Biomedical subjects

J M Wild

Publications and source records attributed to J M Wild.

At least 91 records · Page 5Linked to original sources

PubMed1994

Fatigue effects during a single session of automated static threshold perimetry.

PURPOSE: To determine using a routine clinical program the time course of the fatigue effect in both eyes at a given examination, the influence of rest periods during the examination, and the differences in the fatigue effect between persons with ocular hypertension and age-matched normal subjects. METHODS: Perimetry was undertaken for both eyes of 20 normal persons and 20 persons with ocular hypertension using Program G1X (Interzeag AG, Schlieren, Switzerland) of the Octopus 1-2-3 perimeter. Global mean defect and loss variance were calculated for each of the eight individual stages and global SF was calculated for stages 5 to 8. The superoinferior and nasotemporal hemifield indices and those for within and beyond 17 degrees eccentricity were calculated separately to investigate the locus of the fatigue effect. RESULTS: Group mean mean defect and loss variance deteriorated over stages (P < 0.001) and between eyes for both groups (P < 0.001; P < 0.004). The deterioration in the mean defect was more marked peripherally (P < 0.001) and inferiorly with age and group (P < 0.001) whereas the localized loss was more pronounced peripherally (P < 0.001), superiorly (P < 0.010) and nasally (P < 0.001). A 1-minute break during the examination of a given eye and a 3-minute break between eyes was insufficient to overcome the fatigue effect. The performance of the two groups was almost indistinguishable. CONCLUSIONS: The deterioration in the visual field indices mean defect and loss variance challenges the currently accepted ideal length of a perimetric examination with the conventional algorithms. Confidence limits for the definition of abnormality with these algorithms should reflect the presence of the fatigue effect and be different for the second eye.

Aged↗

PubMed1993

Descending projections of the songbird nucleus robustus archistriatalis.

The descending, efferent projections of nucleus robustus archistriatalis were investigated in male zebra finches and greenfinches with injections of either biotinylated dextran amine or cholera toxin B-chain conjugated to horseradish peroxidase. The results show that in addition to the well-known projections to the tracheosyringeal motor nucleus and the dorsomedial nucleus of the intercollicular complex, there are other projections of comparable density to the ipsilateral nucleus ambiguus and nucleus retroambigualis. Within nucleus ambiguus, robustus axons terminate in close proximity to laryngeal motoneurons which were retrogradely labelled in the same bird by injections of cholera B-chain into the laryngeal muscles; and within nucleus retroambigualis robustus axons terminate in relation to bulbospinal neurons previously shown to project to regions of spinal cord containing motoneurons innervating abdominal expiratory muscles (J.M. Wild, Brain Res. 606:119-124, 1993). These projections of nucleus robustus thus seem well placed to coordinate syringeal, laryngeal, and expiratory muscle activity during vocalization. Other relatively sparse, but distinct, projections of nucleus robustus were found to nucleus dorsolateralis anterior thalami, pars medialis, to a narrow region between the superior olivary nucleus and the spinal lemniscus, and to the rostral ventrolateral medulla. Neurons in these last two locations were retrogradely labelled bilaterally following injections of cholera B-chain into nucleus retroambigualis of one side. Together with sparse contralateral projections of nucleus robustus to all brainstem targets receiving ipsilateral projections, potential pathways are thus identified by which the respiratory-vocal activity controlled by one side of the lower medulla can be influenced by the nucleus robustus of either side, thereby possibly bringing about bilateral coordination of respiratory-vocal output.

Animals↗

PubMed1993

Connections of the auditory forebrain in the pigeon (Columba livia).

