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Biomedical subjects

A R Fielder

Publications and source records attributed to A R Fielder.

At least 37 records · Page 2Linked to original sources
PubMed2002

Design of the Monitored Occlusion Treatment of Amblyopia Study (MOTAS).

BACKGROUND/AIMS: The effectiveness of occlusion therapy for the treatment of amblyopia is a research priority. The authors describe the design of the Monitored Occlusion Treatment for Amblyopia Study (MOTAS) and its methodology. MOTAS will determine the dose-response relation for occlusion therapy as a function of age and category of amblyopia. METHODS: Subjects progress through up to three study phases: (1) Assessment and baseline phase: On confirmation of eligibility, and after parental consent, baseline visual functions are determined, and spectacles prescribed as necessary; (2) Refractive adaptation phase: Subjects wear spectacles full time and return to clinic at 6 weekly intervals until 18 weeks, by which time all improvement due to refractive correction is complete; (3) Occlusion phase: All subjects are prescribed 6 hours of occlusion per day. Daily occlusion is objectively monitored using an occlusion dose monitor (ODM). OUTCOME VARIABLES: visual acuity (logMAR charts), log contrast sensitivity (Pelli-Robson chart), and stereoacuity (Frisby) are assessed at 2 weekly intervals until gains in visual acuity cease to be statistically verifiable. CONCLUSION: Four methodological issues have been addressed; firstly, baseline stability of visual function; secondly, differentiation of refractive adaptation from occlusion; thirdly, objective measurement of occlusion dose and concordance; fourthly, use of validated outcome measures.

Amblyopia↗
PubMed2001

Retinopathy of prematurity: clinical aspects.

There have been many major advances recently that have improved the identification and management of retinopathy of prematurity (ROP). This chapter describes the clinical features of ROP and then considers briefly the incidence and epidemiology of acute phase disease. This is followed by a discussion of the two ROP epidemics and ROP-induced disability in high, low and middle income countries, and how this has been impacted by treatment. The principles and specifics of screening for ROP are considered, focusing on certain topical issues such as whether one screening guideline suits all populations. Treatment has undergone several advances, so that now laser therapy has overtaken cryotherapy as the preferred mode of treatment, and treatment at an earlier stage is now being considered. Finally, the authors attempt to look into the future and wonder how the criteria for treatment will change, and whether innovations in ocular imaging will impact ROP screening in both high and middle income countries.

Disease Outbreaks↗
PubMed2001

Reduced lighting does not improve medical outcomes in very low birth weight infants.

OBJECTIVE: To objectively assess the effect of light reduction as an isolated environmental intervention on neonatal morbidity. STUDY DESIGN: Randomized multicenter trial. Neonates < 1251 g birth weight and < 31 weeks gestational age were randomly assigned to receive goggles or to a control group. Goggles that reduced visible light by 97% were placed within 24 hours of birth and remained in use until 31 weeks postmenstrual age or for a minimum of 4 weeks. RESULTS: Four hundred nine infants were enrolled, and outcome data are reported for 359 surviving infants. There were no significant differences between the groups in weight gain, duration of oxygen therapy, mechanical ventilation, or hospital stay either in the unadjusted analyses or in the analyses adjusted for birth weight, gestational age, race, sex, and inborn (born in study hospital) status. There was no difference between the groups in the incidence of intracranial hemorrhage. CONCLUSIONS: This randomized trial of continuous light reduction in the first few weeks of life for very low birth weight infants showed no effect on medical outcomes.

Child Development↗
PubMed2000

Environmental light and the preterm infant.

The lighting environment of the preterm baby is quite unlike that experienced at any other time of life. Physical and physiological factors control how much light reaches the retina of the preterm baby. With respect to the former, although many neonatal intensive care units are brightly and continuously lit, there is a trend to employ lower levels of illumination and to introduce cycling regimens. Physiological determinants of the retinal light dose include: eyelid opening and transmission, pupil diameter and the transmission characteristics of the ocular media. Early exposure to light does not significantly hasten or retard normal visual development, and it is not a factor in the development of retinopathy of prematurity. However, ambient neonatal intensive care unit illumination may be implicated in some of the more subtle visual pathway sequelae that cannot be attributed to other major complications of preterm birth including altered visual functions and arrested eye growth.

