This response requires intact ipsilateral facial nerve function as well as an intact ipsilateral cerebellum. The cortico-bulbar pathways to the facial nerve nucleus (CN VII) then transmit the motor information. The information generated in the contralateral visual (occipital) cortex is forwarded to the motor cortex to initiate a motor response. The afferent part of this response involves the same structures as the visual pathways. Abnormal function is manifested by a reduced to absent blink or globe retraction. Normal function is demonstrated by a blink or retraction of the globe in response to the threat or even an aversive head movement. ![]() This is a learned response, not a reflex, to a perceived threat. The entire peripheral and central visual pathway must be intact for a response to occur. In the stoic patient it may be necessary to tap the eyelids being tested so that the animal is aware of the test. Care must be taken not to create too much air turbulence. With a cooperative patient the medial and lateral aspects of each eyeball (retina) can be tested. The free hand moves rapidly toward the open eye stopping prior to causing physical contact. The animal's head is held still and the contralateral eye is covered with a hand. It is present from about six to twelve weeks of age depending on the species and the breed. Clinical Overview–This is a cortically mediated eyelid closure produced by a threatening or unexpected gesture or action suddenly appearing in the near visual field. ![]() As such it is not a reflex and involves integration of the visual pathways with cortical perception of a threat and a motor response in the form of a blink. This test evaluates a behavioral response to a visual threat.
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