Professionalism had changed.
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Editorial↗
Biomedical subjects
T Buckingham
Publications and source records attributed to T Buckingham.
Movement detection threshold and ocular hypertension.
PURPOSE: To determine whether patients with ocular hypertension (OH) have elevated oscillatory movement displacement thresholds (OMDT) indicative of early neural damage. METHODS: Evidence of early neural loss was sought using OMDT. The OMDT of 29 normotensive individuals were compared with those obtained from 44 untreated age-matched OH eyes (20 male, 24 female). RESULTS: A mean OMDT at 15 sec arc at 40 years of age was obtained in normotensive individuals, the age trend increasing by about 4 sec arc per decade. About one-third of all ocular hypertensives (13 cases; 6 male, 7 female), who were dismissed without treatment, exhibited abnormal OMDT. An equal proportion of abnormal thresholds were observed in individuals in each decade, although the age trend diverges from that established for normotensives with increasing age. Mean OMDT for ocular hypertensives (37.1 sec arc) were significantly different (t = 2.7, p < 0.007) from the mean obtained from normotensives (22.2 sec arc). CONCLUSION: The results emphasise the need for more rigorous differentiation of OH using psychophysical techniques indicating early neural damage.
Adult↗
Shared care postoperative management of cataract patients.
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Cataract Extraction↗
[Intravenous withdrawal of infected cardiac pacemaker electrodes. Apropos of 5 cases].
Infection of a cardiac pacemaker and its electrodes is one of the most serious complications after implantation of a pacemaker, as it can be life-threatening and constitutes an absolute indication for complete withdrawal of the implanted material which, up until recently, could only be performed by thoracotomy or sternotomy with or without cardiopulmonary bypass. A new transvenous technique for complete removal of the infected pacemaker system has been recently described. We report 5 cases of infected pacemaker systems in which this technique was used successfully allowing withdrawal of 10 electrodes and thereby avoiding the need for a major surgical operation.
Aged↗
Optimal temporal frequencies in oscillatory movement hyperacuity measurements of visual function in cataract patients.
Hyperacuity tasks have been suggested for the assessment of potential visual function in the presence of cataracts. To test this suggestion, hyperacuity thresholds for an oscillating bar were measured in 30 subjects with idiopathic cataract and in 24 age-matched normals over a range of oscillation frequencies. Each subject's cataract was categorized using the Oxford Clinical Cataract Classification and Grading System. Cataract was found to have a significant effect on thresholds, although a differential morphological effect on thresholds was equivocal. Thresholds at higher temporal frequencies were significantly raised when compared to the normal group. The main conclusion to be drawn from this study is that motion hyperacuity thresholds appear unaffected by cataract at low oscillation frequencies and should be used in preference to higher frequencies in the assessment of such patients.
Aged↗
Magnetic orotracheal intubation: a new technique.
We sought to determine the effectiveness of a magnet placed over the thyroid cartilage in the neck to guide an endotracheal tube into the trachea. Forty patients aged 18 to 60 yr with normal airway anatomy (ASA grade I) who required general anesthesia with an endotracheal tube and paralysis for their surgery were chosen and informed consents were obtained. The tip of the epiglottis was exposed with a No. 3 MacIntosh laryngoscope, and a magnet was held over the thyroid cartilage. A catheter with stylet was placed behind the epiglottis allowing the magnet to pull the stylet and catheter close to the glottic opening. The catheter was advanced into the trachea over the stylet and its position was confirmed by auscultating the lungs and by capnography. An extension tube was connected to the catheter, and the endotracheal tube was guided into the trachea over the catheter. The tracheas of 37 patients were intubated on the first attempt with the magnet. The tracheas of the remaining three patients could not be intubated on the first attempt but were successfully intubated without complications on the second attempt. An additional five patients with an anterior larynx whose tracheas could not be intubated with direct laryngoscopy also had tracheal intubation with a magnet. This magnet-guided technique can be used when it is difficult to expose a patient's larynx. It is noninvasive, simple, and can be used without any delay when expensive flexible fiberoptic endoscopes are not readily available. The procedure takes an average of 1 to 2 min.
Adult↗
Visual dysfunction in type II diabetic patients revealed by a hyperacuity test.
Displacement thresholds for an oscillating bar, which fall into the hyperacuity range, were determined in 21 subjects with non-insulin dependent diabetes mellitus and 19 age-matched visually normal controls. The diabetic subjects were classed as either having minimal or no retinopathy. Whilst thresholds for the diabetic group were significantly raised above those of the normal group, there were no significant differences in thresholds between the diabetic subgroup with retinopathy and the subgroup without. Greater thresholds tended to be found at higher frequencies of oscillation as the known duration of the diabetes increased.
Diabetes Mellitus, Type 2↗
The influence of stimulus luminance and contrast on hyperacuity thresholds for oscillatory movement.