Animals↗
PubMed2000

Severe retinopathy of prematurity and its association with different rates of survival in infants of less than 1251 g birth weight.

BACKGROUND: There is controversy over whether improved survival of preterm infants has resulted in a higher incidence of severe (grade 3 or greater) retinopathy of prematurity (ROP). AIM: To compare survival rates and rates of > or = stage 3 ROP-that is, with a high risk of sequelae-in preterm infants in five English cities where, anecdotally, the incidence of ROP is reported to show considerable variation. METHODS: All infants of birth weight < 1500 g and or gestational age < 32 weeks, born in 1994 in one of the cities or transferred in within 48 hours, were studied. The populations were adjusted for case mix variation using CRIB (clinical risk index for babies, a disease severity scoring system). The incidence of severe ROP, the actual death rate, and that adjusted for disease severity were determined. RESULTS: The rate of severe ROP per 1000 births was higher in city 1 than in all the other cities. This increase in comparison with city 2 and city 4 was significant (city 1, 167 (95% confidence interval (CI) 96 to 260); city 2, 24 (6 to 59); city 4, 16 (1 to 84)). A significant difference was not seen between city 1 and cities 3 (23 (1 to 120)) and 5 (74 (21 to 79)). The relative risk of developing severe ROP in city 1 compared with all the other cities was 5.5 (2.5 to 11.9). The actual death rate per 1000 births in city 1 was significantly lower than that predicted by modelling death against CRIB score (city 1: actual 270; predicted 385 (95% CI 339 to 431)). In contrast, the other cities had actual death rates as predicted, or worse than predicted, by CRIB. INTERPRETATION: A significantly higher incidence of severe ROP was identified in one of the five cities studied. Variation in survival rates among high risk infants may explain this observation.

England↗
PubMed1998

Lack of efficacy of light reduction in preventing retinopathy of prematurity. Light Reduction in Retinopathy of Prematurity (LIGHT-ROP) Cooperative Group.

BACKGROUND: Hospital-nursery lighting has been suggested as a factor in causing retinopathy of prematurity. Despite ongoing debate, a causal relation has not been established. METHODS: We conducted a prospective, randomized, multicenter study of the effects of light reduction on 409 premature infants with birth weights of less than 1251 g and gestational ages of less than 31 weeks. Two hundred five infants were exposed to reduced light, and 204 to typical nursery lighting. The amount of light reaching the infants' eyes was reduced within 24 hours after birth by placing goggles on the infants that reduced visible-light exposure by 97 percent and ultraviolet-light exposure by 100 percent. The babies wore the goggles until 31 weeks' postconceptional age or 4 weeks after birth, whichever was longer. Once the goggles were removed, ophthalmologists masked to the treatment assignments assessed the infants for retinopathy of prematurity at least biweekly for up to 13 weeks. RESULTS: There were 188 infants in the group that wore goggles and 173 in the control group who survived and were available for follow-up. The mean birth weights were 906 g in the goggles group and 914 g in the control group; the mean gestational ages were 27.4 weeks and 27.2 weeks, respectively. The mean ambient-light level adjacent to the infants' faces was 399 lux for the goggles group and 447 lux for the control group. Retinopathy of prematurity was diagnosed in 102 infants (54 percent) in the goggles group and 100 (58 percent) in the control group (relative risk, 0.9; 95 percent confidence interval, 0.8 to 1.1; P=0.50). CONCLUSIONS: A reduction in ambient-light exposure does not alter the incidence of retinopathy of prematurity.

Eye Protective Devices↗
PubMed1998

Delayed visual maturation: pupillary responses implicate subcortical and cortical visual systems.

