blinking) was not affected, indicating that different neural mechanisms control each type of eye closure. Interestingly, the patient's ability to voluntarily close both eyelids (i.e. The current paper describes a rare case of a patient who suffered from unilateral apraxia of eye closure as a result of a bilateral stroke. Improved diagnostic and therapeutic methodologies await continuing progress in understanding glare. We provide one pathway through the forest of glare nomenclature and mechanisms. Advances in understanding glare have been hampered by its complex, multidisciplinary nature and limited interdisciplinary communication. Glare is problematic for patients and clinicians despite a century of scientific research. Filters that decrease daytime discomfort or dazzling glare also reduce nighttime mesopic and scotopic sensitivity. Optical glare countermeasures are available for daytime driving but not oncoming automobile headlights at night. Photostress is caused by excessive local retinal photopigment bleaching uncommon in ordinary situations. Neurophysiological research is clarifying how discomfort and dazzling glare depend on different retinal photoreceptors and nociceptive brain pathways involving the trigeminal ganglion and thalamus. Dazzling glare occurs when high illuminances are spread across the retina. Discomfort glare is caused by situational illumination too intense or variable. Colored spectacle or intraocular lens filters reduce both proportionately, so they do not increase retinal image contrast or decrease disability glare. In common environments, glare and target illumination sources have the same or similar spectra. Straylight casts a veiling luminance on the retina, reducing image contrast and impairing vision. To provide a multidisciplinary synthesis of scientific information on disability, discomfort, dazzling, and scotomatic (photostress) glare.Īnalysis and integration of relevant historical and contemporary publications on glare in ophthalmology, illumination engineering, neurology, and other relevant disciplines.ĭisability glare is caused by scattered intraocular light (straylight) not useful for vision.
These observations are interpreted in terms of the known physiology of blink mechanisms. Furthermore this monocular/binocular difference arises only if the stimulus duration is longer than approximately 1 s. The data reveal a clear difference between monocular and binocular stimulation, with the binocular response being much larger than the monocular response. In this paper we report an investigation of the apparent binocular summation of the dazzle reflex using this technique. The dazzle reflex can be measured in human subjects by recording the electrical activity from surface electrodes located near the muscles around the eye. This binocular summation of the dazzle response has not previously been reported.
It is known anecdotally that exposure to a bright light when dark adapted induces an instinctive closure of one eye to reduce the pain associated with dazzle. This response, called the dazzle reflex, is controlled from sub-cortical structures of the brain. Under dark adapted or dim conditions the mammalian visual system is carefully programmed to respond rapidly to the sudden onset of bright lights.
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