Hyperacuity thresholds for oscillatory movement were determined under conditions of decreased contrast and decreased luminance. Responses were found to be resistant to contrast reduction down to 15%; below this level thresholds increased. The contrast response function is thus similar to that of the magnocellular channel of the visual system. Systematic reduction in luminance caused a corresponding rise in thresholds. It is suggested that this effect is due to undersampling of the retinal image as a result of a lowered quantal absorption and an increase in critical duration of temporal integration at lower levels of luminance.
Contrast Sensitivity↗
The effect of spatial parameters on oscillatory movement displacement thresholds.
Earlier work has established that oscillatory movement displacement thresholds (OMDT) are a form of hyperacuity. There is speculation that the mechanism determining OMDT, like motion perception in general, involves direct motion sensing at high temporal frequencies of oscillation and spatial localization processes (from which motion is inferred) at low temporal frequencies, which are both hyperacuities in their own right. OMDT were determined, for three experienced observers, over the temporal frequency range 1-15 Hz, for three stimulus lengths and three stimulus widths. Both decreasing stimulus length and decreasing stimulus width increased OMDT at all temporal frequencies. Furthermore, the resulting functions consistently exhibit a "kink" in the temporal frequency midrange. The results are interpreted as evidence that there are two subsystems involved in the analysis of visual motion with the kink indicating the transition where one system begins to predominate over the other.
Humans↗
Hyperacuity thresholds for oscillatory movement are abnormal in strabismic and anisometropic amblyopes.
The hyperacuity performance of amblyopic individuals is known to be abnormal, particularly on vernier tasks. Oscillatory movement displacement thresholds (OMDT's) a form of hyperacuity, were investigated over a range of temporal frequencies (1, 4, 7, 10, and 13 Hz) in 8 normal controls, 5 strabismic amblyopes, and 4 anisometropic amblyopes to see if this form of hyperacuity was also affected by amblyopia. OMDT's were found to be significantly raised in all of the strabismic amblyopes and three of the four anisometropes over all temporal frequencies investigated when compared to the control group. In the fourth anisometrope, OMDT's were raised at low temporal frequencies only. The findings are interpreted as evidence that magnocellular and parvocellular channels are affected in the amblyopic visual system. The functional loss in amblyopia cannot be described completely unless both temporal and spatial thresholds are investigated.
Adult↗
Influence of clinical characteristics and shock occurrence on ICD patient outcome: a multicenter report. The Bilitch Registry Group.
Data on 1,281 patients from the Bilitch implantable cardioverter defibrillator (ICD) registry were reviewed to evaluate ICD patient characteristics and survival, and the impact of ICD shock occurrence on outcome. The mean ejection fraction was 34.3%; 78% had coronary disease, 471 patients had at least one shock thought to be appropriate, and 231 patients died. Causes of death included: arrhythmic (41%), nonarrhythmic cardiac (37%), and noncardiac (22%). Cumulative survival from all-cause mortality at 1, 3, and 5 years was 89%, 76%, and 64%; survival from all-cause cardiac death was 93%, 90%, and 76%; survival from arrhythmic death was 96%, 92%, and 87%. Patients who had received a shock had a trend towards a worse long-term prognosis. Shock patients also had a small increase in the prevalence of coronary disease and a somewhat lower ejection fraction than the remainder of the population.
Cause of Death↗
Ventricular arrhythmia due to intracoronary papaverine: analysis of QT intervals and coronary vasodilatory reserve.
Intracoronary papaverine commonly produces striking QT interval prolongation with rare but serious ventricular dysrhythmias reported. Because of 3 cases of severe papaverine-induced dysrhythmia in our laboratory, QT intervals and hemodynamic and intracoronary velocity data collected during intracoronary papaverine administration were retrospectively reviewed in 34 patients; 20 patients with angiographically normal coronary arteries (group 1) and 14 patients (group 2) before and (group 2) after single-vessel left coronary angioplasty. QT intervals increased from 394 +/- 44 to 464 +/- 73 msec, 414 +/- 47 to 504 +/- 95 msec, and 410 +/- 41 to 486 +/- 75 msec for groups 1 and 2 before and after angioplasty, respectively (all P less than 0.01). There was no correlation with hemodynamic, electrocardiographic, or coronary vasodilatory reserve responses and change in QTc interval. In the 3 index patients having significant papaverine-related arrhythmias, a baseline QT interval was prolonged (after prior papaverine exposure) in only 1 in association with torsade de pointes. These data indicate that QT interval prolongation after papaverine is a common occurrence, but that the production of ventricular dysrhythmia is probably idiosynchratic in origin. In view of these findings, we recommend that appropriate antiarrhythmic preparations be in place for patients receiving intracoronary papaverine.
Adult↗
A monoclonal antibody to a zona pellucida-proteinase inhibitor binding component on murine spermatozoa.
