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Biomedical subjects

A R Fielder

Publications and source records attributed to A R Fielder.

At least 55 records · Page 3Linked to original sources
PubMed1996

Does stereopsis matter in humans?

Stereopsis has been one of the most popular fields of vision research for well over a century and is routinely measured in clinical practice, yet its functional significance has been largely neglected. Stereopsis is disrupted by blur, amblyopia and strabismus and is of potential value as a means of indirect screening for visual disorders in childhood. However, evidence for the functional effects of stereoscopic deficits is sparse. Recent investigations indicate that binocularity is an advantage in certain tasks, especially in the comprehension of complex visual presentations and those requiring good hand-eye coordination. The assumption derived from the evolutionary theory that stereopsis represents an adaptation by primates to arboreal life needs to be questioned. While the functional aspects of stereopsis are still not fully understood the direction that future research should take to unravel this important issue is apparent.

Adult↗
PubMed1996

Geographical variations in rates of ophthalmic surgery.

AIMS/BACKGROUND: Geographical variations in health care are common. There is, however, no simple explanation for why they arise. Variations in rates of ophthalmic surgery in the population aged 65 and over were investigated, with the aim of determining their cause. METHODS: Routine data sources were used to obtain the 1991-2 age and sex standardised rates for English health districts with an ophthalmic unit. Weighted least squares regression was used to study the relation between these rates and various factors describing the population and the provision of care. RESULTS: Surgery rates varied more than threefold. High rates of surgery were associated with high throughput and bed numbers (both p < 0.001), high proportions of day case surgery (p < 0.001), long waiting lists (p < 0.001), and a high number of theatre sessions (p = 0.002). Conversely, a high percentage of emergency admissions was associated with lower rates of surgery (p = 0.004). These six variables accounted for 58% of the variation. CONCLUSION: Geographical variations were found to exist, less than two thirds being explained by differences in the provision of care. The remaining variation may partly be attributed to private practice and the lack of consensus for many ophthalmic procedures (the 'surgical signature'), including a lowering of the threshold for surgery. These findings have implications for the planning of ophthalmic services.

Aged↗
PubMed1995

Multidisciplinary teams and childhood visual impairment: a study of two teams.

Multidisciplinary teams are generally viewed as beneficial in the management of the visually impaired child, yet little is known about them. Two teams were studied. Team A had well-defined functions relating to identification of visually impaired children, co-ordination of services and liaison. Team B had a more general aim of sharing information on a range of ophthalmic issues other than visual impairment. By comparing the two teams, we conclude that a multidisciplinary team is more likely to be effective if it draws its membership from a range of appropriate professions and its functions are focused. Benefits of teams include increased and earlier referral, improved interdisciplinary liaison and collaboration, and speedier and more appropriate implementation of services. Lack of time to participate, particularly by medical personnel, is a problem.

Child↗
PubMed1995

Compliance in amblyopia therapy: objective monitoring of occlusion.

AIM/BACKGROUND: This study aimed to determine the feasibility of objective compliance monitoring of amblyopia therapy in clinical research. Occlusion has been the mainstay of amblyopia therapy for over 250 years, yet it has never been subjected to rigorous evaluation. Treatment regimens range arbitrarily from a few minutes to most of the waking hours of the day. Compliance is problematic and as, hitherto, accurate objective monitoring has been impossible it is not known how much occlusion is required to effect an improvement in vision. METHODS: An occlusion dose monitor (ODM) has been developed. The ODM consists of a modified occlusion patch and a miniature battery driven datalogger which periodically monitors patch skin contact. The patch is a standard disposable item with two miniature electrocardiogram electrodes attached to its undersurface. The datalogger comprises a high speed static RAM and a clock driven address counter. Data are retrieved using an IBM PC/AT computer. Fifteen child amblyopes were randomly allocated unilateral occlusion of 1, 4, or 8 hours per day for 4 weeks. Owing to data loss, presumed because of accumulation and discharge of static electricity, an additional child was included in the 8 hour group. Outcome measures were objective (ODM) and subjective (diary) compliance with treatment, logMAR visual acuity, and contrast sensitivity. RESULTS: Objective monitoring of occlusion is technically feasible and clinically informative. CONCLUSION: Objective monitoring of occlusion has opened up new research opportunities which, it is hoped, will enable the dose-effect relation of occlusion therapy in the various types of amblyopia to be investigated objectively, and facilitate the design of effective therapeutic regimens.

