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Biomedical subjects

G N Dutton

Publications and source records attributed to G N Dutton.

At least 55 records · Page 3Linked to original sources
PubMed1997

Determination of molecular weight of hyaluronic acid in bovine vitreous humour and Healon by high performance gel permeation chromatography and its depolymerization with ascorbic acid.

A method has been developed for the determination of the molecular weight of hyaluronic acid by high performance gel permeation chromatography. The molecular weight distribution was determined using three polymeric columns. Columns were calibrated using Pullulan Polymer molecular weight standards. The average molecular weight (+/- SD) of the hyaluronic acid in bovine vitreous humour and Healon were 1.20 x 10(6) Da (+/- 0.49 x 10(6) and 3.01 x 10(6) Da (+/- 0.14 x 10(6), respectively. Furthermore, the depolymerization of the hyaluronic acid in the presence of ascorbic acid (the concentration found in human eye) was studied. Samples incubated in the presence of atmospheric air showed more depolymerization than those where atmospheric air had been flushed-out with nitrogen.

Animals↗
PubMed1996

Classification system and case definitions of Toxoplasma gondii infection in immunocompetent pregnant women and their congenitally infected offspring. European Research Network on Congenital Toxoplasmosis.

Classification systems and case definitions provide the foundations upon which clinical and epidemiological studies are based. The European Research Network on Congenital Toxoplasmosis acknowledged the lack of such a system or definitions within its field of interest and established a working group to address the issue. Congenital Toxoplasma gondii infection was defined as occurring in four separate patient groups: pregnant women, fetuses, infants, and individuals > 1 year of age. The likelihood of Toxoplasma gondii infection was separated into five mutually exclusive categories: definite, probable, possible, unlikely, and not infected. Inclusion within a specific category is dependent upon the case definition, which is in turn derived from criteria based on serological, parasitological, and clinical information. Notes are included within the classification not only to clarify the definitions, but also to improve the reliability and quality of diagnosis. The goal is to construct a system that encompasses all aspects of congenital toxoplasmosis, which is applicable to different countries and health services, suitable for large epidemiological studies, aids the diagnosis and management of individual cases, and lends itself to computerisation.

Female↗
PubMed1996

Treatment of retrobulbar haemorrhage in accident and emergency departments.

Retrobulbar haemorrhage is a rare complication of orbital injury or surgery. After injury the first clinicians to see these patients are often the staff of accident and emergency departments. This survey was instigated after several patients had been referred to our care irreversibly blind. A multiple choice questionnaire was devised and sent to 90 doctors working in accident and emergency departments in Scotland. A total of 57 (63%) were returned of which 55 were complete enough to analyse. The range of respondents was: consultants (n = 6), associate specialists (n = 3), senior registrars (n = 3), registrars (n = 4), senior house officer (n = 35), and clinical assistants (n = 4). Twenty nine of the 35 senior house officers (83%) were unable to diagnose and treat retrobulbar haemorrhage. Most consultants, senior registrars, registrars and associate specialists were significantly better in the diagnosis and treatment of this condition (P = 0.001). We conclude that there is an unacceptably high incidence of blindness as a result of inappropriate diagnosis and treatment of retrobulbar haemorrhage. We have therefore designed a protocol for accident departments which should help reduce the incidence of blindness.

Acetazolamide↗
PubMed1996

Cognitive visual dysfunction in a child with cerebral damage.

Visual impairment as a sequel to cortical damage can be associated with complex disorders in cognitive visual function. Such dysfunction can be difficult to diagnose with certainty, particularly in children, owing to the child's problems of awareness and communication. The authors describe the case of a 13-year-old girl whose cerebral damage is apparently accompanied by complex cognitive visual disorders. Though she has a good binocular visual acuity, she cannot see rapidly moving objects. She has difficulties with orientation, recognising faces and cognitive depth perception. Despite an absence of detailed psychometric testing, a clinical diagnostic approach such as that used in this case, based on a CT scan and careful history-taking and observation, may be helpful in planning educational strategies.

Adolescent↗
PubMed1996

Visual acuity assessment of children with neurological impairment using grating and vanishing optotype acuity cards.

We have compared the testability and acuity thresholds achieved with vanishing optotype acuity cards and traditional grating acuity cards when used to examine children with neurological impairment. These children encompass a wide range of ages and abilities and it may be desirable to use the two types of cards for acuity assessment. Subjects were a diverse group of children (n = 91; 8 months-19 years) whose learning ability ranged from normal to severe disability. There was no significant difference between the individual success rates for the two sets of cards (grating 91% (n = 61) vanishing optotype 89% (n = 59)). Over a wide range of acuities (0 to 2.0 LogMAR) the mean difference between acuity thresholds did not differ significantly from zero (p = 0.24). Ninety-three percent of acuity estimates agreed to within +/- 0.50 LogMAR units. The results indicate that the two acuity tests could be used interchangeably in clinical populations of children with neurological impairment.

Adolescent↗
PubMed1995

A comparison of colour Doppler imaging of orbital vessels and other methods of blood flow assessment.

