PubMed Health⌕ Search

Biomedical subjects

G E Holder

Publications and source records attributed to G E Holder.

16 recordsLinked to original sources
PubMed1995

The assessment of clinical investigations: the Greenwich Grading System and its application to electrodiagnostic testing in ophthalmology.

The aim of the study was to describe the Greenwich Grading System, a simple method developed for assessing the value of a clinical investigation, and to investigate its application to electrodiagnostic testing (EDT) in ophthalmology patients. This was done by means of a retrospective case analysis carried out on 95 unselected, consecutive patients referred from a district ophthalmology department for electrophysiological investigation at a regional neurosciences centre. The classification was developed to quantify the effect of EDT on the diagnosis, investigation and treatment in each case. From this, an overall value of EDT in management could be assessed for different groups of patients. It was found that the classification was easy to apply and analyse. EDT was valuable in 80% of patients referred, and was classified as essential or important in 53 (56%) patients. In no patient did EDT adversely affect the clinical outcome. The diagnosis was changed in 7 (7%) patients, and made in 5 (5%). Diagnostic certainty was increased in a further 62 (65%) patients. Other investigations were avoided by performing electrophysiology in 28 (29%) cases. Treatment was initiated in 6 (6%) cases and altered in 8 (8%). It is concluded that the Greenwich Grading System, as applied to EDT in ophthalmology, demonstrated the value of electrophysiological investigation in ophthalmology patients and identified the patient groups which benefit most from testing.

Electrodiagnosis↗
PubMed1994

Gold foil electrodes: a two-center study of electrode reliability.

Using the routine techniques employed at our two centers for recording pattern electroretinograms and a variety of methods, we investigated the reliability of the gold foil electrode over repeated uses. We found no significant difference between the pattern electroretinograms recorded with new electrodes and those that had had such extensive use in patients that they were believed unsuitable for further clinical use. We therefore continue to recommend the gold foil electrode for repeated use.

Electrodes↗
PubMed1992

The differentiation of peripheral effector neuron failure from acute brain stem dysfunction in a critically ill patient.

A patient appeared to be in coma following pneumococcal meningitis, an intracerebral haemorrhage, and a cardiac arrest. Late in the course of his illness neurophysiological investigations confirmed a proposal that he also had a fulminant acute demyelinating polyneuropathy which, for a period of five days, rendered the patient completely unresponsive. The patient recovered and is now working without any disability.

Adult↗
PubMed1991

The incidence of abnormal pattern electroretinography in optic nerve demyelination.

This report describes the pattern electroretinogram (PERG) findings in 141 patients with optic nerve demyelination in one or both eyes. The overall incidence of PERG abnormality in the 199 eyes with abnormally delayed pattern visual evoked potential (PVEP) P100 component was 39.2%, with 84.6% of these PERG abnormalities being confined to the N95 component. The incidence of abnormal PERG was greater (53.3%) in those eyes with a history of retrobulbar neuritis than in those with sub-clinical demyelination (22.8%). The importance of stimulus parameters is noted. The value of the PERG in the improved interpretation of an abnormal PVEP is discussed.

Adolescent↗
PubMed1989

Pattern visual evoked potentials and pattern electroretinograms in hypothyroidism.

This study reports the pattern visual evoked potential (PVEP) findings in 10 patients with idiopathic hypothyroidism. Eight of these patients also had pattern electroretinography (PERG) performed and six were additionally seen after treatment with thyroxine. Only one patient had definitely abnormal PVEPs at the time of initial recording. PERGs at this time were of abnormal latency and subnormal amplitude. Following treatment with thyroxine the patient became euthyroid. Repeat electrodiagnostic testing now showed both PERGs and PVEPs within the normal range, having markedly improved in both latency and amplitude. This suggests that the PVEP delay was probably secondary to reversible central retinal dysfunction.

Electroretinography↗
PubMed1989

Visual evoked potentials in the assessment of patients with non-functioning chromophobe adenomas.

The results of visual evoked potential (VEP) examination in 34 patients with histologically confirmed chromophobe adenoma are described and discussed in relation to the clinical, radiological and surgical findings. The VEP is shown to be a reliable method of assessing the function of the intracranial visual pathways which is often more sensitive than conventional methods of examination.

Adenoma, Chromophobe↗
PubMed1989

Pattern electroretinography in patients with delayed pattern visual evoked potentials due to distal anterior visual pathway dysfunction.