A monoclonal antibody, J-23, was produced to an epitope of a binding (acceptor) component on the plasma membrane in the acrosomal cap region of the mouse sperm head. The component binds a proteinase inhibitor of seminal vesicle origin at ejaculation and participates in the in vitro binding of capacitated sperm to the zona pellucida. The antibody, an IgM molecule, recognizes affinity purified acceptor, crude acceptor and whole sperm as determined by ELISA methodology. The antibody reacts with a 15,000 molecular weight component, the size previously determined for the acceptor, found in the supernatants of frozen-thawed cauda epididymal sperm. In addition, it binds to a 21,000 molecular weight component generated by mixing an excess of purified inhibitor (6400 daltons) with a crude acceptor preparation. J-23 binds to an epitope in the same region of the sperm head as does the inhibitor. This epitope becomes fully expressed during epididymal maturation and is found only in the lumen of epididymal tissues. Pretreating sperm with J-23 inhibits their ability to bind the inhibitor as well as the zona pellucida. Pretreating sperm with the inhibitor has little effect on the binding of J-23. These data indicate that J-23 recognizes an epitope on the acceptor but the epitope is not directly involved with inhibitor binding.
Animals↗
Oscillatory movement displacement thresholds: resistance to optical image degradation.
Vernier acuity, under optimal conditions, appears remarkably resistant to image degradation. This characteristic has been used to assess neural function in cataract patients who exhibit poor spatial resolution. Conventional resolution tests fail to differentiate between neural and optical causes of visual loss. The oscillatory movement displacement threshold--the smallest amplitude of oscillation which gives rise to the perception of movement--provides an alternative hyperacuity test. This may offer advantages over vernier acuity. The effect of image defocus upon displacement thresholds for a sinusoidal contrast grating of spatial frequency 2 c deg-1 was investigated for high (15 Hz) and low (2 Hz) oscillation frequencies. With visible stationary references, subjects were more sensitive to oscillation frequencies of 2 Hz than to 15 Hz (F 1,9 = 33.34, p less than 0.005) whilst blur of up to 2 dioptres had no significant effect (F3,27 = 1.73, p greater than 0.1). Simulating media opacities by spatial degradation affected both grating acuity and contrast sensitivity functions, whilst displacement thresholds remained largely unaffected. Results suggest that oscillatory movement displacement thresholds may be of value in assessing ocular neural dysfunction in the presence of media opacities.
Cataract↗
Movement in decline? Oscillatory movement displacement thresholds increase with ageing.
Displacement thresholds for continuous oscillatory movement were determined for ten subjects in each of three age groups--20-23, 40-55 and 60-80 years. Oscillation frequencies of 1, 2, 3, 5, 8, 13 and 20 Hz were used, all subjects having a corrected visual acuity of 6/5. A randomized block factorial design of analysis of variance revealed significant effects of both temporal frequency of oscillation (F6,189 = 4.10, p less than 0.001) and age (F2,189 = 46.98, p much less than 0.001). The deterioration in movement sensitivity occurs equally at both high and low temporal frequencies--no significant interaction effects being revealed (F12,189 = 0.45, p = not significant). The frequency effects are ascribed to underlying mechanisms mediating movement perception. Reasons for decreased movement sensitivity with increasing age are discussed.
Adult↗
Theory and evidence for a clinical hyperacuity test.
An accurate assessment of the integrity of the visual system behind opaque ocular media is of vital clinical significance, especially with regard to surgical intervention. Several techniques which are currently available to assist in this task are considered with regard to their value. Theoretical considerations indicate that hyperacuities, by virtue of their resistance to optical image degradation, should constitute ideal candidates to perform the above evaluation. Hyperacuity studies involving cataract simulation support this view, as does the clinical data which is presently available. Further work should reveal an optimum hyperacuity configuration or a battery of hyperacuity tests and establish their clinical merit.
Humans↗
The influence of temporal frequency and wavelength on beta movement.
The maximum displacement threshold for beta (apparent) movement was determined using small near-monochromatic stimuli subtending 2 min arc, over the frequency range 1.67-6.67 Hz. Displacement thresholds for the apparently oscillating spot were dependent upon both temporal frequency (F(9,903) = 1413) and wavelength (F(12,903) = 19.6), the stimuli having been equated for luminance. Significant interaction effects (F(108,903) = 3.32) demonstrated that the influence of colour varied with temporal frequency. It is suggested that short-range apparent movement over this frequency range may be mediated by a mechanism which is colour dependent.
Adult↗
The rise and fall of intra-ocular pressure: the influence of physiological factors.
A number of physiological factors can influence the intra-ocular pressure of patients with normal, healthy eyes leading to the misinterpretation of tonometric findings. The influence and duration of four commonly encountered factors--drinking water, coffee, alcohol, and exercise--were investigated employing a non-contact tonometer. Drinking 1 litre of water increased the IOP for up to 140 min with a mean maximum increase of 4.4 mmHg. A similar change was induced by coffee, the increase lasting up to 95 min and displaying a mean maximum increase of 4.0 mmHg. The intra-ocular pressure fell with alcohol consumption by a maximum of 3.7 mmHg, regaining pre-test values in all subjects after 65 min. Vigorous exercise produced an immediate fall in mean intra-ocular pressure of 4.3 mmHg, initial pressure being restored in all subjects after 65 min. The impact of such factors upon normal physiology are discussed together with the implications for routine tonometry.
Adolescent↗