Day surgery for cataracts.
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Ambulatory Surgical Procedures↗
Biomedical subjects
A R Fielder
Publications and source records attributed to A R Fielder.
Light and the neonatal eye.
The lighting environment where the baby born prematurely is placed is different from that experienced in utero. As early exposure to light may affect the immature visual system we have attempted to quantify the neonatal ocular light dose. Lighting surveys performed in 7 neonatal units (NNUs) suggested that mean unit illuminance was 470 lux (range 192-890 lux) and intensive care areas within the NNU were significantly brighter than their corresponding low dependency nurseries. The spectral power distribution of fluorescent lights in NNUs was weighted towards the blue end of the spectrum. Datalogging studies demonstrated that between about 30% and 98% of environmental light was incident on the eyelid, which acts as a predominantly red-pass filter, permitting 21% transmission at 700 nm with less than or equal to 5% transmission at 580 nm. Eye-lid opening frequency was quantified: 45% less than or equal to 26 weeks gestational age and decreasing to 7% at 28 weeks gestational age. The onset of the pupillary reflex to light was between 30 and 34 weeks postmenstrual age, the mean diameter was 3.46 mm before this event and 3.02 mm afterwards. Retinal irradiance values calculated from these data show that it is a function of postmenstrual age. Further studies are required to determine its effect on the immature visual system.
Eye↗
Mitochondrial abnormalities in the DIDMOAD syndrome.
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Adolescent↗
Retinopathy of prematurity: a prospective study. Review at six months.
A cohort of infants of birthweight < or = 1700 g studied prospectively for retinopathy of prematurity (ROP) has been reviewed at 6 months corrected age and the findings related to the neonatal data. The overall incidence of strabismus was 6.4% (30/468), rising from 3.1% (7/229) without ROP to 29.2% (7/24) with stage 3. Strabismus and fusional ability were significantly related to presence and severity of ROP, and abnormal neonatal cranial ultrasound findings. Binocular visual acuity was measured in 340 infants between 20 and 40 weeks corrected age. Eight were subnormal, all due to neurological problems. For the remainder, despite falling within the normal range, there was a significant trend (p < 0.001) for lower acuities with increasing ROP severity. Cycloplegic refraction on 387 infants revealed, with increasing ROP severity: 1, a significant trend towards myopia; 2, increased magnitude of astigmatism; 3, alteration of the astigmatic axis; 4, increased incidence of anisometropia. For the first three categories there was an insignificant trend between no ROP and stage 2, reaching significance only between stage 2 and 3. The predominant axis of astigmatism in infants without ROP was between 60 degrees and 120 degrees, but with ROP there was a significant trend away from this direction.
Age Factors↗
Light and the immature visual system.
Preterm neonates are cared for in an environment which is continuously and brightly lit, and is very different to that experienced at any other time of life. The amount of light reaching the neonatal eye is governed by two groups of factors. Physical factors include intensity, spectral characteristics and duration of light exposure. Physiological factors are: Frequency of eyelid opening, transmission of light through the closed eyelid, pupil reactivity and area, transmission by the ocular tissues and retinal surface area. Retinal irradiance declines with increasing postmenstrual age. Mechanisms by which light may affect the neonatal eye and clinical conditions in which light have been implicated are considered.
Dose-Response Relationship, Radiation↗
Natural history of retinopathy of prematurity: a prospective study.
The natural history of retinopathy of prematurity (ROP) has been studied prospectively in 572 infants < or = 1,700 g birthweight using a protocol designed specifically to investigate the subtle features of this condition. Acute ROP developed in 50.9%. All ROP stages 1 and 2 underwent complete resolution and of the 27 (4.7%) infants with stage 3/4 disease, cicatricial sequelae developed in six. Incidence and severity increased with decreasing birthweight and gestational age. Onset was not confined to the temporal retina but exhibited a predilection to start first in the nasal retina of the most immature neonate. The vertical retinal regions were relatively spared. Retinal arteriolar tortuosity developed around three months postnatally and was related to ROP severity but not its presence. The age at onset and rate of progression of retinopathy were largely determined by the stage of development but were also modified by systemic and local factors. The relevance of these findings to ROP screening is discussed.
Acute Disease↗
Screening for retinopathy of prematurity.
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Cryosurgery↗
Current practice of cataract extraction and anaesthesia.
