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Biomedical subjects

D L McCulloch

Publications and source records attributed to D L McCulloch.

10 recordsLinked to original sources
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

Visual function in Rett syndrome.

The authors examined refractive error, pattern onset visual evoked potentials, ocular posture and they performed internal and external eye examinations in 11 subjects with Rett syndrome (aged between four and 24 years) and 18 normal controls (aged between six and 20 years). Substantial refractive errors were common in the Rett syndrome group. Spectacle correction had never previously been worn and glasses were provided where appropriate. No subjects had nystagmus or optic nerve pallor and only one was strabismic. All subjects had recognisable and reproducible pattern-onset VEPs and latencies and amplitudes did not differ significantly from those of the controls. All demonstrated VEP thresholds of at least 24'. In contrast to other populations with profound disabilities, people with Rett syndrome have good function of the afferent visual pathways and, in view of their substantial refractive errors, are likely to benefit from spectacle correction.

Adolescent↗
PubMed1994

Pattern reversal visual evoked potentials following early treatment of unilateral, congenital cataract.

OBJECTIVE: To describe the pattern reversal visual evoked potentials (VEPs) that were used to monitor and quantify early visual development following treatment for dense, unilateral, congenital cataract. DESIGN: Longitudinal prospective study. PATIENTS: Six infants who underwent surgery and contact lens correction before age 5 months and who had good compliance with occlusion therapy throughout the first 3 years of life. RESULTS: Initially, VEPs from aphakic eyes showed marked abnormalities, including small amplitudes, prolonged latencies, missing components, and absent VEPs to small check sizes. Threshold check size was elevated by 3 octaves or more. With part-time occlusion of the opposite eye, VEPs normalized rapidly in the first year, but residual deficits remained to age 4 years when visual acuities were between 20/50 and 20/120 in aphakic eyes. Threshold check size clearly differentiated between aphakic and normal eyes and was the only VEP parameter that was correlated with single-letter visual acuity. Thus, threshold check size had greater clinical use than measures of pattern VEPs based on latency, amplitude, or waveform. CONCLUSIONS: Patients treated for unilateral congenital cataract, who have early surgery and contact lens correction and comply with occlusion therapy, show a period of rapid VEP maturation and have a good visual prognosis.

Aphakia, Postcataract↗
PubMed1993

Unilateral congenital ptosis: compensatory head posturing and amblyopia.

Patients with unilateral congenital ptosis often adopt chin elevation to maintain fusion. This compensatory head posturing has been considered a sign of fusion, thus indicating a low risk for amblyopia. To evaluate this sign, we reviewed the charts of 11 preverbal children with unilateral congenital ptosis who had straight eyes and appropriate compensatory head posturing to maintain binocular vision. Four additional patients with unilateral ptosis and no compensatory head posturing were tested for comparison. All patients had undergone an examination and had been tested by pattern Visual Evoked Potential (VEP) under chloral hydrate sedation. Five of the 11 patients with compensatory head posturing were found to be amblyopic, three moderately so and two severely affected. The four patients without compensatory head posturing were amblyopic. It is our hypothesis that compensatory head posturing allows peripheral fusion even when significant amblyopia is present. Additionally, the clinical sign of a compensatory head turn to maintain binocular vision does not rule out the presence of significant amblyopia.

Amblyopia↗
PubMed1992

Visual evoked potentials in infants and children.

