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Medical and Mathematical Background
Published in Arwa Ahmed Gasm Elseid, Alnazier Osman Mohammed Hamza, Computer-Aided Glaucoma Diagnosis System, 2020
Arwa Ahmed Gasm Elseid, Alnazier Osman Mohammed Hamza
The number of people with bilateral blindness is shown for the total and the individual glaucoma types. The glaucomatous bilateral blindness is estimated to be 8.4 million (with 4.5 million and 3.9 million people affected by OAG and ACG, respectively). The epidemiology of glaucoma is expected to rise significantly in 2020 to 79.6 million people among the 11.2 million blind people. OAG contributes to 5.9 million cases of vision loss (from 58.6 million) and the ACG share is increased to 5.3 cases of vision loss (from 21 million). The glaucoma distribution numbers are based on the work by Quigley (1999). The various entities of glaucoma have common characteristics that are used to identify the presence of the disease. These include defects in the visual field, excavation of the optic disc, and optic nerve degeneration. IOP is a highly relevant feature of glaucoma. However, 50% of people diagnosed with OAG do not have ocular hypertension (Sommer et al., 1991; Deepikaa et al., 2016).
Sensory System Alterations Following Occupational Exposure to Chemicals
Published in Lucio G. Costa, Luigi Manzo, Occupatinal Neurotoxicology, 2020
Alterations in visual function following carbon disulfide exposure were first observed during ophthalmological examinations.40,41 These old clinical reports described the severe loss of central vision (central scotoma), depressed sensitivity in the peripheral visual field (rod scotoma) and accompanying optic atrophy. In addition, blurred vision, impaired color vision and pupillary changes were reported.41-43 Moreover, electrophysiological analysis revealed that the light/dark ratio of the electrooculogram (EOG) was decreased and that the amplitude of the dark-adapted (rod or scotopic) and light-adapted (cone or photopic) electroretino-grams (ERGs) were decreased with only a slight decrease in latency.39,43-45 Long-term alterations in both the EOG and ERG were still observable in a four-year follow-up study.39 Moreover, high frequency hearing loss has been found in workers chronically exposed to carbon disulfide.46
Advanced Biotechnology
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
The World Health Organization estimates that, globally, 36 million people live with total vision loss and an additional 217 million people suffer from moderate to severe vision impairment (WHO.int). Retinitis pigmentosa (RP) is the leading cause of inherited blindness with 1.75 million patients worldwide (NEI.NIH. gov). It is characterized by progressive disintegration of the photoreceptors within the retina, starting with loss of peripheral vision and poor night vision. Severe cases of RP may progress to tunnel vision and even total blindness. Another vision disorder that compromises the retina is age-related macular degeneration (AMD), which is the leading cause of visual loss among adults over 65 years of age. The disease starts with blurry vision near the center of the visual field, the macula. Patients may develop blank spots that can severely interfere with daily activities. Because of population aging, AMD is projected to more than double from 2.07 million patients in 2010 to 5.44 million by 2050 in the US alone (NEI.NIH.gov).
Out with the old, in with the new: how changes in cricket helmet regulations affect the vision of batters
Published in Journal of Sports Sciences, 2019
Luke Wilkins, David Mann, Stephen Dain, Thomas Hayward, Peter Allen
Visual field testing was performed monocularly on both eyes of each participant using a Humphrey Visual Field Analyser (VFA) with a suprathreshold 76-point 30 degree (60 degree total field) visual-field pattern (Zeiss, Oberkochen, Germany). The VFA measures the visual field using a hemisphere-shaped bowl onto which light stimuli are presented on its inner surface. Participants sat in a darkened room and placed their head on a chinrest within the hemisphere. Throughout the test participants maintained fixation on a central fixation point. Quality of fixation was assessed throughout the test (Heijl Krakau technique) alongside false negative and false positive responses to check for reliability. Stimuli were presented at different positions within the participant’s peripheral vision throughout the 60-degree visual field (Figure 1). Every light stimulus seen was confirmed with the press of a response button.