CONTENTS | SEARCH | ABOUT THE BOOK

Pupillary Responses (CN II, III)

Printer Friendly

First, record the pupil size and shape at rest. Next, note the direct response, meaning constriction of the illuminated pupil, as well as the consensual response, meaning constriction of the opposite pupil.

29. Pupil Light Reflex

[Snapshot from video]

Click the image above to view the video. (QuickTime Required)

In an afferent pupillary defect there is a decreased direct response caused by decreased visual function in one eye. This can be demonstrated with the swinging flashlight test, in which the light is moved back and forth between the eyes every two to three seconds. The afferent pupillary defect becomes obvious when the flashlight is moved from the normal to the affected eye, and the affected pupil dilates in response to light. Under normal conditions, the pupil constricts in response to light. Brief oscillations of pupillary size called hippus occur normally in response to light which should not be confused with an afferent pupillary defect.

30. Swinging Flashlight

[Snapshot from video]

Click the image above to view the video. (QuickTime Required)

Finally, test the pupillary response to accommodation. Normally, the pupils constrict while fixating on an object being moved from far away to near the eyes.

31. Accomodation

[Snapshot from video]

Click the image above to view the video. (QuickTime Required)

What is Being Tested?

Direct response (pupil illuminated). The direct response is impaired in lesions of the ipsilateral optic nerve, the pretectal area, the ipsilateral parasympathetics traveling in CN III, or the pupillary constrictor muscle of the iris.

Consensual response (contralateral pupil illuminated). The consensual response is impaired in lesions of the contralateral optic nerve, the pretectal area, the ipsilateral parasympathetics traveling in CN III, or the pupillary constrictor muscle.

Accommodation (response to looking at something moving toward the eye). Accommodation is impaired in lesions of the ipsilateral optic nerve, the ipsilateral parasympathetics traveling in CN III, or the pupillary constrictor muscle, or in bilateral lesions of the pathways from the optic tracts to the visual cortex. Accommodation is spared in lesions of the pretectal area.

See Neuroanatomy through Clinical Cases Chapter 13 for further details on the neuroanatomy of pupillary reflexes and pupillary abnormalities.

Open Site Navigation Menus Previous page Next pageNext or previous page