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Threshold static perimetry is generally done using automated equipment. It is used for rapid screening and follow-up of diseases involving deficits such as scotomas, loss of peripheral vision and more subtle vision loss. Perimetry testing is important in the screening, diagnosing, and monitoring of various eye, retinal, optic nerve and brain ...
A negative value indicates field loss, while a positive value indicates that the field is above average. A P value is provided if the global indices are abnormal. It provides a statistical representation of the population. For example, P <2% means that less than 2% of the population have vision loss worse than measured [19]
The visual field is "that portion of space in which objects are visible at the same moment during steady fixation of the gaze in one direction"; [1] in ophthalmology and neurology the emphasis is mostly on the structure inside the visual field and it is then considered “the field of functional capacity obtained and recorded by means of perimetry”.
According to IPS Perimetry Standards 1978 (2002): "Perimetry is the measurement of [an observer's] visual functions ... at topographically defined loci in the visual field. The visual field is that portion of the external environment of the observer [in which when he or she is] steadily fixating ...[he or she] can detect visual stimuli."
In psychophysics, sensory threshold is the weakest stimulus that an organism can sense. Unless otherwise indicated, it is usually defined as the weakest stimulus that can be detected half the time, for example, as indicated by a point on a probability curve. [1] Methods have been developed to measure thresholds in any of the senses.
In neuroscience and psychophysics, an absolute threshold was originally defined as the lowest level of a stimulus – light, sound, touch, etc. – that an organism could detect. Under the influence of signal detection theory , absolute threshold has been redefined as the level at which a stimulus will be detected a specified percentage (often ...
The flicker fusion threshold, also known as critical flicker frequency or flicker fusion rate, is the frequency at which a flickering light appears steady to the average human observer. It is a concept studied in vision science , more specifically in the psychophysics of visual perception .
For many sensory modalities, over a wide range of stimulus magnitudes sufficiently far from the upper and lower limits of perception, the 'JND' is a fixed proportion of the reference sensory level, and so the ratio of the JND/reference is roughly constant (that is the JND is a constant proportion/percentage of the reference level).