Solar energy for village development.

The National Academy of Sciences held a joint workshop with the Government of Tanzania last August on the potential of solar energy for the villages of that country. Costs of five solar technologies (mini-hydroelectric generators, wind, methane generation from organic wastes, photovoltaic cells, and flat-plate solar collectors) were compared with costs of diesel-generated electricity and with electricity from the national grid. Each of the five technologies is either now competitive with diesel or will be in a few years. Although the figures presented are not conclusive since they are derived from calculations rather than an actual test, the results are encouraging enough to warrant serious testing in Third World villages.

Visual involvement in Friedreich's ataxia and hereditary spastic ataxia. A clinical and visual evoked response study.

Visual involvement was assessed in 21 patients with Friedreich's ataxia and in 17 patients with spastic ataxia by neuro-ophthalmic examination and by recording visual evoked responses (VERs). Two thirds of the patients with Friedreich's ataxia had some degree of visual impairment and an abnormal VER, whereas only three of the 17 patients with spastic ataxia showed abnormalities. The patients with Friedreich's ataxia could be subdivided into two groups, one with and the other without visual involvement; there was no correlation between the presence and severity of visual involvement and age or duration of symptoms in the group as a whole. Patients with the most severe degrees of visual impairment usually had flat VERs, whereas in less severely affected cases, the responses were reduced in amplitude, were delayed, and showed an increased degree of temporal dispersion. The findings have pathophysiological implications and raise the question of heterogeneity in Friedreich's ataxia.

The objective assessment of contrast sensitivity function by electrophysiological means.

In recent years it has been shown that it is of considerable clinical value to determine the visual contrast sensitivity function of the patient. This can reveal the wider effects of pathology on the visual system where visual acuity may or may not be affected. There is a comprehensive literature on subjective approaches of obtaining this function in the clinical environment but very little on alternative objective methods. This paper describes the latter approach, which exploits electrophysiological techniques using the visual evoked cortical potential (VECP) to checkerboard onset-offset stimulation. Its application in a variety of disorders of the visual system is described. The importance of selecting the most appropriate stimulus parameters is discussed, and the relative advantages and disadvantages as compared with psychophysical methods are appraised.

Pattern visual evoked potentials in hyperthyroidism.

Pattern reversal visual evoked potentials (VEPs) have been elicited in 16 female hyperthyroid patients before and after treatment and compared with those from a similar group of age and sex matched control subjects. No effect on latency was seen, and although larger amplitude values were noted in the thyrotoxic group these too were not significant. We would conclude that hyperthyroidism per se has little effect on the pattern reversal VEP, and any observed effect on these potentials is probably due to other factors.

Complicated migraine resulting in blindness due to bilateral retinal infarction.

Retinal migraine is not uncommon, but permanent sequelae in the anterior visual pathway are rare. We describe the case of a young woman in whom blindness developed over a six-year period due to recurrent episodes of migraine-related occlusions of a branch retinal artery.

Prognostic significance of the pattern visual evoked potential in ocular hypertension.

This paper reports a prospective study on 49 ocular hypertensive patients to evaluate the prognostic significance of transient abnormalities in the pattern visual evoked potential (VEP) in the development of glaucoma. Seven of 24 patients with VEP abnormalities at diagnosis of ocular hypertension developed glaucomatous field defects in the follow-up period as compared with none of 25 patients with normal VEPs at diagnosis. We conclude that appropriately designed pattern VEP testing is a valuable complement to careful (preferably computerised, static) perimetry. In addition, our findings support the contention that, in glaucomatous disease of the optic nerve, rudimentary pattern processing mechanisms--that is 'Y'-type units of the magnocellular pathways--may be affected earlier than luminance processing mechanisms.

Globe luxation in histiocytosis X.

A boy with histiocytosis X, first diagnosed at the age of 9 months, presented at the age of 5 years with left globe luxation. Under general anaesthesia the globe was reduced and a temporary paracentral tarsorrhaphy carried out. He was started on a course of oral steroids. Two years later he had normal visual acuity, full ocular movements, and healthy fundi.