Amblyopia↗
PubMed1994

Patterns of professional involvement with parents of visually impaired children.

The authors sampled a range of professionals who deal with visually impaired children to determine how they involve parents in the management of these children. There were 10 peripatetic teachers, eight ophthalmologists, six paediatricians, three social workers, three headmasters of special schools for visually impaired children, and two educational psychologists. Ophthalmologists were the least likely to attend multidisciplinary case discussions, involve parents in discussions or give parents written information. About half the sample presented an optimistic picture, but almost half considered that parents needed more support, more information or improved communication between professionals. Two complementary solutions are proposed: the development of multidisciplinary teams and the use of a 'key person' or 'case manager' to co-ordinate services.

Adult↗
PubMed1994

Unrecognised and unregistered visual impairment.

Recent community based studies have shown that only a minority of visually impaired people who are eligible to be registered as partially sighted or blind are actually registered as such. To determine how many unregistered but eligible people are attending ophthalmic clinics a prospective study was undertaken of all patients (n = 1543) attending ophthalmic outpatient departments, at a single specialty eye hospital and two district general hospitals over a 1 week period. All patients with visual acuity < or = 6/18 or restricted visual field were interviewed. Registration status and factors affecting this were then determined. Although 95/174 patients interviewed were eligible for registration, 68 as partially sighted and 27 as blind, only 46 (48.4%) of these were registered. Asians and Afro-Caribbeans were under-represented in the group eligible for registration. Active treatment impeded registration. Patients having four or more hospital visits were on average 16 times more likely to be registered as those who had fewer attendances. Disabilities, in addition to visual impairment, were present in 40% (n = 38). This study shows that there is unregistered visual impairment in patients attending ophthalmic departments. As registration triggers multidisciplinary support, ophthalmologists need to be more alert to the benefits and criteria for partial sight and blind registration.

Adolescent↗
PubMed1994

Visual acuity and pupillary responses to spatial structure in infants.

PURPOSE: To determine the age of onset of the pupil grating response (PGR). To compare estimates of resolution acuity obtained by pupillometric and behavioral methods in early infancy. METHODS: Dynamic infrared pupillometry was undertaken on 19 newborn infants while they fixated a uniform background upon which a 0.1 c/deg sine wave grating was briefly presented. Pupillary responses were also recorded to an increment in luminance of a spatially homogeneous target. Longitudinal measurements of PGRs were obtained from a subset of eight infants between 3.5 and 38 weeks of age. In this group, behavioral estimates of visual resolution obtained using the acuity card procedure were compared with the highest spatial frequency grating to elicit a PGR. RESULTS: When presented with the pattern stimulus, newborn infants did not show any pupil reaction indicative of a PGR. This finding could not be attributed to immaturity of pupillomotor function: All infants showed marked pupillary construction to diffuse light stimulation. By 1 month of age, pupillary responses to pattern stimuli were reliably present. For these and older infants, the spatial frequency of the finest grating to elicit a PGR was comparable to the behaviorally determined resolution threshold: mean difference (+/- 95% confidence interval) = 0.28 +/- 0.23 octaves. CONCLUSIONS: A PGR could not be detected in newborn infants. From 1 month of age, responses to spatial structure can provide objective estimates of visual acuity comparable to those determined by established methods.

Age of Onset↗
PubMed1993

Comparison of the Keeler Pulsair 2000 non-contact tonometer with Goldmann applanation.

The Pulsair 2000 non-contact tonometer (Keeler Ltd, UK) is compared with the Goldmann applanation tonometer. Data from 80 eyes were acquired by four experienced observers. A linear regression analysis showed the relationship between the instruments to be: Pulsair = 0.66 + 0.95 Goldmann. Individual components of variation were analysed by analysis of variance which indicated a significant variation in the slope of the regression equation due to observers (p = 0.02) but not to the order in which topical anaesthesia was administered. Differences between two Pulsair instruments were of marginal significance (p = 0.07). The intercept of the regression equation was unaffected by any of the components of variation. Seventy-nine per cent of averaged intraocular pressure measurements obtained with the Pulsair 2000 fell on or within +/- 3 mmHg of those measured with the Goldmann tonometer. It is concluded that the Pulsair 2000 can provide clinically useful measurements of intraocular pressure.

Adolescent↗