A questionnaire regarding preferred methods of cataract extraction and anaesthesia was sent to 456 consultant ophthalmologists in England and Wales. Replies were received from 86% (n = 392), 83% (n = 380) having completed the questionnaire in full. The most frequently employed surgical approach was non-automated extracapsular cataract extraction. Only 2% of surgeons (n = 8) used phacoemulsification routinely and 2% (n = 7) used intracapsular extraction. Intraocular lens implantation was the standard practice of 99% of surgeons (n = 376). There has been a dramatic increase in the popularity of local anaesthesia, which was employed routinely (in more than three-quarters of their cases) by 20% of surgeons (n = 76). Retrobulbar infiltration remains the most common method of administration. Sedation was given routinely by 45% of surgeons (n = 171) when using local anaesthesia. Medical contraindications and patient preference were considered the most important reasons for selecting local anaesthesia rather than general. The exclusive use of general anaesthesia in cataract surgery appears to be diminishing.
Age Factors↗
Preferential looking--clinical lessons.
Preferential looking-based tests of acuity have been available for over a decade. The authors discuss their use in clinical practice, particularly in three groups in whom acuity could not be quantified by traditional means: normal infants, and young children who are either mentally retarded, or who have visual disorders. Preferential looking (PL) testing has increased our understanding of the natural history of visual pathway disorders and has revealed certain patterns of acuity development. Early acuity development may be normal, delayed, or stationary, while in later infancy and childhood the following abnormal patterns have been identified: asymptotic, parallel, catch-up, or regressing. While this information has introduced a degree of complexity hitherto unknown which, if misunderstood, can lead to test misinterpretation, it offers the clinician invaluable information to improve patient care, and may also offer clues to the fundamental mechanisms of visual development.
Child, Preschool↗
Light and retinopathy of prematurity: does retinal location offer a clue?
Nursery illumination has been implicated in the pathogenesis of retinopathy of prematurity (ROP), although the results of recent studies are conflicting. The data base for this article is a prospective ROP study on 607 infants of birth weight less than or equal to 1700 g including 35 larger siblings from multiple births when 1 infant fulfilled the birth weight criteria. Retinopathy commences preferentially in the nasal retina of the most immature neonate and is less likely to develop, or its onset is delayed, in the superior and inferior regions. These findings cannot be fully accounted for by regional vascular and neuroanatomical variations. Radiometric and physiological evidence suggests that the very immature neonate, most at risk of developing severe ROP, receives the greatest retinal irradiance. Furthermore, ROP commences in the areas of the retina receiving the highest light dose, and its onset is either retarded or inhibited in the darker retinal regions. Further studies are required to determine whether early exposure to light is a factor in the development of ROP. If a causal relationship is proven, here at least is one modality that can easily and immediately be controlled.
Cohort Studies↗
Delayed visual maturation.
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Child, Preschool↗
Transmission of light across the adult and neonatal eyelid in vivo.
Light transmission characteristics of the human adult and neonatal eyelid were measured in vivo. Light was delivered via a grating monochromator through a fibre-optic mounted onto a contact lens placed under the eyelid, and detected using a photodiode on its external skin surface. Data from 5 adult and 9 preterm neonatal subjects indicate that the eyelid acts as a predominantly red-pass filter, with mean transmissions at 700 nm of 14.5% in the adult and 21.4% in the neonate, declining to less than or equal to 3% in both groups below 580 nm. The relevance of this data to clinical electrophysiology and to estimates of retinal irradiance is discussed.
Adult↗
Visual development of infants with severe ocular disorders.
Among 11 patients who presented as blind in early infancy, with Leber's congenital amaurosis (5 patients), optic nerve hypoplasia (4 patients), or macular colobomata (2 patients), 8 developed visually guided behavior and measurable grating acuity by age 5 to 46 months. All children with measurable grating acuity demonstrated visually guided mobility. Grating acuity was predictive of later visual performance in 10 of 11 patients by age 12 to 16 months. The best grating acuity attained by 7 months was 1.3 to 3.0 cycles/degrees (20/460 to 20/200) and 0.13 cycles/degrees (20/4700) by month 8. Two patients with Leber's congenital amaurosis and one with optic nerve hypoplasia remained blind. No clinical features existed to differentiate these three patients from the eight whose visual status improved. Posterior visual pathway maturation may underlie the improvement.
Child↗
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↗
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↗
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↗
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↗