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Biomedical subjects

J W Walters

Publications and source records attributed to J W Walters.

At least 19 recordsLinked to original sources
PubMed2006

Short wavelength-automated perimetry compared with standard achromatic perimetry in autosomal dominant optic atrophy.

BACKGROUND: Autosomal dominant optic atrophy (ADOA, Kjer-type) is a heterogeneous, non-inflammatory degeneration of retinal ganglion cells. The diagnosis of ADOA can be challenging owing to its insidious onset and large variability in phenotypic expression, both within and between individual pedigrees. The earliest literature reports relatively mild centrocaecal scatomas to white targets in ADOA, but extensive and dense peripheral field loss to coloured targets, especially blue, with Bjerrum perimetry. The phrase "inverted peripheral visual fields to coloured targets" has been used to describe this phenomenon. METHODS: Humphrey standard achromatic perimetry (SAP) and short wavelength-automated perimetry (SWAP) were carried out on five patients with ADOA. RESULTS: Regardless of wide variations in patient age, visual acuity, disc appearance and colour vision, the SWAP mean deviation (MD) was between 10 and 20 times more depressed than the SAP MD. The actual differences ranged from 9.38 to 13.78 dB. CONCLUSIONS: These data are consistent with the original reports suggesting that, early in this disease process, the blue-target deficits are typically peripheral and that this difference between SAP and SWAP perimetry may be a robust indicator of ADOA in both early and late stages of this disease.

Adolescent↗
PubMed2001

The photopic negative response of the flash electroretinogram in primary open angle glaucoma.

PURPOSE: To determine whether the photopic negative response (PhNR) of the electroretinogram (ERG) is reduced in patients with primary open angle glaucoma (POAG). METHODS: ERGs were recorded with DTL electrodes from 62 normal subjects (16 to 82 years), 18 POAG patients (47 to 83 years) and 7 POAG suspects (46 to 73 years) to brief flashes (<6 ms), and also in a few subjects to long (200 ms) red, full-field ganzfeld flashes delivered on a rod-saturating blue background. At the time of ERG measurements, the intraocular pressures of most of the patients were controlled medically. Visual field sensitivities were measured with the Humphrey C24-2 threshold test and optic nerve head cup-to-disc ratio (C/D) was determined by binocular indirect ophthalmoscopy. RESULTS: ERGs of normal subjects contained a slow negative potential following the a- and b-waves, the PhNR, that increased slightly in latency with age. The a- and b-wave amplitudes and implicit times of POAG patients were similar to age-matched controls. In contrast, their PhNRs were small or virtually absent. PhNR amplitudes were reduced even when visual sensitivity losses were small, and were correlated significantly (P < 0.05) with mean deviation (MD), corrected pattern SD (CPSD), and C/D across the population of POAG patients whose MD losses ranged from 1 to 13 dB, CPSDs from 0 to 11 dB and C/Ds from 0.6 to 0.9. PhNRs of most POAG suspects also were small. CONCLUSIONS: PhNR amplitudes in POAG patients are smaller than those of normal subjects. PhNR amplitudes are reduced when visual field sensitivity losses are mild and become even smaller as sensitivity losses increase. There is a potential role for the PhNR in early detection and possibly in monitoring the progression of glaucomatous damage.

Adolescent↗
PubMed2000

Death--whose decision? Euthanasia and the terminally ill.

In Australia and Oregon, USA, legislation to permit statutory sanctioned physician-assisted dying was enacted. However, opponents, many of whom held strong religious views, were successful with repeal in Australia. Similar opposition in Oregon was formidable, but ultimately lost in a 60-40% vote reaffirming physician-assisted dying. This paper examines the human dilemma which arises when technological advances in end-of-life medicine conflict with traditional and religious sanctity-of-life values. Society places high value on personal autonomy, particularly in the United States. We compare the potential for inherent contradictions and arbitrary decisions where patient autonomy is either permitted or forbidden. The broader implications for human experience resulting from new legislation in both Australia and Oregon are discussed. We conclude that allowing autonomy for the terminally ill, within circumscribed options, results in fewer ethical contradictions and greater preservation of dignity.

Attitude of Health Personnel↗
PubMed1993

Psychophysical comparison of four automated perimeters.

It is not unusual for a doctor to detect a field loss on the office perimeter and refer the patient to a setting where a different perimeter is used. In such cases, fields are often repeated because of a lack of "comparability." In this study, we compared the "hill of vision" produced by four major types of perimeters. When possible, we explored alternate user-defined stimulus configurations in order to determine if a rough equivalence could be obtained among the various instruments. Background intensity and target size accounted for many of the differences found in the data. Target color, stimulus duration, and noise had relatively little effect. Despite our stimulus manipulations, subtle (but perhaps significant) differences in the hills of vision remained.

Color Perception↗
PubMed1992

Pigment dispersion syndrome and pigmentary glaucoma.

The pigment dispersion syndrome is a relatively uncommon condition, occurring as a result of pigment loss from the posterior-pigmented epithelium of the iris, with subsequent redeposition of the pigment throughout the anterior chamber. Obstruction of the trabecular meshwork occasionally leads to pigmentary glaucoma, with increased intraocular pressure, optic nerve head changes, and visual field loss. We present two cases of pigmentary dispersion syndrome, one of which progressed to pigmentary glaucoma with the eventual need for laser trabeculoplasty.

