31. Accomodation

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 (see Neuroanatomy Through Clinical Cases 3e, Figure 13.8).

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 (see Neuroanatomy Through Clinical Cases 3e, Figure 13.8).

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. The accommodation (near) response is spared in lesions of the pretectal area that may impair the pupillary light response, a condition called “light-near dissociation.”

See Neuroanatomy Through Clinical Cases 3e, Chapter 13 for further details on the neuroanatomy of pupillary reflexes and pupillary abnormalities (see KCC 13.5).