China
Africa
Explore chapters and articles related to this topic
Epilepsy and Driving
Published in Stanley R. Resor, Henn Kutt, The Medical Treatment of Epilepsy, 2020
A. James Rowan, Daniel Luciano, H. Richard Beresford
The most common form of reflex epilepsy, which is particularly relevant to driving, is photosensitive epilepsy. Photosensitivity may be a characteristic of some primary generalized epilepsies or may be seen in isolation (19,20). Such patients are particularly sensitive to flicker frequencies of 15–18 Hz (20). Gastaut (1) describes a patient who had an absence attack while driving, triggered by the flickering of light through the trees. He points out that she continued driving as part of an ictal automatism. Photosensitivity is usually suppressed by pharmacotherapy (19,20), and such patients may be able to drive after photic activation during EEG has been eliminated.
Early detection of dementia
Published in Stephen Curran, John P. Wattis, Practical Management of Dementia, 2018
Sonja Krüger, Miguel A. Bertoni, Stephen Curran
Critical Flicker Fusion Threshold (CFFT) is a well-established neurophysiological technique that has been extensively studied in young and older healthy volunteers. The neurophysiological basis of flicker perception is well described.34 Flickering light directly influences cortical activity (measured by electroencephalogram, EEG), and although flickering light is able to initiate neuronal activity in various parts of the visual system (from retina to cortex), the temporal resolution of CFFT appears to be determined principally by the occipital cortex. Above a particular frequency, flickering light does not appear to flicker and the point at which this occurs is the CFFT and is a measure of the information-processing capacity of the central nervous system. In the ascending mode, the frequency of flicker is gradually increased until the flickering lights appear to stop flickering – this is the ascending threshold. In the descending mode, the frequency of flicker is gradually decreased until the lights appear to start flickering – this is the descending threshold. The CFFT is the average of the ascending and descending thresholds.
Observed Effects of the Unconscious Mind and the Unknown World. 4: Acoustic and Other Physical Effects
Published in David E. H. Jones, Why Are We Conscious?, 2017
In the 1970s, when the Toronto Society for Psychical Research devised its project to ‘invent’ the ghost ‘Philip’, it encountered the unexpected oddity that Philip could, if asked, make the lights flicker. They illuminated the room partly by a system of lamps of different colours—they had hoped to get a visible apparition and had planned to photograph it if it appeared. To make a light flicker, you might alter the voltage driving it. This sometimes happens because of an irregularity in the voltage maintained by the power company. All the electrical apparatus supplied from that source should then behave strangely. The Toronto group did not suffer in this way; its other electrical apparatus and that in the rest of the building remained steady. To make just one bulb flicker, you would either have to make the insulator around it conducting or you would have to increase the electrical resistance of the wire supplying it. Philip once extinguished a lightbulb completely for a long time. The obvious interpretation was that it had simply failed, say by a break in its filament, but it was later found to be entirely sound. The Toronto group also noticed the strange way in which one psychic character suffered repeated failures of his rented television set. The company owning the set examined it on several occasions and found that the same small resistor had burned out. Maybe it held off a high voltage, and its resistance had briefly fallen.
Acquired Vitelliform-Like Lesion in Uveitis: A case-series
Published in Ocular Immunology and Inflammation, 2022
Arash Maleki, Sydney Look-Why, Soheila Asgari, Ambika Manhapra, Sebastian Gomez, C. Stephen Foster
There were 12 patients and 21 eyes in the AVLL group. Confirmed sarcoidosis, diagnosed though a lung biopsy, was observed in one out of twelve patients. Birdshot chorioretinopathy (3 patients), anterior uveitis (1 patient), intermediate uveitis (2 patients), idiopathic panuveitis (3 patients), syphilitic panuveitis (1 patient), and multifocal choroiditis (1 patient) were the other diagnoses in the remaining patients. Prior to the first visit with us, systemic corticosteroid or immunomodulatory therapies had been employed in six patients. Some of these patients had received both. Visual symptoms included decreased vision in seven patients (58.3%), floaters in four patients (33.3%), photopsia and photophobia each in three patients (25%), redness and pressure pain in two patients (16.7%) and color vision defect in one patient (8.33%). The average of LogMAR vision was 0.51 ± 0.34 (20/60) (range: 0.1–1.2). Active anterior chamber inflammation and vitreous inflammation was present in eight (66.7%) and six (50%) patients, respectively. ICGA had been done in 9 patients and 18 eyes, which showed patches of active choroiditis (44.5%) with no abnormalities in the sub-foveal area. Three patients had done full-field ERG. One patient had an abnormal 30-Hz flicker ERG.
Straylight in fish-eye disease: visual quality and angular dependence of straylight
Published in Expert Review of Ophthalmology, 2022
Didrika Sahira van de Wouw, Bram de Jong, IJE van der Meulen, TJTP van den Berg
Straylight was measured using the compensation comparison method developed by Van den Berg [13,14] as implemented in the C-Quant (Oculus GmbH, Wetzlar, Germany) [15,16]. It measures the effect of light scattering as relevant for vision, i.e. its intensity in the visual field. In short, the instrument presents a flickering annulus with 7 degree radius to the patient. The patient observes two adjacent half fields in the center of the annulus, one containing only straylight-induced flicker, while in the other compensation flicker is added. The patient has to indicate which side flickers strongest for a series of presentations with different levels of compensation flicker. When the two are perceived as equal, the strength of the straylight is known. This straylight value is expressed as the logarithmic value of the straylight parameter s. More straylight corresponds to a higher log(s) value and more disturbed vision. The C-Quant also provides the reliability of the measurement by giving the expected standard deviation (ESD). Only measurements with ESD < 0.1 were used. In general, the C-Quant is a reliable method, but each eye was measured twice nevertheless. The average of the two measurements was taken as a result and the SD was calculated.
Dr Gordon Plant’s Festschrift Tidings
Published in Neuro-Ophthalmology, 2022
Sui H. Wong, Susan Mollan, Simon J Hickman, Stephen Madill, Luke Bennetto, Sarah Cooper
The second half of the session was structured around three excellent presentations. Professor Jette Frederiksen discussed the flicker test for specifically diagnosing demyelinating optic neuropathy. The flicker test involves a patient matching the subjective brightness of a flickering field with a steady state illuminated field. Interestingly, the brightness of a flickering field is overestimated if a patient performs the test with an eye previously affected by demyelinating optic neuritis. Professor Vivek Lal presented ‘Neuro-Ophthalmic Challenges in India’. He discussed the ongoing issue with tuberculous meningitis (manifesting as basal exudates on magnetic resonance imaging [MRI]) and other encephalitides now more unusual in the West, such as subacute sclerosing panencephalitis in the context of previous measles infection. Professor Lal presented his case series of patients with ophthalmic migraine, which are specifically different from the group reclassified as third nerve neuritis. He also discussed methanol induced toxic optic neuropathy and the associated basal ganglia destruction. The session concluded with Dr Roberto Ebner presenting his experiences with corneal neurotisation and using confocal microscopy to visualise corneal reinnervation.