Ascending auditory efferents in birds terminate mainly within Field L2, a cytoarchitectonically distinct region of the caudomedial telencephalon. The organization of Field L2, and that of its flanking regions, L1 and L3, was investigated with 14C-2-deoxyglucose (14C-2-DG), cytochrome oxidase, and both retrograde and anterograde tracing techniques. Field L2 was found to contain a high concentration of cytochrome oxidase. Following auditory stimulation, 14C-2-DG autoradiography revealed that Field L2 consists of two adjacent but seemingly discontinuous zones, designated Field L2a, which lies ventromedially, and Field L2b, which lies dorsolaterally. Termination of thalamic efferents: The thalamic auditory nuclei ovoidalis (Ov) and semilunaris parovoidalis (SPO) project predominantly upon Field L2, and possibly sparsely upon L1, L3 and the overlying hyperstriatum ventrale (HV). Ov subnuclei project upon L2a and SPO projects predominantly upon L2b. The topography of the projections is inverted along the ventromedial-to-dorsolateral axis of L2, and is in accord with an inverted tonotopic representation of frequencies; high frequencies (< 3.5 kHz) being found in the more ventromedial parts of L2a, and low frequencies and broad band responses in L2b. Intra- and extratelencephalic connections: Field L2a also receives a substantial projection from HV, but the efferent projections of L2a appear confined to adjacent "neostriatal" regions. The subsequent projections of L2b were not identified in this study. L1 and L3 project predominantly to the dorsal neostriatum (Nd) caudolateral to Field L, and have fewer projections to the caudomedial paleostriatum and anterior hyperstriatum accessorium. Nd projects massively upon the ventromedial nucleus of the intermediate archistriatum (Aivm), which has bilateral projections upon the caudomedial telencephalon and is the origin of a major descending pathway having dense terminations surrounding the ovoidalis complex (Ov and SPO), MLd, the lateral lemniscal nuclei, and sparse terminations within SPO itself. It is suggested that within the telencephalon the major components of the auditory pathway consist of cell groups which collectively correspond to the populations of neurons found within the auditory cortex of mammals.

Afferent Pathways↗

PubMed1993

The avian nucleus retroambigualis: a nucleus for breathing, singing and calling.

Nucleus retroambigualis in songbirds and pigeon was found to contain expiratory-related neurons having spinal projections with terminations in close proximity to abdominal expiratory motoneurons. It was also shown to receive projections from the dorsomedial nucleus (DM) of the intercollicular complex and, in songbirds, from the nucleus robustus archistriatalis (nRbA) of the telencephalon. Nucleus retroambigualis is thus an important nexus in the final common pathway for respiration and vocalization.

Afferent Pathways↗

PubMed1993

The influence of stimulus parameters on the visual field indices by automated projection perimetry.

The various stimulus parameters offered by two standard automated projection perimeters [Humphrey Field Analyser 630 (HFA) and Octopus 201], namely, stimulus size and location and the interaction of adaptation level and stimulus duration, were compared in a sample of 20 patients attending a glaucoma clinic using the visual field indices mean defect (MD), loss variance (LV), short-term fluctuation (SF) and corrected loss variance (CLV). LV and SF were greater with Octopus program 32 compared with Octopus program G1 (P < 0.02). No difference in the indices was found between stimulus sizes I and III for HFA program 30-2. MD was greater for program 30-2 compared with program 32 (P < 0.002) when expressed in terms of log (L/delta L) whereas LV (P < 0.02) and SF (P < 0.02) were greater for program 32. All differences were considered to be negligible in the clinical sense.

Adaptation, Ocular↗

PubMed1993

Evaluation of FASTPAC: a new strategy for threshold estimation with the Humphrey Field Analyser.

A new strategy for threshold estimation, FASTPAC, has been introduced for the Humphrey Field Analyser with the aim of improving the efficiency of visual field examination without loss of accuracy. FASTPAC was compared to the standard 4-2 double staircase strategy in 98 normal volunteers (age 23-83 years). One eye of each subject was examined with both strategies on two visits using Program 30-2. The order of strategy was randomised. FASTPAC examination time was 43% faster than the standard algorithm, but the mean sensitivities were similar. Short-term fluctuation was 24% higher with FASTPAC (P < 0.001). Most parameters were adversely affected by increasing age. FASTPAC offers a valid alternative to the standard strategy in the examination of suspected normal fields and should always be considered as an alternative to the threshold-related screening strategies. The performance of the algorithm in the identification of field loss and in areas of reduced sensitivity awaits further study.

Adult↗

PubMed1993

Evaluation of FASTPAC, a new strategy for threshold estimation with the Humphrey Field Analyzer, in a glaucomatous population.

PURPOSE: A new fast strategy for the estimation of threshold, FASTPAC, has been introduced for the Humphrey Field Analyzer. The aim of this study is to evaluate the performance, in a glaucomatous population, of FASTPAC compared with the standard full-threshold 4-2-decibel (dB) double-staircase strategy. METHODS: The sample consisted of 30 glaucoma patients experienced in automated perimetry, ranging in age from 26 to 84 years. One eye of each patient was examined with both strategies using program 24-2, target size III. The order of strategy was randomized for each patient. The results were analyzed using analysis of covariance for a two-period crossover trial. Mean deviation, pattern standard deviation, short-term fluctuation, corrected pattern standard deviation, number of stimulus presentations, and examination time were analyzed separately; test sequence and severity of field loss were considered as between subject factors and age as a covariate. RESULTS: The FASTPAC algorithm demonstrated a 36% saving in examination time (P < 0.001), a lower mean deviation (0.91 dB) (P < 0.001), and a greater short-term fluctuation (0.64 dB) (P = 0.008). The differences in mean deviation (P = 0.015) and short-term fluctuation (P = 0.033) became greater with an increase in age. As the severity of the field loss increased, the short-term fluctuation increased (P = 0.043), and examination time was increased for the FASTPAC strategy, while it became shorter for the standard full-threshold strategy (P = 0.033). CONCLUSIONS: The FASTPAC strategy reduced the examination time but exhibited a decreased estimate of field severity and a greater intra-test variance.

