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The Neurological Pupil index, or NPi, is an algorithm developed by NeurOptics, Inc., that removes subjectivity from the pupillary evaluation. A patient's pupil measurement (including variables such as size, latency, constriction velocity, dilation velocity, etc.) is obtained using a pupillometer, and the measurement is compared against a normative model of pupil reaction to light and ...
Pupillometry, the measurement of pupil size and reactivity, is a key part of the clinical neurological exam for patients with a wide variety of neurological injuries. It is also used in psychology . [ 1 ] [ 2 ]
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When the optic nerve is damaged, the sensory (afferent) stimulus sent to the midbrain is reduced. The pupil, responding less vigorously, dilates from its prior constricted state when the light is moved away from the unaffected eye and towards the affected eye. This response is a relative afferent pupillary defect (or Marcus Gunn pupil). [1]
Many automated pupilometers can also function as a type of pupil response monitor by measuring pupil dilation in response to a visual stimulus.. In ophthalmology, a pupillary response to light is differentiated from a pupillary response to focus (i.e. pupils may constrict on near focus, as with the Argyll Robertson pupil) in the diagnosis of tertiary syphilis.
The pupil of the human eye can range in size from 2 mm to over 8 mm to adapt to the environment. The human eye can detect a luminance from 10 −6 cd/m 2, or one millionth (0.000001) of a candela per square meter to 10 8 cd/m 2 or one hundred million (100,000,000) candelas per square meter.
By analogy with a camera, the pupil is equivalent to aperture, whereas the iris is equivalent to the diaphragm. It may be helpful to consider the Pupillary reflex as an 'Iris' reflex, as the iris sphincter and dilator muscles are what can be seen responding to ambient light. [2] Whereas, the pupil is the passive opening formed by the active iris.
Tonic pupils are fairly common – they are seen in roughly 1 out of every 500 people. A person with anisocoria (one pupil bigger than the other) whose pupil does not react to light (does not constrict when exposed to bright light) most likely has Adie syndrome – idiopathic degeneration of the ciliary ganglion.