kaplanQ light reflex

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kaplanQ light reflex

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Lim
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09/04/06 - 09:36 AM

A 25-year-old male gets into a brawl outside a bar. During the altercation, someone pulls out a gun and shoots him in the head. The bullet enters the man's temple and severs his right optic nerve completely. He is quickly transported to a nearby emergency room and an emergency physician tests his pupillary response by shining a light in the right eye. What will the physician most likely find?

A. No pupillary constriction in the right eye, and no pupillary constriction in the left eye.
B. No pupillary constriction in the right eye, but pupillary constriction in the left eye.
C. Pupillary constriction followed by pupillary dilation in both eyes
D. Pupillary constriction in the right eye, and no pupillary constriction in the left eye.
E. Pupillary constriction in both eyes.
F. Pupillary dilatation in both eyes.

please,answer and expl...

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Leopard
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09/04/06 - 11:18 AM

Any reflex has three components

Afferent Limb
Center
Efferent limb

Both types of light reflexes i.e Direct and Consensual have one common "afferent Limb " i.e OPTIC NERVE.So when it is cut both are lost .Direct one in the ipsilateral eye and consensual in the opposite eye.So answer is

A

Best of luck

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klimt
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09/04/06 - 02:37 PM

Agree, it's A
If the right optic nerve is damaged 'completely', there is no transmission of the stimulus=light neither for the direct nor for the consensual reflex...

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Lim
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09/04/06 - 04:31 PM

thanks,Leopard and klimt.

what not Marcus Gunn pupil(paradoxical dilation)?
i guess because there's total sever on the right optic nerve?
so in result to be Marcus Gunn pupil there should be a little sparing of light sense like in a case of retinal detachment? can you give me examples of Marcus gunn pupil?

thanks again.

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Leopard
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09/04/06 - 04:45 PM

Optiv neuritis in MS

GL

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docarchana
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09/04/06 - 04:49 PM

marcus gunn in retinal detachment or optic neuritis of one eye.

Lim
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09/04/06 - 05:02 PM

so Marcus gunn pupil is seen in only partial damage of optic nerve(afferent limb)?
thanks,Leopard,docarchana.

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docarchana
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09/04/06 - 05:16 PM

in the initial q, what will happen if light is shone into left eye?

Leopard
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09/04/06 - 05:22 PM

docarchana wrote:
in the initial q, what will happen if light is shone into left eye?

Both reflexes will be present i.e

Direct in Lt eye Consensual in Right eye (oculomotor intact)

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docarchana
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09/04/06 - 05:34 PM

#10

yup,, ur right..

hope99
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09/04/06 - 09:32 PM

#11

i think A is right answer.

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