Vision in very early infancy is probably subserved by subcortical pathways, with many cortical processes only fully emerging by 3 months of age. The improvement of vision in delayed visual maturation (DVM) occurs around this time, and this has given rise to the suggestion that the condition may have a subcortical basis that resolves with the appearance of cortical function. To explore further the role of cortical and subcortical visual systems in DVM we studied the visual development in identical twins, one of whom had type 1b DVM. Two non-invasive methods of investigating visual pathway function were employed: the acuity card procedure (a behavioural response) and luminance and grating pupillometry. While the former reflects both subcortical and cortical function and can be detected at birth, pupil responses to gratings reflect cortical activity alone and normally become measurable at 1 month of age. Development of both behavioural and pupillary responses was delayed in DVM, indicating that although the underlying defect is primarily subcortical, secondarily it delays the emergence of cortically mediated responses. The observed rapidity of improvement--over a very few days and within a narrow age range--suggests a discrete rather than a widespread structural abnormality, the improvement of which is closely linked to postmenstrual age.

Failure to Thrive↗
PubMed1997

Are we screening too many babies for retinopathy of prematurity?

A retrospective, hospital-records-based study of neonates screened for retinopathy of prematurity (ROP) was undertaken to determine whether the inclusion criteria for screening could have been safely altered to reduce the numbers of babies screened whilst not missing any stage III disease. Babies from six neonatal intensive care units in Birmingham were screened by a single examiner. Between November 1989 and November 1995, 1611 babies were examined and 1429 of these fell within the inclusion criteria of current guidelines for ROP screening produced by the Royal College of Ophthalmologists and the British Association of Perinatal Medicine--any baby < or = 1500 g birthweight or < or = 31 weeks gestational age. Thirty-nine (39) babies developed stage III ROP of which 31 (2.2%) were from Birmingham. In addition 8 babies with stage III ROP were referred from elsewhere. All 39 babies with stage III ROP had a birthweight < or = 1250 g or a gestational age of < or = 29 weeks, but 2 fell outside one criterion, indicating the need for both to be used. Had these inclusion criteria been utilised during this period, then 30% fewer babies would have been examined (432 of 1429). The importance of using both birthweight and gestational age as inclusion criteria is discussed, and the dangers of altering the indications for national screening on the basis of one study population is emphasised.

Birth Weight↗
PubMed1997

Optic atrophy in Wolfram (DIDMOAD) syndrome.

Wolfram syndrome is the association of diabetes mellitus and optic atrophy, also called DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy and deafness). Incomplete characterisation has caused diagnostic confusion; we therefore undertook a nation-wide cross-sectional case finding study. We identified 45 patients with Wolfram syndrome, median age 29 years. All patients fulfilled the ascertainment criteria (juvenile onset diabetes mellitus and optic atrophy). Optic atrophy presented in 38 patients with reduced visual acuity and colour vision defect (median age 11 years), progressing to visual acuity of 6/60 or less in 35 patients (median time 8 years, range 1-25 years). Visual field examinations recorded before acuity deteriorated showed central scotomas with peripheral constriction. Blind patients had absent pupillary reflexes. Horizontal nystagmus was seen in patients with other signs of cerebellar degeneration. There was no pigmentary retinal dystrophy; only 3 patients had background diabetic retinopathy, despite a median duration of diabetes of 24 years. Electroretinography was normal in 3 patients and showed reduced amplitude in 3 patients; visual evoked responses were abnormal (10/10 patients: reduced amplitude to both flash and pattern stimulation). Magnetic resonance imaging showed generalised brain atrophy with reduced signal from the optic nerves and chiasm. A postmortem brain specimen from one patient revealed atrophy of the optic nerves, chiasm, cerebellum and brainstem. We found no evidence of mitochondrial genome defects or rearrangements. This primary neurogenerative disorder presents with diabetes mellitus and progressive optic atrophy, probably due to pathology in the optic nerve.

