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  #1  
Old 07-27-2011
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Star pupillary reflex question

A 58 year old woman comes with progressive myopia and sudden patchy loss of vision. Fundoscopy shows retinal detachment in right eye and normal left eye. What is the finding u observe when u do a swinging light source from left eye to right eye?

A. Constriction in right and constriction in left eye.
B. Constriction in right eye and dilatation in left eye.
C. Dilatation in right eye and constriction in left eye
D. Dilatation in right eye and dilatation in left eye.
E. No reaction in right eye and constriction in left eye.
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  #2  
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I think ans is A
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Old 07-27-2011
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i think it's D
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Old 07-27-2011
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I think its A.
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I think its A. Left will still have constriction and due to the consensual reflex maintained so should the right.
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Ans D Dilation of both eyes, rt sided afferent pupillary defect
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Old 07-28-2011
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Quote:
Originally Posted by mle2resident View Post
A 58 year old woman comes with progressive myopia and sudden patchy loss of vision. Fundoscopy shows retinal detachment in right eye and normal left eye. What is the finding u observe when u do a swinging light source from left eye to right eye?

A. Constriction in right and constriction in left eye.
B. Constriction in right eye and dilatation in left eye.
C. Dilatation in right eye and constriction in left eye
D. Dilatation in right eye and dilatation in left eye.
E. No reaction in right eye and constriction in left eye.
Marcus Gunn pupil the ans is D the response upon showing the light from normal to the affected pupil will produce dilatation of both eyes due to defective afferent pathway its imp to note tht this pupil does has some response due to light though very slow
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Old 07-28-2011
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Originally Posted by qurat21 View Post
Marcus Gunn pupil the ans is D the response upon showing the light from normal to the affected pupil will produce dilatation of both eyes due to defective afferent pathway its imp to note tht this pupil does has some response due to light though very slow
if its marcus gun it should b c then i think so ? correct me if am wrong?
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Originally Posted by yasirsattar75 View Post
if its marcus gun it should b c then i think so ? correct me if am wrong?
when the afferent is affected hw cn u ve consensual light reflex???
visualise it with the optic pathway ur afferent is nt working hw cn u send order to the mid brain so no bilateral pupillary response
the method basically is u throw the light in normal eye u c constriction of pupil n immediately throwing it onto affected side u c dilatation of pupil
there is a nice video on you tube i dnt knw hw to post it must c
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In a normal individual if you shine a light into 1 eye you should get constriction of both pupils, and when you take the light away you should see dialation of both pupils. Given the question stating that the right afferent is deffective I would assume that it would be the same as if you just took away the light source all together, thus causing dialation of both pupils. Correct me if im wrong.

Ans D
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Old 07-28-2011
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Question

Quote:
Originally Posted by qurat21 View Post
when the afferent is affected hw cn u ve consensual light reflex???
visualise it with the optic pathway ur afferent is nt working hw cn u send order to the mid brain so no bilateral pupillary response
the method basically is u throw the light in normal eye u c constriction of pupil n immediately throwing it onto affected side u c dilatation of pupil
there is a nice video on you tube i dnt knw hw to post it must c
in this case physician is performing indirect consensual light reflex from normal left to right side ..so left afferents are used and as we know efferents are bilateral so other eye also show response in case of indirect consensual light reflex . but we call marcus gun pupil is a pupil showing no response on indirect light reflex ..righteye dilated and left eye constricted by swinging light from left to right ..i hope so am right ? this was according to kaplan q bank one when i read that
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Quote:
Originally Posted by yasirsattar75 View Post
in this case physician is performing indirect consensual light reflex from normal left to right side ..so left afferents are used and as we know efferents are bilateral so other eye also show response in case of indirect consensual light reflex . but we call marcus gun pupil is a pupil showing no response on indirect light reflex ..righteye dilated and left eye constricted by swinging light from left to right ..i hope so am right ? this was according to kaplan q bank one when i read that
in case of marcus pupil the afferent is affected the efferent is intact here the physician is throwing light first into the left eye the normal one u will c the constriction in both the eys n then u throw lite in right eye u c dilation in both...lets c wts the ans
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Old 07-28-2011
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Arrow D is the right answer

Yes. The answer is D. Dilatation in right and left eye.

This patient is exhibiting Marcus Gunn pupil (relative afferent pupillary defect). Diagnosed by swinging flashlight.

When light strikes the normal retina(left eye in this case), the pupillary reflex is triggered causing constriction of pupils in both eyes.

But in cases of retinal detachment/optic neuritis, the retina receives far less light than normal and hence the pupils dilate to absorb as much light possible. Hence the afferent stimulus is weak, causing dilatation of both pupils.
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Search Relative Afferent Pupillary Defect



(the music is a little bit annoying!)
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