Pupillary Reaction
Pupillary reaction, also referred to as the pupillary light reflex, is a reflex that controls the diameter of the pupil of the eye. It is measured by the intensity of light that falls upon it. The resulting diameter assists in a person’s adaptation to environmental lightness and darkness. Relatively bright light causes the pupil to constrict (become smaller), whereas a relatively low level of light causes the pupil to expand (become larger). A part of the optic nerve, the photosensitive ganglion cells, senses incoming light. In turn, the oculomotor muscle of the eye causes the constriction of the pupil.
Normal pupil size in adults varies between two to four millimeters in diameter in bright light and from four to eight millimeters in the dark. The precise size of the pupil is controlled by the activity of two muscles: the circumferential sphincter muscle found in the iris, and the iris dilator muscle. The right and the left pupils are generally identical in size.
Evaluation of pupil size and its light reflex mechanism is universally important for both the acute and post-acute phase of care of brain-injured individuals. The Brain Trauma Foundation and The American Association of Neurological Surgeons recommend that individuals with brain trauma be evaluated for asymmetry in pupil size and reactivity to light. Pupillary evaluation is an integral part of the client admission process and to the client’s ongoing care at NeuLife. Medical literature clearly documents that changes in the pupillary light reflex and the size of the pupil are both closely correlated with client outcomes.
Both pupils constrict when exposed to bright light; a phenomenon known as “direct response.” Both also constrict when one pupil is exposed to bright light, a phenomenon known as “consensual response.” Both pupils also constrict when the eye is focused on a close object. This is a phenomenon called “accommodative response.” A pupil is considered to be abnormal if it does not dilate in the dark or if it does not constrict when it is exposed to light or by accommodation.
Accommodation is another way of testing pupillary response. Normally, the pupils constrict while fixating on an object being moved from far away to near the eyes and back again. The failure to constrict under those circumstances may be indicative of lesions on a part of the optic nerve, problems with the pupillary constrictor muscle or lesions on the pathways from the optic tracts to the visual cortex.
Different tests of pupillary reaction are used depending upon the measurement sought and the working diagnosis for the individual. For example, if there is a decreased direct response caused by decreased visual function in one eye, the individual is often thought to have an “afferent pupillary defect.” Verification of this is may be obtained by the “swinging flashlight test.” This involves a flashlight being moved back and forth between the eyes every two to three seconds. An afferent pupillary defect is demonstrated when the flashlight is moved from the normal to the affected eye and the affected pupil dilates in response to light. A normal eye would constrict in response in the light.
NeuLife’s team includes neurologists, RNs and other professionals skilled and expert in furnishing post-acute care to those with vision loss resulting from traumatic brain injuries and other neurological causes.
NeuLife’s philosophy is that healing, wellness and personal fulfillment are best accomplished in a positive and uplifting therapeutic environment where caring staff encourage, assist and support each client so that he or she may achieve specific goals. NeuLife believes personal fulfillment is equally as important as goals to increase function and independence. NeuLife seeks to achieve, for all of its clients, maximized, sustained outcomes that exceed the expectations of all persons served.
NeuLife, in Mount Dora, Florida, is a fully accessible specialized residential post-acute program providing specialized rehabilitation to individuals diagnosed with traumatic brain injury (TBI), spinal cord injury (SCI), traumatic amputations and other catastrophic injuries.
2725 Robie Avenue
Mount Dora, Florida 32757
Call: 800.626.3836
Email: [email protected]
Visit: NeuLifeRehab.com
