| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (JJV) Class of 2021, Baylor College of Medicine, Houston, Texas |
| Transcript |
Today we're going to be talking about monocular diplopia and normally monocular diplopia is not a neuro-ophthalmic problem because normally that means the problem is in your eye. And so the first question we want to know in monocular diplopia, is it really one eye? Now, to determine whether it is monocular diplopia, we are going to ask the patient if it goes away, but not if you cover one eye, if you cover either eye. Because if they cover the eye that has the monocular diplopia, they will say," Yes, it went away." and that's still monocular diplopia. So, it is either eye, so they will respond if they cover the affected eye, the monocular diplopia will go away. If they cover the unaffected eye, the monocular diplopia will persist. And usually it is described as a second ghost image that is superimposed on the first image. They are not really clear and separated two images. And so that kind of ghosting or second image that is unclear is a tip-off that it is monocular [diplopia]. Now, monocular diplopia can be bilateral or unilateral. And so, if they have it persist with covering one eye, or the other eye, and it is in both eyes, that is bilateral but monocular [diplopia] versus if it only goes away if you cover one eye and does not go away if you cover the other eye, that is a unilateral monocular diplopia. And so, when we have monocular diplopia, one of the first things we should do is deploy the pinhole test. So when we put the pinhole up, as you know, the rays of light coming in, only the one ray is going be allowed to go through and by blocking the extra rays of light, we can prove that the optical system is what is causing the monocular diplopia. The patient either [has] a dry eye, or cataracts, or something in the cornea, or in the retina. So, the pinhole is a super great, and fast way to prove that something is optical and monocular diplopia. So, in most cases, binocular diplopia is not neuro-ophthalmic and requires a slit lamp and looking at the front of the eye, and a cataract evaluation, and refraction, and so we don't really image or test other people for monocular diplopia. So, if it is binocular diplopia, that is neuro-ophthalmology and that does need a work-up for the usual suspects: nerve, muscle, and junction. However, the one monocular diplopia that you have to think about is if it is a bilateral monocular diplopia, and if it is exactly the same in both eyes, then we would be worried that you might have cerebral diplopia and that cerebral diplopia can be multiple images of the same thing over and over again. That is called palinopsia. Or it can actually be cerebral polyopia when have a repeat of the image: triplopia, quadroplopia, or whatever. And those patients usually have a structural abnormality. We are going to do a Humphrey visual field in that person looking for a homonymous hemianopsia. And, so the cerebral cases usually have a known cause. So, the bottom line is, monocular diplopia: ask if it goes away with covering either eye. It can be bilateral monocular or unilateral monocular. If it is unilateral and monocular, we do the pinhole and we do the slip lamp and look at the eye exam because monocular unilateral is in the eye. Make sure it is not bilateral cerebral polyopia or palinopsia and if it is not that, that is not neuro-ophthalmology. |
