pr20
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A 45-year old woman with a long history of progressive myopia develops sudden patchy loss of vision in her right eye.She is very alarmed and rushes to her family doctor.Funduscopic examination reveals a large retinal detachment in the right eye.The retina in the left eye is normal.When the pupillary light reflex is tested by swinging a light from her left eye to her right eye,the physician would likely note which of the following?
A. Constriction of the right pupil and constriction of the left
B. Constriction of the right pupil and dilatation of the left
C. Dilatation of the right pupil and constriction of the left
D. Dilatation of the right pupil and dilatation of the left
E. No reaction of the right pupil and constriction of the left
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| hope4dabest
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A????...in case u have explaination do plz post it..i always mess up here
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| new_n_lost
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C. Dilatation of the right pupil and constriction of the left??
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| SURVIVOR
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D??
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| cricket9014
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?
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| Tiff
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?????? E ??????
Anyone know the correct answer?
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| new_n_lost
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I dont know why people even bother to post the question when they dont even have the courtesy to post the answer or atleast say that they dont have the answer.
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| seem.bh
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this is the same question silver{guru} asked....
true.. agree with nnl 
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| lakshya_0_7
Forum Elite
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should be D...in marcus gunn pupil..when the light is shone on the right eye,retina wouldnt get stimulated coz its damaged..so there would be no pupillary reflex..neither the direct nor the consensual coz afferent is gone....so both the pupils should dialate ....
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| silver
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http://www.prep4usmle.com/forum/thread/67404/ post #13
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| spinal shock
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definitely A coz pupillary constriction is done by oculomotor nerve since the light was directed to the eye with normal afferent pathway. the damaged retina cant do anything about it
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| spinal shock
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new-n-lost that occurs in optic nerve atrophy
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| new_n_lost
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spinal shock wrote:
definitely A coz pupillary constriction is done by oculomotor nerve since the light was directed to the eye with normal afferent pathway. the damaged retina cant do anything about it
CORRECT ANSWER: D
The patient is exhibiting Marcus-Gunn phenomenon.
When light strikes the retina, the pupillary light reflex is automatically triggered, leading to simultaneous constriction of both pupils. In the absence of adequate light entering the eye, for example following retinal detachment or optic neuritis, paradoxical dilatation of the pupils occurs. The retina receives far less light than it normally would, and the pupils dilate in order to absorb as much light as possible.
spinalshock wrote:
new-n-lost that occurs in optic nerve atrophy
Now i m curious please explain me how and what do you mean by that in optic atrophy. Oh i think you meant that Choice C happens to be in Optic Atrophy right ?? Hmm yeah i think i have made a mistake there will be further reading up on it.
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| zursha
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so new n lost,, does that mean, that it doesnt matter which eye has the retinal detachment, both eyes eventually will be dilated because they need to absorb more light even if the left eye, in this case, it is normal???plz let me know,
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| new_n_lost
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zursha wrote:
so new n lost,, does that mean, that it doesnt matter which eye has the retinal detachment, both eyes eventually will be dilated because they need to absorb more light even if the left eye, in this case, it is normal???plz let me know,
In Marcus Gunn pupil the affected pupil doesnt percieve light to be that strong so the constriction is less then normal eye. Therefore when swinging light from normal eye to affected the lesser degree of constriction makes it appear that the pupils are dilated.
In other words the when the light is shone in the normal eye both pupils constrict and when the light is shone on the affected eye both pupils also constrict but to a lesser degree thus make it appear as if they are dilating in comparison. Therefore its called paradoxical dilation of the affected eye.
I hope i have explained well
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FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
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| zursha
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ohhh now i get it, sorry for replying so late, it took me long time to figure out how to get to this specific post, but no u have explained it well, thank you
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