Adult↗

PubMed1993

Effect of filters on disability glare.

Disability glare is the reduction in visual performance caused by a peripheral glare source. We examined the effect of a long wavelength pass (red) and a short wavelength pass (blue) filter on disability glare in the presence of varying amounts of induced wavelength dependent stray light. Measurements were made in the absence of any filter and then repeated in the presence of the red and blue filters whose luminous transmission factors were equal relative to both the stimulus and the glare source. Neither of the filters had any effect on disability glare. Filters not only reduce the amount of veiling luminance from the glare source, but also reduce the ability to detect the stimulus. Disability glare was not significantly different with the red and blue filters, even in the presence of wavelength dependent scatter. Calculation of the veiling luminance transmitted by each filter revealed that the difference in veiling luminance in the two filter conditions was insufficient to result in a measurable difference in disability glare.

Adult↗

PubMed1993

Maximizing the dynamic range of the humphrey field analyzer for blue-on-yellow perimetry.

The conditions employed for blue-on-yellow perimetry (i.e. a blue stimulus filter and a high luminance yellow background) are in conflict with those that allow a maximum dynamic range. A modification is described for increasing the dynamic range of the Humphrey Field Analyzer (HFA) for blue-on-yellow perimetry. The position of the HFA stimulus bulb was lowered by reducing the length of both terminals. A concave mirror with a 28 mm radius of curvature was positioned behind the lowered stimulus bulb to give a filament image partly above and partly overlapping the original filament profile within the confines of the size V stimulus patch diameter. The modification achieved a 60% increase in the light output on the default 0 dB value of 10,000 apostilbs and, therefore, a useable dynamic range for blue-on-yellow perimetry of 2.94 log units. The effective increase in voltage supply to the stimulus bulb permitted a filament life of 260 operating hours. Furthermore, the modification ensured the correct calibration of the instrument.

Color↗

PubMed1993

Magnification perimetry.

PURPOSE: The authors used a method of spatial scaling to quantify the eccentricity-related decline in differential light sensitivity as a function of visual field meridian and age. METHODS: Differential light threshold at the fovea was measured in two groups of subjects of differing age (young mean age, 23.6 yr; standard deviation, 2.4 yr; elderly mean age, 69.6 yr; standard deviation, 6.2 yr) using a Goldmann size I stimulus moving across fixation at 1 degree/sec. With luminance kept constant, eccentricity thresholds for kinetic stimuli of increasing magnification were then measured. The results were analyzed in terms of the E2 value, which specifies the eccentricity at which the stimulus size must double to maintain performance equivalent to that at the fovea. RESULTS: For the young subjects, eccentricity thresholds increased linearly with an increase in stimulus diameter for most meridians. E2 varied between 5-12 degrees, depending on the meridian, and showed the same meridional trend as that of retinal ganglion cell distribution, although the magnitudes of E2 were different. For the elderly subjects, the eccentricity thresholds increased in a nonlinear manner with the stimulus diameter. CONCLUSIONS: Further factors, such as spatial summation, must also determine the eccentricity dependence of the differential light threshold because ganglion cell density decreases at a much faster rate than the differential light threshold. The most marked effects of age on differential light sensitivity occur at the fovea and beyond 20 degrees in the peripheral field, with a relative sparing in the pericentral area.

Adult↗

PubMed1993

Pointwise topographical and longitudinal modeling of the visual field in glaucoma.

