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Biomedical subjects

A R Fielder

Publications and source records attributed to A R Fielder.

At least 91 records · Page 5Linked to original sources
PubMed1991

Light transmission measurements and phototherapy eyepatches.

The transmission characteristics of phototherapy eyeshields have been measured under conditions that mimic the clinical situation. Peak transmission (less than 10%) was detected at 700 nm for the poorest patch tested and less than 2% for either of the other patches examined. The optics of measurement systems are considered with reference both to this and previous studies of light transmission through eyepatches. The simplicity and effectiveness with which eyepatches can be secured may be as important as their transmission characteristics.

Evaluation Studies as Topic↗
PubMed1990

Ophthalmic findings in infants of very low birthweight.

The ophthalmic findings in 127 very low-birthweight infants seen at a mean corrected age of 7.6 months (range one to 15 months) are presented and related to their neonatal findings on cerebral ultrasound scanning and eye examinations for retinopathy of prematurity. 19 infants (15 per cent) had significant ophthalmic abnormalities, including reduced visual acuity (11), squints (13), disorders of supranuclear eye-movement (three) and retinal abnormalities (eight). A strong association was found between cystic periventricular leukomalacia and ophthalmic morbidity.

Brain Diseases↗
PubMed1990

Pupillary diameter and reaction to light in preterm neonates.

The pupil controls the amount of light entering the eye. We have examined both the time course for the development of the light reflex and pupil diameter before and after this event in 50 neonates. The pupillary light reflex was absent in all neonates of less than 30 weeks' gestational age, it gradually developed from this age and by 35 weeks it was present in all. Several possible mechanisms that may explain the onset of this reflex are considered. Before the onset of the pupil reflex mean horizontal pupillary diameter was 3.46 mm compared with 3.02 mm after the reflex development. We have estimated the amount of light reaching the retina (retinal irradiance) for preterm neonates and although it is less than that known to cause retinal damage in animals, further research is necessary to determine whether early light exposure has an adverse or beneficial effect on the immature visual system.

Female↗
PubMed1990

Illuminance of neonatal units.

We have measured the illuminance (brightness) of seven neonatal units during both the day and the night. When the units were lit solely by fluorescent tubes the mean illuminance was 348 lux (range 192-690). During the day the mean illuminance was 470 lux (range 236-905). The high dependency regions in four of the seven units were significantly brighter than the corresponding low dependency nurseries at all times. In two of these units there is a policy of reducing the amount of artificial light in the low dependency areas at night, and in these the normal mean illuminance was 50 lux. We have measured the general levels of illumination to which a neonate might be exposed; the ocular exposure to light of a neonate depends, however, on both physical and biological factors and more research is required before an accurate estimate can be made.

Humans↗
PubMed1990

Ocular findings in Angelman's (happy puppet) syndrome.

Patients with Angelman's syndrome have been reported to have ocular hypopigmentation and a number are now known to have a microdeletion of chromosome 15q 11----13. Detailed ocular examination of eight new cases revealed normal visual acuity and foveal reflexes, but a pigmentary deficiency which is limited to the choroid and iris stroma--both of neural crest origin. Patients with Prader-Willi syndrome have similar ocular features and many have a microdeletion of chromosome 15q 11----13. It is therefore possible that this region may influence neural crest development.

Abnormalities, Multiple↗
PubMed1990

Delayed visual maturation: ophthalmic and neurodevelopmental aspects.

Delayed visual maturation (DVM) can present as an isolated anomaly (type 1A), but can be compounded by perinatal problems (type 1B), severe neurodevelopmental delay (type 2), or ocular anomalies/nystagmus (type 3), in which group the common feature appears to be nystagmus. The neurodevelopmental and ophthalmic aspects of 26 infants with DVM were studied. Onset of visual improvement, rate of acquisition of normal vision and eventual outcome were studied quantitatively, using an adaptation of the acuity card procedure. Neurodevelopmental assessment was performed after visual improvement. The results support the long-held clinical impression that if blindness is the presenting feature, neurodevelopmental outlook is excellent. DVM could represent a defect in the extrageniculostriate visual system, and the onset of vision in all types--and the development of nystagmus in type 3--could herald the emergence of geniculostriate function.

Blindness↗
PubMed1990

Congenital double elevator palsy in identical twins.

A left-sided double elevator palsy in identical twins born prematurely is presented, the first such report in twins. The aetiology of this condition is considered, and given the preservation of Bell's phenomenon and the absence of hypotropia in the primary position, the possibility that this may represent a supranuclear defect is discussed.

Diseases in Twins↗
PubMed1989

Comparison of a new non-contact tonometer with Goldmann applanation.

A comparison of a new non-contact tonometer (Keeler Pulsair: Keeler UK Ltd) with the Goldmann applanation tonometer is reported. Measurements of intraocular pressure were obtained from 182 eyes of 94 patients. At low pressures (less than 10 mmHg) the candidate tonometer tended to overestimate pressures obtained with the Goldmann tonometer whilst at high pressures (greater than 19 mmHg) those obtained by Goldmann applanation were underestimated. Between 10 and 19 mmHg there was no significant difference between readings obtained with either method. Up to 71% of averaged Pulsair measurements fell within +/- 3 mmHg of those obtained with the Goldmann tonometer increasing to 78% if pressures greater than or equal to 30 mmHg obtained with the Pulsair tonometer were excluded. Adopting a screening criterion of greater than or equal to 21 mmHg (Goldmann) resulted in a sensitivity of 85% and a specificity of 95%. Some evidence that serial Pulsair readings are influenced by the ocular pulse is presented. It is concluded that the Pulsair tonometer can provide clinically useful measurements of intraocular pressure.