BACKGROUND: Comparison of the haemodynamic measurements obtained by colour Doppler imaging and other methods of ocular blood flow measurements was desired. METHODS: The blood velocity findings from colour Doppler imaging of patients with central retinal vein occlusion were compared to the results of fluorescein video-angiography, continuous tonography and ophthalmodynamometry. RESULTS: Patients with low or undetectable blood velocities in the central retinal vein had longer retinal dye transit times on fluorescein video-angiography. Tonography showed a positive correlation with the velocities in the ophthalmic artery, but ophthalmodynamometry showed a negative correlation with these velocities. CONCLUSION: The relationships between the blood velocities in orbital vessels and other blood flow measurements emphasise that there is a complex interaction of the blood flow parameters. Care must therefore be taken when interpreting the results of studies.

Aged↗
PubMed1995

Quantitative assessment of the blue-light hazard during indirect ophthalmoscopy and the increase in the "safe" operating period achieved using a yellow lens.

PURPOSE: The indirect ophthalmoscope presents a blue-light hazard with the potential for causing photochemical injury to the retina. In this study, this hazard was assessed with respect to the threshold limit values (TLVs) recently adopted by the American Conference of Governmental Industrial Hygienists. METHOD: Spectral radiometric measurements were made from a standard indirect ophthalmoscope headset used in conjunction with either a clear or a yellow lens. The results were weighted spectrally with the published blue-light hazard function. RESULTS: When the clear lens was used, the TLV was exceeded after approximately 2.5 minutes. The yellow lens filtered out the more hazardous blue wavelengths of light and this increased the "safe" operating period by a factor of approximately 20. CONCLUSION: In clinical practice, with a clear lens, the TLV could be exceeded easily if the patient is subjected to prolonged or repeated examination because the blue-light hazard is additive in a linear manner for periods as long as 3 hours with a potential for a cumulative effect over longer periods. Furthermore, some ophthalmic patients, such as those with aphakia, are less tolerant of blue-light than healthy subjects. In the interests of patient safety, it is recommended that yellow lenses are considered for use for routine indirect ophthalmoscopy.

Equipment Safety↗
PubMed1995

Comparison of visual assessment tests in multiply handicapped children.

The aims of this study were to compare acuity estimates achieved with visual evoked potential (VEP) and acuity card techniques and to examine the success rates of each test in a group of multiply handicapped children. Subjects were 52 children (3-183 months) with multiple handicaps associated with prematurity (n = 17), congenital anomalies (n = 16), hypoxic insult (n = 10) and other disorders (n = 9). Success rates for completing the tests were: VEP 88% and acuity cards 85% (Keeler or Cardiff). The acuity card tests were less likely to be successfully completed in the severely disabled (p < 0.05) and in those children with nystagmus (p < 0.05). When both acuity cards were successful, results agreed to within +/- 1.75 octaves. Acuity card thresholds were significantly correlated with VEP thresholds (p < 0.02), but thresholds achieved with VEPs were better in children with poor vision.

Adolescent↗
PubMed1995

Assessment of an inner city visual screening programme for preschool children.

AIMS: The efficiency of preschool visual screening programmes to detect amblyopia is questionable. In this study such a programme in an inner city was assessed to determine its effectiveness. METHODS: The results of screening and hospital treatment of 712 patients who were considered to require referral were entered into a database for analysis. Default rates were assessed and the efficacy of treatment determined. RESULTS: The only effective screening test for the detection of amblyopia was visual acuity. A large proportion of referred patients had refractive problems only. High default rates, particularly in geographical areas of lower socioeconomic grading, severely handicapped any attempt to reduce the incidence of amblyopia. CONCLUSION: A fresh approach to the detection and care of amblyopia in the inner city community is required, perhaps by performing screening of children in their first year of attendance at school to reduce default rates. Cycloplegic refraction of children who are found to have reduced visual acuity before their referral to hospital is also recommended.

Amblyopia↗
PubMed1994

The simultaneous interocular brightness sense test. A test of optic nerve function.

OBJECTIVE: To describe and establish control data from controls for a simultaneous interocular brightness sense test in which the apparent brightness of two independently viewed light patches was compared. DESIGN: Dichoptic viewing was achieved by dissociation of right and left eyes using a septum and cross-polarization. Brightness matches were obtained by using adjustments to the illumination of the left retina while the illumination of the right retina was kept constant. OBSERVERS: Ninety-one control observers (age range, 20 to 91 years) participated in the study to provide normal brightness-matching data. RESULTS: Effects from ocular dominance, age, and long- and short-term adaptation were negligible, but the test was sensitive to anisocoria. Just noticeable differences in dichoptic brightness matching were proportional to retinal illuminance; this finding was consistent with the Weber-Fechner law. CONCLUSION: The test is quick and simple to complete and appears to offer considerable scope for the assessment of visual function when differences in the functional integrity of the optic nerves of the right and left eyes are suspected.

Adaptation, Ocular↗