Leber's optic neuropathy: clinical and visual evoked response studies in asymptomatic and symptomatic members of a 4-generation family.

A clinical and neuro-ophthalmological examination using tests of visual acuity, quantitative visual field analysis, tests of colour discrimination, ophthalmoscopy, and pattern visual evoked responses was performed on 2 symptomatic and 16 asymptomatic members of a family with Leber's optic neuropathy. The visual evoked responses were abnormal in the 2 clinically affected males and in 1 asymptomatic male. Tests of colour discrimination with Ishihara plates, the Farnsworth-Munsell 100 hue test, and the Nagel anomaloscope revealed abnormalities in 8 asymptomatic family members, with the Farnsworth-Munsell test proving to be the most sensitive to mild abnormalities of colour discrimination. The occurrence of detectable neuro-ophthalmological abnormalities within this family is in keeping with the expected pattern of transmission of Leber's optic neuropathy. The significance of detection of presymptomatically affected cases and asymptomatic carriers is discussed.

Visual evoked potential latency and contrast sensitivity in patients with posterior chamber intraocular lens implants.

An electrophysiological investigation of visual evoked potential (VEP) latency and contrast sensitivity was performed in a group of 13 patients who had undergone extracapsular cataract surgery with posterior chamber lens implantation. In spite of good postoperative visual acuity, abnormalities were detected in nine of the group (69%). This study suggests that, even with successfully implanted lenses, there may be a reduction in visual function which could be the result of altered transmission through the plastic lenticulus or fibrosis of the posterior lens capsule, and/or subtle changes in retinal architecture, not observed ophthalmoscopically.

The visual evoked potential in acute primary angle closure glaucoma.

Visual evoked potentials (VEPs) were elicited from 29 patients who had experienced a previous attack of acute primary angle closure glaucoma. The VEPs were shown to be abnormal in at least one of the measures (latency, amplitude, contrast threshold, or slope) in 72.4% of affected eyes, whereas only 41.4% indicated obvious optic nerve damage. It is notable that 48.1% of fellow eyes with no (known) history of acute pressure rise also showed some form of VEP abnormality. The possible pathophysiological mechanisms operating in both affected and fellow eyes are discussed. It is concluded that, despite the presence of possible artefactual influences, the results probably reflect the presence of primary angle closure glaucoma.

Retinal hamartoma in childhood.

Characteristic clinic details of two children affected with pigment-containing tumefactions of the posterior pole are described. The lesion although provisionally regarded as hamartomatous can, as in these two patients, exhibit inflammatory signs which may suggest a reactive inflammatory pathogenesis. Most tests are non-contributory, but fluorescence angiography and electro-oculography are of value in differential diagnosis. The former investigation has indicated that the pattern and intensity of vascular leakage in the mass may change over a period of a year.

LABVIEW graphical user interface for precision multichannel alignment of Raman lidar at Jet Propulsion Laboratory, Table Mountain Facility.

The Jet Propulsion Laboratory operates lidar systems at Table Mountain Facility (TMF), California (34.4 degrees N, 117.7 degrees W) and Mauna Loa Observatory, Hawaii (19.5 degrees N, 155.6 degrees W) under the framework of the Network for the Detection of Atmospheric Composition Change. To complement these systems a new Raman lidar has been developed at TMF with particular attention given to optimizing water vapor profile measurements up to the tropopause and lower stratosphere. The lidar has been designed for accuracies of 5% up to 12 km in the free troposphere and a detection capability of <5 ppmv. One important feature of the lidar is a precision alignment system using range resolved data from eight Licel transient recorders, allowing fully configurable alignment via a LABVIEW/C++ graphical user interface (GUI). This allows the lidar to be aligned on any channel while simultaneously displaying signals from other channels at configurable altitude/bin combinations. The general lidar instrumental setup and the details of the alignment control system, data acquisition, and GUI alignment software are described. Preliminary validation results using radiosonde and lidar intercomparisons are briefly presented.