Evaluation Studies as Topic↗
PubMed1989

Eyelid opening in preterm neonates.

The frequency and patterns of eyelid opening were examined in a group of neonates (gestational age 24-35 weeks). Observations were spread over the 24 hour period to obtain a complete pattern of events. Mean eyelid closure was 74%. When babies were grouped by gestational age, however, differences became apparent, babies of less than 26 weeks having their eyes shut for only 55% of observations compared with 93% at 28 weeks. Trend analysis confirmed that eyelid closure reached a peak at 28 weeks. Neonates exposed to a day/night regimen, opened their eyes significantly more than those exposed to continuous illumination. We suggest that frequency of eyelid opening may be related both to the infant's developmental state (postmenstrual age) and the illumination of the neonatal unit. Frequency of eyelid opening should therefore be considered when calculating the ocular light exposure of preterm neonates.

Aging↗
PubMed1989

Spontaneous recovery of vision following an orbital haemorrhage.

A 73-year-old man presented to casualty with a penetrating orbital injury and total loss of vision in the affected eye. He subsequently spontaneously recovered full vision. We stress the need for frequent assessment of vision before considering potentially hazardous surgical intervention.

Aged↗
PubMed1989

Are severe acute retinopathy of prematurity and severe periventricular leucomalacia both ischaemic insults?

Over a period of 20 months six preterm infants have been seen who developed severe acute retinopathy of prematurity (ROP) and who also had ultrasound evidence of extensive cerebral parenchymal changes compatible with severe periventricular leucomalacia. Only one of these infants had a birthweight of less than 1000 g, and their gestational ages ranged from 27 to 30 weeks. The association between these two important complications of preterm birth has led us to postulate that an episode of hypoperfusion of the cerebral circulation sufficient to result in cerebral ischaemia could also reduce an already compromised ocular blood flow and further exacerbate retinal ischaemia, thereby increasing the severity of ROP.

Brain Ischemia↗
PubMed1989

Validation of a photographic method of measuring corneal diameter.

A photographic method for measuring corneal diameter using the Medical-Nikkor f200 mm lens is described. Measurements were compared with those obtained by calipers (46 eyes of 25 patients) and by placing a ruler either near the eye (123 eyes of 64 patients) or on the nose (98 eyes of 55 patients). Over all we found good correlation between photographic and caliper measurements (r = 0.94). No significant correlation was found between photographic measurements and estimates made with the ruler either near the eye or on the nose (r = 0.65 and 0.31 respectively). Modifications to our system are suggested which may provide an accurate, simple, non-invasive method of measuring corneal diameter in ophthalmic clinics.

Adult↗
PubMed1988

Epidemiology of retinopathy of prematurity.

The incidence and severity of retinopathy of prematurity (ROP) were studied prospectively in a geographically defined area of the East Midlands. Over 23 months, 505 infants weighing 1700 g or less at birth to mothers resident in this area were studied. Acute ROP developed in 248 (49.1%) and there was a significant association between short gestation and low birthweight and greater severity. Most acute ROP underwent complete resolution; only stage 3/4 disease did not and cicatricial sequelae subsequently developed in 5 infants, 23.8% of this group. No infant was blind because of ROP. Black infants had shorter gestations yet were less likely to have any stage of ROP. Although Asians were not smaller than their caucasian counterparts, severe (stage 3/4) ROP was more likely (14.1% vs 2.7% for caucasians); this difference was largely due to their better survival. Since 505 of the available 547 infants in this geographically defined area were examined, it was possible to calculate the incidence of acute and cicatricial ROP on a community population basis. There are dangers in attempting to deduce the incidence of acute ROP from infrequent eye examinations, and in comparing community and hospital-based reports.

Acute Disease↗
PubMed1988

Amblyopia--factors influencing age of presentation.

In the 47 months from September, 1981, 1531 new cases of amblyopia were identified in the ophthalmic clinics of Leicestershire. Amblyopia was due to strabismus in 689 (45%), combined strabismus and anisometropia in 540 (35%), anisometropia alone in 252 (17%), and form deprivation in 50 (3%). The median age at presentation for strabismic amblyopia (3.64 years) was significantly lower than for combined strabismus and anisometropia (4.68 years) and anisometropia (6.27 years). Boys presented later than girls, as did Asians compared with Caucasians. Only 38 (15%) of children with a visual defect without strabismus (anisometropia) were identified before the age of 5 years. The major reason for this late identification is the lack of a reliable single test for preschool vision assessment.

Adolescent↗
PubMed1988

Effects of nursery illumination on frequency of eyelid opening and state in preterm neonates.

The behaviour of a group of premature neonates was observed under three conditions of ambient illumination defined as either DARK, LIGHT or BRIGHT (mean intensities: 0.9, 109 and 1370 lux). Trends in the data suggested that increasing the level of illumination resulted in a reduction in the proportion of time spent with eyelids open and of the amount of time spent in awake states. However, these effects were small and in most cases failed to attain statistical significance. Sudden offset of light did however produce a transitory increase in eyelid opening for a period of approximately 60 s that appeared to be unaccompanied by any change of state (P less than 0.001). Irrespective of illumination condition, the infants' behaviour was characterized by prolonged periods of eyelid closure which were significantly greater for the lower eye (in mattress contact, mean lid closure = 96.2%) compared to the upper eye (no mattress contact, mean lid closure = 88.25%). The prolonged occurrences of eyelid closure are discussed in relation to visual development and phototoxicity.

Arousal↗