Visual evoked potential (VEP) studies are of great value in a wide variety of pediatric patients, including those with disorders of the sensory visual pathway and those at risk for visual pathway damage. VEPs are simple, non-invasive, and are particularly appropriate for infants and young children who cannot communicate visual symptoms or cooperate for standard vision assessment. VEPs in pediatric patients have the following main purposes: (1) detecting lesions causing dysfunction of the sensory visual pathways (the VEP is a sensitive indicator of subclinical lesions and can be used to differentiate visual impairment from visual inattention in young infants); (2) confirming functional loss when disorders of the visual system are present; (3) quantifying visual impairment in patients with known visual disorders, accomplished either empirically by noting the severity of the VEP abnormality to flash and pattern stimuli or by visual acuity estimation studies (early quantification of vision loss allows referral to early intervention programs, which can ameliorate the long-term consequences of the disability); (4) monitoring patients who are at risk for visual complications either from diseases (such as hydrocephalus or neurofibromatosis) or as a complication of therapeutic intervention (e.g., neurosurgery, chemotherapy) to help detect and avoid long-term sequelae of such therapies on the developing nervous system; (5) establishing prognosis for visual and systemic recovery based on flash VEPs for specific pediatric disorders including perinatal asphyxia in full-term neonates, acute-onset cortical blindness, and, to a fair extent, in comatose children; and (6) in some cases, contributing to the differential diagnosis. Abnormalities of flash and/or pattern VEPs are generally nonspecific to the type of exact location of the lesion, except in distinguishing prefrom postchiasmal lesions. However, in certain conditions, such as the hereditary ataxias of childhood, VEP abnormalities may help in the diagnosis. Similarly, deterioration in VEPs may help differentiate progressive from static encephalopathies. VEPs have become an indispensable tool in pediatric ophthalmology and neurology. They will probably play an increasingly important role in the future, primarily due to the difficulty in assessing visual system function in young or ill children and the VEP's sensitivity to subclinical damage in this aspect of the central nervous system.

Brain Damage, Chronic↗
PubMed1991

Visual evoked potentials and visual prognosis following perinatal asphyxia.

Twenty-five children born at term with perinatal asphyxia were studied at age 2.5 to 4.5 years to evaluate visual function and to determine the prognostic value of postnatal assessments of visual outcome. Postnatal assessments included several visual evoked potentials and electroretinograms in the first week of life. Follow-up assessments included flash and pattern visual evoked potentials, visual evoked potential threshold measurements, and clinical eye examinations. Nineteen children had normal visual function, three were visually impaired, and three remained blind. A strong association was found between normal, abnormal, or absent visual evoked potentials in the early postnatal period and long-term visual outcome (P less than .0001). Other perinatal indicators of asphyxia, including neurologic status, Apgar scores, and arterial pH values, were poor predictors of visual outcome. The risk of visual impairment was limited to those survivors with neurodevelopmental deficits.

Asphyxia Neonatorum↗
PubMed1991

Development of the human visual system: monocular and binocular pattern VEP latency.

Pattern visual evoked potentials (P-VEPs) were recorded in 161 human infants who were between 3 weeks and 2 yr of age. The latency of the first reproducible positive peak in the P-VEP was measured monocularly and binocularly for five sizes of phase alterations checkerboard stimuli (range: 120' to 7.5' check widths). Rapid visual maturation in the first 6 months of life was shown by the development of reproducible P-VEPs to smaller check sizes and by a rapid decrease in the latency of the first reproducible positive peak. Monocular P-VEPs have slightly longer latencies than the binocular P-VEPs. This latency difference is invariant with age, but is significantly greater with larger check stimuli. Normal ranges for this large population are provided as a reference for clinical studies.

Adult↗
PubMedDate not supplied

Prognostic value of VEPs in young children with acute onset of cortical blindness.

Visual evoked potentials (VEPs) were recorded in 32 children (ages 4 months to 5 years) who were clinically diagnosed as being cortically blind. None of the children had visual or neurologic abnormalities prior to the precipitating insult which included surgery (N = 15), trauma (N = 3), infectious disease (N = 5), hypoxia (N = 3), and other causes (N = 6). VEPs were recorded during the acute stage of cortical blindness in all children and were repeated in 24 of them. Either flash or pattern stimulation was used, depending upon the age and visual status of the child. All but one of the children who had normal flash VEPs while cortically blind, recovered normal visual function. All patients with abnormal VEPs had permanent visual impairment or blindness and all but one of those with absent VEPs remained blind. The recovery period was highly variable, ranging from 5 days to 3 years. Thus, flash VEPs recorded during the period of blindness were useful in predicting visual outcome, regardless of etiology. Repeat studies using pattern VEPs were valuable in monitoring recovery in many of these patients.

Blindness↗