malinda
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how do u test it and what will u see?
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| star1
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A Marcus Gunn pupil is said to occur when there is a unilateral lesion in the afferent visual pathway anterior to the chiasm.
The integrity of the afferent pathway may be ascertained by rapidly stimulating each eye in succession with a torch and observing the direct and consensual light response in each. The normal light response is pupillary constriction. In a Marcus Gunn pupil, there is reduced afferent input and the pupils fail to constrict fully. Stimulation of the normal eye produces full constriction in both pupils. Immediate subsequent stimulus of the affected eye produces an apparent dilation in both pupils since the stimulus carried through that optic nerve is weaker.
In severe optic nerve lesions, the eye is amaurotic but a a consensual light response can still be demonstrated.
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| malinda
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thanx star
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| Harry Potter
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Marcus Gunn pupil is a sign of relative afferent pupillary defect where you do see constriction to light stimulus in the affected eye but not as good as a constriction to consensual stimuli. If you have total afferent defect (optic nerve transection), there is no direct reaction and hence no confusion and no need for swinging flash.
HP
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| drbin
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Hi everybody
but what is adie pupil? i think it is like pupil constrict in response to light but not sustained. keeps constricting and dilating. where is it seen?
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| Harry Potter
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Adie's pupil is a dilated pupil that reacts poorly to light but better to accommodation.(similar to argyll robertson in a way) The residual reaction of the pupil is sluggish and "tonic", in the sense if fails to dilate immediately. Adie pupil is usually unilateral and is most often seen in woman. It is commonly associated with a loss of knee jerks. Extra-ocular movements are normal and there is no ptosis.
Localization is to the third nerve cilliary ganglion and is usually due to a virus or other inflammatory processes. The relatively spared response of the pupil to accommodation reflects the much higher percentage of fibers from the ciliary ganglion that innervate the iris for accommodation than for constriction to light. The "tonic" nature of the pupillary reaction reflects denervation hypersensitivity. Adie's pupils, but not normal pupils, will constrict to dilute solutions of pilocarpine.
Care should be taken to not confuse Adie's Pupil with an Argyll-Robertson Pupil, in which the pupil is small and irregular. In Horner's syndrome the affected pupil is small, due to sympathetic denervation of the pupil, but reacts to light.
HP
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| drbin
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thanks HP
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