Conjugate gaze

·   Conjugate gaze refers to the eyes working in unison. A disorder of conjugate gaze means that patients are unable to look in certain directions with both eyes, such as upward, downward or laterally.

o Centre for lateral conjugate gaze is seen in frontal lobe cortices & in occipital lobe cortices

o Frontal lobe centers for lateral conjugate gaze lie in the posterior aspect of frontal lobes.

o They are quite close to the motor cortex and hence conjugate deviation of the eyes is seen in many paralytic strokes.

o Frontal lobe center for lateral conjugate gaze control voluntary conjugate eye movements to the opposite side. Teleologically, this makes sense: the left half of the brain "sees" space on the right side, therefore the left side of the brain controls movements of the right arm and leg, as well as eye movements to the right side.

o On one side of frontal lobe center destruction, as in a cerebral infarct, the tonic impulses from the opposite frontal lobe cause a deviation of the eyes towards the side of the lesion and patient looks to­wards the lesion and away from the paralyzed side.

·   Conjugate deviation occurs only in the acute phase of an infarct and eventually, the patient will recover, but there may be an intermediate stage where they are unable to move the eyes away from the lesion on command, yet able to follow an object to the opposite side.

·  Occipital lobe center for lateral gaze control the ability of the eyes to follow an object to the opposite side.

· In a patient with destruction of the right frontal center but with an intact right occipital lobe center cannot look to the left on com­mand but may be able to follow an object to the left.

· If the patient is unable to follow a moving object, such as a finger, you can assess the occipital lobe center by having them fixate on an immobile object while you move their head.

·  Remember! Lesions of the occipital center for lateral conjugate gaze are less common than lesions of frontal center for lateral conjugate gaze.

·   Brainstem center for lateral conjugate gaze is in the pons, very close to the sixth nerve nuclei.

·   The right frontal center connects with the left pontine center and the left frontal center with the right pontine center. The left pontine center controls lateral conjugate eye movement to the left, and the right pontine center controls lateral conjugate eye movement to the right.

·   Thus, a patient who has a destruction of one pontine center will look away from the lesion and towards the paralyzed side because of the unopposed action of the opposite pontine center. Recovery of conjugate gaze after a brainstem lesion is unusual.