PURPOSE: To develop a suitable mathematical model for the description of the pointwise distribution of sensitivity across the visual field in glaucoma. METHODS: The pointwise distribution of sensitivity at any given stimulus location for any given examination was described by a joint topographical and longitudinal model. The topographical element modeled the pointwise distribution of sensitivity using a second-order polynomial function in terms of the respective stimulus coordinates whereas the longitudinal element modeled the pointwise distribution of sensitivity using multiple linear regression in terms of the sensitivity at the given location determined at one or more previous examinations. The sample comprised Humphrey Field Analyser (Humphrey Instruments, San Leandro, CA) Program 30-2 and 24-2 fields from 49 patients attending a glaucoma clinic for an average of 3 years. RESULTS: The constant term of the polynomial correlated highly with the mean deviation and moderately with the pattern standard deviation. The goodness-of-fit between the modeled and the measured field increased as an exponential function of the number of previous examinations. The median R2 was 19.6% for the first examination and 83.6% for the sixth examination. The group median optimum percentage of error between the measured and modeled sensitivity at each test location was below 10% (i.e., less than 3 dB), increased with increase in eccentricity, was greater at the extremities of the superior field and varied as a function of the severity of the field loss. CONCLUSION: The model seems to be a promising way to evaluate visual field progression.

Glaucoma↗

PubMed1993

The visual field indices in primary open-angle glaucoma.

PURPOSE: The distribution of sensitivity across the visual field, as determined by automated threshold static perimetry, can be summarized in terms of visual field indices. Such indices can be weighted for the variation in threshold at each eccentricity. The aims of this study were to determine the influence of the weighting factor, the relationship between the unweighted indices derived from Programs 30-2 and 24-2, and the relationship between the number of double determinations of threshold and the magnitude of the short-term fluctuation. METHODS: One visual field derived by Program 30-2 of the Humphrey Field Analyzer was selected from each of 60 consecutive patients with primary open-angle glaucoma. The first two fields from each individual patient were avoided. Unweighted visual field indices were calculated and compared with the Program 30-2 weighted indices using an assessment of agreement evaluated with respect to the 95% confidence limits of the population. RESULTS: The weighting function had no influence on the mean deviation, but it caused a slight reduction in the short-term fluctuation and an elevation in the pattern and corrected pattern standard deviations. There was little difference between the indices generated by Programs 30-2 and 24-2. The short-term fluctuation increased with an increase in the number of double determinations of threshold. CONCLUSIONS: The weighting function had little clinical influence on the visual field indices. The indices derived from Programs 30-2 and 24-2 were similar, and the short-term fluctuation would better reflect the intratest variability if all available double determinations of threshold were used to calculate the index.

Aged↗

PubMed1992

Direct and indirect "cortico"-rubral and rubro-cerebellar cortical projections in the pigeon.

In birds the red nucleus is the most rostral cell group in the brain having projections to all levels of the spinal cord (Cabot et al., Prog. Brain Res., 57:79-108, 1982), but its sources of afferents are incompletely known. In order to determine these, a series retrograde and anterograde tracing experiments was carried out, largely with cholera toxin B-chain conjugated to horseradish peroxidase. The results show that a sparse and diffuse projection to the red nucleus arises from deep regions of the hyperstriatum accessorium (HA) of the anterior Wulst, and that a much more dense projection arises from the caudal part of the nucleus principalis precommissuralis and the medial part of the medial spiriform nucleus (SpMm). These last two sources were themselves shown to receive a substantial projection from HA of the anterior Wulst. The red nucleus was also shown to project upon the cerebellar cortex of lobule VI, and SpM upon the cerebellar cortex of lobules VI through IX (Karten and Finger, Brain Res., 102:335-338, 1976; Clarke, J. Comp. Neurol., 174:535-552, 1977). Double retrograde labelling experiments with fluorescein and rhodamine labelled latex microspheres injected into the cerebellar cortex and spinal cord showed that the rubrocerebellar cortical neurons are a different population from, although intermixed with, the rubrospinal neurons.

Animals↗

PubMed1992

Assessment of physiologic statokinetic dissociation by automated perimetry.

The effects of age, stimulus size, meridian, and eccentricity on physiologic statokinetic dissociation were investigated in clinically normal subjects using the Humphrey field analyzer (HFA, model 640), an automated perimeter capable of both static and kinetic perimetry. The right eyes of 20 age-matched young and 20 age-matched elderly volunteers was examined along the 15 degrees and 195 degrees meridians with six Goldmann size I and five size III kinetic stimuli. These were chosen to produce a spread of discrete eccentricities. Kinetic sensitivity was determined seven times for each stimulus, and the mean stimulus locations were expressed in terms of their x and y coordinates. Static sensitivity for each stimulus size then was determined seven times at each of the corresponding locations using a custom threshold program. The area under each sensitivity gradient was determined using the trapezium rule. Group mean kinetic sensitivity was greater than group mean static sensitivity (P < 0.001), and this difference was largely independent of age, stimulus size, meridian, and eccentricity.

