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Retired NBME 19 Answers

nbme19/Block 3/Question#5 (reveal difficulty score)
30 yo woman, 1 week of visual difficulty
Right optic nerve ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–
tags: RAPD ophtho

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 +5  upvote downvote
submitted by โˆ—aliyah(51)
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The right eye's efferent nerves are working, as left eye stimulation causes a change in the right eye. The right eye optic n. damage causes it's afferent n. to be damaged. It can't carry info to brain, so right and left eye can't constrict to light.

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icedcoffeeislyfe  APD--> swinging flashlight test, light in the AFFECTED eye will result in dilation of both pupils inappropriately +1
cbay0509  thank you +
nbme_123  Can someone please explain why it cant be the Right Edinger Westphal nucleus? +1
chaosawaits  But if right optic nerve doesn't work, why does it dilate normally in the dark to 6 mm? +1
pakimd  @nbme_123 im not sure if im correct but i think the reason why right edinger westphal nucleus is not the correct answer is because the left edinger westphal nucleus sends one axon to the right edinger westphal nucleus and one to right pretectal nucleus so that way damage to right edinger westphal will still result in relaying of efferent innervation to the right eye +
unknown001  before you read , look at the picture i am posting . then slowly trace the pathway. ( open to corrections) recomendation : open the pic by memorang https://www.google.com/search?q=optic+nerve+edinger&rlz=1C1CHBF_enNG840NG840&sxsrf=ALeKk01M2EGnC0HOchexNuok-0qKdtFuBQ:1609541285076&source=lnms&tbm=isch&sa=X&ved=2ahUKEwje-7DE6PvtAhUOSq0KHbSwDLsQ_AUoAXoECAUQAw&biw=1280&bih=578#imgrc=gEsVR5pPWG5WLM EXPLANATION PROPER information from rt. optic nerve first relays at right pretectal nucleus. @right pretectal , the fibers are split into to relay at left and right edinger westphal . this is the reason why i think if rt. edinger westphal is damaged, and you shine light in the right eye, the left pupil will constrict, solely because of suply from the right pre tectal. +



 +2  upvote downvote
submitted by danitex(2)
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Marcus Gunn Pupil. FA 2020 pag 539. Damage of light signal due to injured optic nerve.

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