Adolescent↗
PubMed1997

Usher syndrome in the city of Birmingham--prevalence and clinical classification.

AIMS: To estimate the prevalence of Usher syndrome in the city of Birmingham, and to establish a database of patients who have been classified into different clinical subtypes essential for future gene mutation analysis. METHODS: Symptomatic cases of Usher syndrome (US) resident in the city of Birmingham in June 1994 were ascertained through multiple sources. Ophthalmic and audiological reassessment together with examination of medical records and patient questionnaires allowed classification of three subtypes, US 1, US 2, and US 3. In addition, family pedigrees were examined and blood was taken from index patients for DNA extraction. RESULTS: In the population aged over 15 years the prevalence was 6.2 per 100 000 population for all US subtypes. The prevalence for US 1 and US 2 was 5.3 per 100 000 population. This is greater than previously reported. In the age group 30-49 years the prevalence approached 1 in 10 000. Clinical classification found 33% US 1, 47% US 2, and 20% US 3. CONCLUSION: This higher prevalence rate and greater frequency of US 2 and US 3 may reflect a more complete ascertainment.

Adolescent↗
PubMed1997

Effectiveness of occlusion therapy in ametropic amblyopia: a pilot study.

AIMS/BACKGROUND: To examine the relative contributions of non-specific (for example, spectacle correction) and specific (that is, occlusion therapy) treatment effects on children with ametropic amblyopia. To assess the importance and practicality of objectively confirming the prescribed occlusion dose. METHODS: Subjects were entered into a two phase trial. In the first ('pretreatment') subjects were provided with spectacle correction and underwent repeat visual acuity (VA) and contrast sensitivity (CS) testing until acuity in their amblyopic eye had stabilised. Subjects then progressed to the second phase ('treatment') in which they underwent direct, unilateral occlusion for 1 hour per day for 4 weeks. Patching was objectively monitored using an occlusion dose monitor. RESULTS: Eight subjects completed the trial, all but one of whom achieved > 80% concordance with the occlusion regimen. Within the pretreatment phase, mean amblyopic eye VA improved by 0.19 log units (p = 0.008) while mean CS gained 0.09 log units (p = 0.01). An identical improvement in mean VA was recorded in the fellow eyes (p = 0.03) while mean CS gained 0.11 log units (p = 0.02). Within the treatment phase, mean VA further improved (0.12 log units, p = 0.009) although this gain had halved by the end of treatment and was no longer statistically significant (p = 0.09). CONCLUSIONS: Visual performance improved significantly during pretreatment whereas further gains seen during occlusion were not sustained. Evaluation of occlusion regimens must take into consideration the potentially confounding influence of 'pretreatment effects' and the necessity to confirm objectively the occlusion dose a child receives.

Amblyopia↗
PubMed1996

ERG and EOG abnormalities in carriers of X-linked retinitis pigmentosa.

The diagnosis of X-linked retinitis pigmentosa (XL-RP) relies on the identification of the female carriers, in whom fundal abnormalities are often minimal and variable. The electroretinogram (ERG) has been reported as abnormal in 54-96% of heterozygote females. This study examines the combined use of electro-oculogram (EOG) and standardised ERG in 31 obligate and 33 non-obligate carriers of XL-RP. In the obligate carrier group, the EOG was abnormal in 13 carriers (41%), the ERG abnormal in 21 carriers (68%) and a combined EOG and ERG abnormality occurred in 24 carriers (77%). An EOG abnormality alone occurred in 2 carriers (6.5%). Fourteen obligate carriers (45%) showed a peak to peak delay of the ERG scotopic b wave, this being a previously unreported phenomenon. Similarly, in the non-obligate carrier group, the EOG was abnormal in 11 carriers (44%) and the ERG abnormal in 19 carriers (73%). The results of this study suggest that the use of both tests, including measurement of the scotopic b wave latency, may increase the carrier detection rate.

Adolescent↗