Adult↗
PubMed1989

Comparison of oral and intramuscular preanesthetic medication for pediatric inpatient surgery.

The child's fear of injections coupled with the concern that the psychologic advantage of intramuscular premedication may be all or in part negated by the trauma of injections prompted the authors to seek an oral preanesthetic medication to safely and reliably replace injections. The authors describe the results of a prospective, randomized, double-blind study comparing the pharmacologic effects of oral versus injectable preanesthetic medication in 67 healthy pediatric inpatients older than 1 yr. Children given the oral medication (meperidine 3.0 mg/kg, pentobarbital 4.0 mg/kg) were significantly more drowsy in the holding area (P less than 0.001) and more cooperative at the time of induction of anesthesia (P less than 0.01) than the children given intramuscular medication (morphine 0.1 mg/kg, pentobarbital 4.0 mg/kg). There were no other differences between the two groups. These data demonstrate that oral preanesthetic medication can be as or more effective compared with intramuscular medication in producing the desired effects without adverse side effects. As a result of this study, the benefits of preanesthetic medication can now be achieved in nearly all surgical patients without injections.

Administration, Oral↗
PubMed1988

Approaches to ethical decision making in the neonatal intensive care unit.

Despite the "Baby Doe" regulations, there is no consensus on principles for deciding the fate of severely handicapped neonates. This essay analyzes four alternate positions--value of life, parental authority, best interests, and personhood--and suggests for consideration a fifth, ie, proximate personhood. The latter position, building on the strengths of the first four, argues that a handicapped newborn must possess a reasonable potential for minimal personal capacities to have a unique claim to life. Projected minimal capacities include personal self-awareness and net physiological benefit. If newborns are not expected to develop such capacities, parents should be free to choose the option of nontreatment.

Abnormalities, Multiple↗
PubMed1984

High fidelity extended duration electroretinograms.

Virtually all the major advances in vertebrate electroretinogram (ERG) analysis have been made with the use of animal models. Use of human subjects has been avoided largely because of the deleterious effects of many of the techniques used. In the present study, ERG's were recorded from two awake human subjects using direct coupled amplifiers. Pulse duration, wavelength, intensity, and adaptation state were systematically varied in order to produce the classical vertebrate ERG. By altering these stimulus parameters some seldom seen, previously unpublished, human ERG configurations were produced. These data provide a bridge between the human ERG and those previously obtained from other vertebrate preparations.

Adult↗
PubMed1981

ERG off-effects produced by short duration stimuli.

Variable duration square wave pulses of 633-nm light were used to produce electroretinograms (ERG's) in a human subject. When the stimuli were presented on a white light background, the records obtained for stimulus durations greater than 70 msec showed a clearly separated off-response while those of shorter durations did not. By subtracting a common "on-effect" from the ERG's produced by short duration stimuli, the previously unseen off-effect was isolated from records produced by stimulus pulses as short as 5 msec. It appears that the marked increase in b-wave amplitude associated with these short duration stimuli can be attributed to an interaction between "on" and "off" components of the ERG.

Computers↗
PubMed1979

The NIH-ERG ganzfeld stimulator.

The design specifications of a NIH-ERG ganzfield stimulator is discussed. Based on a proposed standard for clinical electroretinography, the stimulator uses stroboscopic stimuli as a whole field flash. But by varying the parameters of wavelengths and background illumination, a complete isolation of the rods and cone systems of the retina is obtained. This information is invaluable at times in early detection and diagnosis of retinal dysfunctions.

Diagnosis, Differential↗
PubMed1977

An examination of Ball's desaturation of intermittent monochromatic light in two patients with retinitis pigmentosa.

In 1971, Walters hypothesized that Bartley's brightness enhancement, the Broca-Sülzer phenomenon, and the desaturation of intermittent trains of short-wavelength monochromatic light (the Ball effect) were all the result of scotopic involvement at photopic levels. In support of this hypothesis, ERG data were presented showing the presence of a scotopic B-wave under conditions which normally did not produce them. In the present paper, data are presente from two patients with retinitis pigmentosa that seem to contradict Walters' hypothesis and to suggest the possibility of a more complex mechanism.

Adult↗
PubMed1977

Visual evoked responses in strabismic and anisometropic amblyopia: effects of check size and retinal locus.

Sinusoidally modulated checker board patterns were used to investigate the effects of check size and retinal location on the "steady-state" visual evoked response (VER) of strabismic and anisometropic amblyopes. Fourier analysis of the averaged VER suggests that the waveforms produced by these techniques are complex, and that they consist of a fundamental component plus 1 or more harmonics. In all of the subjects, the VERs elicited from the amblyopic eyes by small checks in a 3.5-deg disc were significantly smaller in amplitude than those from the nonamblyopic eyes, whereas the responses to larger checks were far more similar. Large annular targets were quite effective in eliciting VERs from the peripheries of both amblyopic and nonamblyopic eyes, and these responses were at times as large as, or larger than, those produced by the central targets. Statistically no significant differences were found between the responses of the amblyopic and the nonamblyopic eyes to the annular targets.

Adolescent↗