Between March 1983 and January 1988 delayed pattern visual evoked potentials (PVEP) were observed in 67 patients with distal visual pathway dysfunction. Many of these patients had been referred for neurophysiological examination because of possible optic nerve dysfunction. These patients also had pattern electroretinography (PERG) performed which in all cases showed an abnormality of the main positive P50 component. None of these patients had an abnormality confined to the negative N95 component, the type of abnormality usually found if the PERG is abnormal in optic nerve disease. It is suggested that PERG recording should now be a routine adjunct to the PVEP in the assessment of anterior visual pathway dysfunction.

Adolescent↗
PubMed1987

Significance of abnormal pattern electroretinography in anterior visual pathway dysfunction.

The pattern electroretinogram (PERG) findings in 72 patients with disease of the anterior visual pathways are presented in relation to the site of dysfunction. Two components of the PERG are described which are selectively involved in different pathologies. In particular, the main positive P50 component is invariably affected in retinal/macular dysfunction, whereas the late negative N95 component is principally affected in optic nerve disease.

Adolescent↗
PubMed1985

Pattern visual evoked potential in patients with posteriorly situated space-occupying lesions.

The potentials evoked by pattern reversal stimulation (2/sec, 11 degrees field, 26' high contrast checks) are described in 22 patients with intracranial space-occupying lesions lying posterior to the optic chiasm. Seventeen (77%) of these patients had clinically demonstrable visual field defects. The nature and position of the lesion was defined by CT scan, by cerebral angiography, or at operation. Completely normal pattern visual evoked potentials (VEPs) were recorded in four patients (18%), all of whom had full visual fields. Definitely abnormal VEPs occurred in 12 patients (55%), 11 with visual field defects. The remaining six patients (27%), all with visual field defects, had VEPs that were inconsistently abnormal and they are rated as equivocal. The findings are discussed with particular attention to the importance of stimulus and recording parameters.

Adult↗
PubMed1978

The effects of chiasmal compression on the pattern visual evoked potential.

The visual evoked potentials (VEPs) to pattern reversal stimulation (26' individual check subtense, 11 degrees total field) have been examined in 10 patients with proven chiasmal compression. Bipolar occipital-sylvian and occipital-parietal recordings were taken with electrodes placed according to the Modified Maudsley system. In all patients abnormalities, taking the form of latency delays or amplitude reductions, were found in response to monocular stimulation which, without exception, were maximal in the traces corresponding to the hemisphere contralateral to the field defect. In seven patients responses to a 13' pattern were also examined. In six of these the lateralisation of abnormality was enhanced. The discrepancy between these and previous findings is discussed, the importance of stimulus and recording parameters being stressed.

Adult↗
PubMedDate not supplied

Guidelines for basic pattern electroretinography. Recommendations by the International Society for Clinical Electrophysiology of Vision.

The pattern electroretinogram is a retinal response that can be evoked by viewing an alternating grating or checkerboard. It is receiving increasing clinical and research attention because it can provide information about inner retinal cells and the macula. However, clinicians may have trouble choosing between different techniques for recording the Pattern electroretinogram that have been described in the literature. The International Society for Clinical Electrophysiology of Vision has prepared guidelines for a basic pattern electroretinogram recording procedure to aid new users in obtaining reliable responses and to encourage more uniformity among existing users.

Electroretinography↗
PubMedDate not supplied

Check size tuning of the pattern electroretingoram: a reappraisal.

The pattern electroretinogram was recorded to checkerboard stimuli with a wide range of check sizes and two stimulus field sizes. Check sizes ranged from 0.25 degree to 7 degrees (field size, 16 degrees x 14 degrees) and 0.25 degree to 15 degrees (field size, 32 degrees x 27 degrees) in 14 and seven subjects, respectively. Reversal rate was 4.5/s. For minimal intrusion of blink artifacts the interrupted stimulation technique was employed. The P50 and N95 components of the pattern electroretinogram were evaluated separately. With both stimulus field sizes amplitude of P50 and N95 was maximal between 0.75 degree and 1 degree. With smaller check sizes the amplitude dropped monotonically. With larger check sizes field size played a role: with the 16 degrees x 14 degrees field, P50 gradually dropped to 89% from 1 degree to 7 degrees, which was paralleled by N95 only up to 7 degrees, where N95 dropped to 81% (p < 0.05). With the 32 degrees x 27 degrees field, there was no significant difference in size dependency between P50 and N95 for large check, both components staying constant from 1 degree to 15 degrees. We conclude that there is only minor large-check attenuation of the pattern electroretinogram, especially with a large field. The apparent field-size dependency may explain previous discrepancies in the literature.

Electroretinography↗