Electrophysiologically determined contrast sensitivity in patients with ocular hypertension and chronic glaucoma.

Subjectively assessed contrast sensitivity has been found to be abnormal in many patients with glaucoma. We previously reported the use of onset-offset visual evoked potential measurements to determine contrast threshold objectively. We now studied 216 patients (79 with ocular hypertension and 137 with chronic simple glaucoma) with this technique. In comparison with an age-matched control group (68 subjects), mean contrast threshold was found to be significantly different in both patient groups, the degree of significance being greater in the patients with chronic simple glaucoma. Additionally, the slope of the CI-CII amplitude versus log contrast plot was shown to be depressed in the majority of affected eyes in patients with unilateral chronic simple glaucoma. This measure appears to give an indication of suprathreshold contrast processing and is related to the difference in luminance between pattern elements, rather than the quality of the border or "edge" between them. The data support not only an increase in contrast threshold (reduced sensitivity) in early glaucoma and some patients with ocular hypertension but also a suppression in suprathreshold function that is not readily measurable with standard psychophysical methods. The findings are consistent with recent theories concerning the effect of early chronic simple glaucoma on the function of Y-type units of the M (magnocellular)-type pathways.

Visual evoked potential changes in chronic glaucoma and ocular hypertension.

Visual Evoked Potentials have been recorded in a group of normal patients and the results compared with a group of age matched patients with either unilateral chronic glaucoma or ocular hypertension. Pattern reversal transient and steady state responses were analysed and contrast threshold estimated using an onset-offset stimulus. Electrophysiological abnormalities were detected in 82.1 per cent of the glaucoma group and 50.9 per cent of the ocular hypertensives.

Inter- and intra-examiner reliability of the upper cervical X-ray marking system.

This paper investigates the reliability of the upper cervical X-ray marking procedure. The measurement chosen to be examined was atlas laterality. Twenty X-rays were marked by three experienced upper cervical practitioners for the inter-examiner reliability testing, and two of the doctors marked 10 of the films twice for intra-examiner testing. The average measurement for the 60 markings was 1.83 degrees. The average difference between the 3 doctors was 1.05 degrees. The range of error is 57 percent of the average measurement. With interval agreements, it is shown that at the point where all 3 doctors agree 80 percent of the time, the range of error is 2 degrees, this being over 100 percent of the average measurement. The range of error percentages for the 2 intra-examiner tests were 41 percent and 71 percent. It is concluded that with ranges of error of this magnitude any measured differences produced using this system will be just as likely to be from marking error as from actual atlas position change. This should be considered by practitioners who consider these measurements to be objective evidence for demonstrating the results of chiropractic adjustments.

Visual evoked cortical potential to paracentral retinal stimulation in chronic glaucoma, ocular hypertension, and an age-matched group of normals.

Visual evoked cortical potentials (VECPs) to midperipheral stimulation of the visual field were elicited in age-matched groups of patients with unilateral chronic simple glaucoma or ocular hypertension and normal subjects. With a multimodal stimulus approach comprising transient and steady-state pattern reversal and transient onset-offset VECPs, 82.1% of the glaucoma group and 50.9% of the ocular hypertensives revealed significant abnormalities (p less than 0.01) in one or more of the electrophysiological features measured, i.e., latency, phase, amplitude, and contrast threshold.

A citizens' coalition in mental health advocacy: the Maryland experience.

In July 1983 four statewide Maryland citizens' organizations formed a coalition to advocate for persons with mental illnesses. The groups were the Alliance for the Mentally Ill of Maryland; On Our Own of Maryland, a state-wide consumer group; the Maryland Association of Psychosocial Services, representing consumers and providers of rehabilitative services; and the Mental Health Association of Maryland. The chief focus of their advocacy is on making a place in the community for citizens with long-term mental illness. The coalition's rules are simple: to advocate jointly on issues on which they all agree and to not mention their disagreements in public. With a paid lobbyist, the coalition's advocacy has helped produce significant financial and programmatic gains for Maryland's mentally ill citizens.