Marcus Gunn Pupil and Argyll Robertson Pupil – Pupillary Disorders

by Richard Mitchell, MD

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    00:01 Okay.

    00:02 Again, just to review.

    00:04 So when we have light shining in one eye, we get a direct light reflex and we have had a consensual light reflex in the other eye because of that signaling going through the Pretectal nucleus and Endinger-Westphal nucleus, the ciliary, you know, cranial nerve, all that stuff, okay.

    00:22 Direct and consensual.

    00:24 But there are some lesions that prevent that from happening.

    00:28 So if you have abnormal processing in one eye.

    00:31 So the normal eye is being shined, the light is shining there and we have a good direct light reflex.

    00:38 And we have miosis in the other eye, a consensual light reflex.

    00:42 Now, I'm telling you that the patient's right eye, on the left-hand side here, the right eye has got abnormal processing of light, it's not going to understand exactly how it should respond.

    00:54 So I shine the light in that eye remove the flashlight over, there it goes.

    01:00 And I only get a little tiny bit of reflex and not only that I'm not getting any direct reflex, I'm not getting consensual.

    01:08 So as it goes back and forth, see that we lose the direct and consensual light reflex because of abnormal processing in that right eye.

    01:17 What's going on here? Well, this is the Marcus Gunn, so-called Marcus Gunn Pupil named after Dr. Marcus Gunn, who discovered it, he should have named it after his patient, but he named it after himself.

    01:28 And what is going on here is that we have a defect in the optic nerve or in the retina of the abnormal eye.

    01:36 So again, the right eye here has got a defect and you see it as a big X there in the optic nerve, it can also be in the retina on that side.

    01:44 And when the light shines in that abnormal eye, or the abnormal optic nerve, I don't get the director consensual response.

    01:53 But when I go down to the normal eye at the bottom where everything is intact.

    01:59 Perfect, good.

    02:01 So this is an Afferent defect.

    02:03 Afferent processing defect, meaning coming off the eye.

    02:06 The problem is very proximal in the entire chain of things.

    02:11 So possible etiologies for Marcus Gunn Pupil.

    02:14 You can have lesions of the optic nerve and the visual path pathway very proximal to the eye.

    02:20 You can have lesions of the retina in that eyes, so it's not perceiving light appropriately.

    02:25 We could have a patient who's developed Amblyopia.

    02:27 Remember, this is central brain failing to process information that's being sent by the eye.

    02:35 We had a whole session where we talked about amblyopia and strabismus, right remember? Go back and review.

    02:41 And you can have eyes that have, they're not always perfectly matched in terms of the diameter of the pupil.

    02:48 And some people walk around with one people bigger than another and that's just their normal state.

    02:53 So they may have an apparent Marcus Gunn Pupil.

    02:57 Okay, that's Marcus Gunn.

    02:58 Let's look at one other way that we can mess up the pupillary response.

    03:02 This is the Argyll-Robertson Pupil.

    03:05 And this is the green box at the top is typically classically associated with syphilis.

    03:11 And the syphilitic lesion will occur in the Eringer-Westphal nucleus.

    03:16 Actually just a little bit dorsal to that.

    03:19 So that little spiral gates responsible for the syphilis are getting in that area where we have the X.

    03:26 So now what is happening, we shine the light and none of that information is getting through.

    03:31 So light doesn't make the pupils respond.

    03:35 They're non-responsive to light either as the direct or the consensual response.

    03:41 But see, when the fly goes in, the eyes rotate towards that, that's accommodation.

    03:47 And normally when eyes come close and look at something close to the nose, such as that fly coming in.

    03:53 Then the pupils do also undergo miosis.

    03:58 That's to limit the amount of light.

    03:59 You don't need as much light when you're looking up close.

    04:02 So the pupils in these patients with Argyll-Robertson due to the syphilis involving the Edinger-Westphal nucleus, don't respond but they do accommodate.

    04:14 So in a less politically correct time, many many years ago, when I was a medical student, the way that we remember this, was that okay this is a disease associated or a lesion associated with syphilis, the Argyll-Robertson Pupil.

    04:29 And in Argyll-Robertson Pupil, the pupils don't respond but they accommodate and because of association with syphilis, the way to think about this and remember this was that it was like a lady of ill repute who would accommodate you but wouldn't necessarily respond.

    04:48 So that's a less politically correct environment.

    04:51 I'm not even sure that joke is going to make it into the final cut, but hopefully it will.

    04:55 And now we've talked about Marcus Gunn, Argyll-Robertson, miosis, mydriasis.

    05:00 You've learned some other drugs.

    05:01 And we'll quit there.

    05:03 Thank you very much.

    05:04 See you later.

    About the Lecture

    The lecture Marcus Gunn Pupil and Argyll Robertson Pupil – Pupillary Disorders by Richard Mitchell, MD is from the course Diseases of the Anterior Chamber and Uvea.

    Included Quiz Questions

    1. Both direct and consensual
    2. Only direct and not consensual
    3. Only consensual and not direct
    4. Neither direct nor consensual
    5. Possibly direct or consensual
    1. The retina or optic nerve
    2. The retina or optic disc
    3. The retina or cornea
    4. The retina or optic fovea
    5. The retina or pupil
    1. Anisocoria
    2. Anisocytosis
    3. Atrophy
    4. Anisopoikilocytosis
    5. Anisokaryosis
    1. Edinger-Westphal nucleus
    2. Pretectal nucleus
    3. Oculomotor nerve
    4. Ciliary ganglia
    5. Optic nerve
    1. Syphilis
    2. Tuberculosis
    3. Leprosy
    4. AIDS
    5. Pneumonia

    Author of lecture Marcus Gunn Pupil and Argyll Robertson Pupil – Pupillary Disorders

     Richard Mitchell, MD

    Richard Mitchell, MD

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