Adult↗

PubMed1991

Time-related variation in normal automated static perimetry.

The effects of phase of eye test and order of eye examined were investigated in 38 normal subjects using a customized 30-point central threshold program of the Humphrey Field Analyzer 640. This program, designed to be completed within 5 minutes, was successively repeated three times for each eye (i.e., three phases for each eye) at two visits separated by an interval of approximately 2 weeks. Both global and pointwise group mean sensitivity decreased in a time-related manner, deterioration being greater for the second eye at each visit, for both 200 ms and 100 ms stimulus durations.

Adult↗

PubMed1991

Long-term follow-up of baseline learning and fatigue effects in the automated perimetry of glaucoma and ocular hypertensive patients.

The detection of change in the visual field is confounded by factors associated with the patient response. Sixteen patients who had previously undergone a training regime in automated perimetry over a short time period were followed up to evaluate the longer term learning and fatigue effects. The patients, all attending a glaucoma clinic, were originally naive to automated perimetry. The training period had comprised examination of the right followed by that of the left eye with the Humphrey Field Analyser 630 on each of 3 successive days and again after an interval of 12 days. The follow-up study comprised two examinations on 2 successive days after a follow-up period of between 5 and 15 months (mean 8.7 months). The learning effects present over the initial training period were not observed at the follow-up whilst the fatigue effects in the fellow eye were still apparent.

Adult↗

PubMed1991

Central projections of the nodose ganglion and the origin of vagal efferents in the lamb.

Injections of WGA-HRP and CTB-HRP were made into the cervical vagus or the nodose ganglion in a series of lambs, in order to define the sensory projections and motor origins of the vagus nerve. Injections into the nodose ganglion were much more successful than injections into the cervical vagus in effecting the desired result. The former produced labelling of both descending and ascending components of the solitary tract (TS). The descending component terminated massively in all ipsilateral and certain contralateral subnuclei of the nucleus of the solitary tract (nTS) and in the upper cervical spinal cord. Patchy terminations were also observed within the interpolated subnucleus of the nucleus of the spinal trigeminal tract, and within Lamina I of the upper cervical cord. The ascending component of TS terminated in rostral regions of the nTS, and in specific portions of the principal sensory trigeminal nucleus and the lateral parabrachial and Kölliker-Fuse nuclei. The motor origins of the vagus nerve arose almost completely ipsilaterally in the dorsal motor nucleus of the vagus, the nucleus ambiguus, and the caudal portion of the nucleus retroambiguus situated in the lateral part of the intermediate grey at upper cervical spinal levels. Labelled neurons in the nucleus dorsomedialis of the upper spinal cord were thought not to project their axons into the cervical vagus.

Animals↗

PubMed1990

Peripheral and central terminations of hypoglossal afferents innervating lingual tactile mechanoreceptor complexes in Fringillidae.

Injections of cholera toxin B subunit conjugated to horseradish peroxidase (CTB-HRP) were made into the lingual branch of the hypoglossal nerve in four species of finch in order to identify the innervation of the mechanoreceptors of the dermal papillae of the tongue, and simultaneously to determine the pattern of central projections of lingual hypoglossal afferents. The results showed that hypoglossal fibers innervate all the Herbst corpuscles and terminal cell receptors of the elaborately organized papillae of the dorsum of the tongue, of the shorter papillae in the ventral tongue, and the loose collection of Herbst corpuscles in the subpapillary region. Labelled fibers were also observed in the intralingual glands, in the intrinsic tongue muscles, and in the posterodorsal epithelium where they formed budlike structures. Retrogradely labelled cell bodies were located in the jugular ganglion and their central processes ascended and descended throughout the brainstem within the descending trigeminal tract (TTD). Terminal fields were observed within the dorsolateral part of the nucleus caudalis of TTD, predominantly ipsilaterally, and within the medial part of the dorsal horn of the first 4-6 cervical segments bilaterally. There were dense patches of termination over a dorsolateral subnucleus of the interpolated nucleus of TTD, and within two regions of the principal sensory trigeminal nucleus: a large one laterally and a small one medially. Terminal fields were also observed within the nucleus ventralis lateralis anterior of the rostral solitary complex, and within adjacent nuclei, which are probably equivalent to the dorsal sensory nuclei of the facial and glossopharyngeal nerves of other avian species. The results are interpreted in the light of the role of the tongue in species-specific patterns of feeding in finches, and the possible requirement for the central integration of touch and taste.

Afferent Pathways↗