeared normal. Staining with Cuprolinic Blue revealed an unusual distribution of proteoglycans in some parts of the interfibrillar matrix, particularly in A, with 'small' proteoglycans running exclusively parallel to the collagen fibrils. Furthermore in A, and to a lesser extent in B and C, some lacunae were filled with clusters of abnormal sulphated proteoglycan filaments (of various sizes) which were chondroitinase ABC susceptible. Clearly defined regions, both within the lacunae and elsewhere, failed to stain with Cuprolinic Blue; this suggests an absence of sulphated proteoglycans within these areas. Equatorial X-ray diffraction of the wet tissues (A and C) gave values for the mean interfibrillar centre-to-centre separation of 43 +/- 2 nm in Specimen A and 52 +/- 3 nm in Specimen C. The differences observed in the serum keratan sulphate levels, the packing of the collagen fibrils and the distribution of chondroitin/dermatan sulphate proteoglycans confirm the heterogeneity that exists within the macular corneal dystrophies.

Chondroitin Sulfates↗
PubMed1989

The ocular surface in keratoconjunctivitis sicca.

The ocular surface is altered in kerato-conjunctivitis sicca, a disorder of aqueous tear production. Many of the factors leading to these surface changes are now more clearly understood and are discussed in this paper.

Conjunctiva↗