| Identifier |
non_paretic_diplopia_Lee |
| Title |
Nonparetic Diplopia |
| Creator |
Andrew G. Lee, MD; Lauren Nakhleh |
| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (LN) Class of 2023, Baylor College of Medicine, Houston, Texas |
| Subject |
Diplopia; Nonparetic; Double; Exotropia |
| Description |
Summary: • Nonparetic Diplopia occurs when you have double vision, but no weakness of any muscle or nerve o Prototype = patients who do not have overlap in their field o Classic example = patients who have a pituitary tumor with bitemporal hemianopsia -the nasal fields can slide past one another and cause hypertropia, or separate if you have an esotropia or exotropia -additionally, patients with a pre-existing phoria can break their fusion if they have a nonparetic diplopia • Other forms of Nonparetic Diplopia: subretinal neovascular membrane or epiretinal membrane o Causes the fovea to shift out of center, leading to a central vs peripheral rivalry o Can be determined by having the patient look straight ahead and seeing if the diplopia is the same with the lights on or off -With the lights off you are just lying on central vision • Another type of nonparetic diplopia is supranuclear palsy o One of the most common causes at near is convergence insufficiency, causing exotropia due to age or illness o Very common cause of diplopia at near • Other factors that can cause nonparetic diplopia: micropsia, macropsia, hemifield slide phenomenon, and torsion (hard to fuse a tilted image on top of a straight image) • Horror Fusionis = occurs when patients have lost the supranuclear control of fusion |
| Transcript |
So today we're going to be talking about nonparetic diplopia which is a very counterintuitive subject. Basically, you have double vision, but you don't have any weakness of any muscle or nerve. It's a non-heretic, no weakness, diplopia. The prototype for nonparetic diplopia is patients who don't have overlap in their field. The classic example is patients who have a pituitary tumor who have a bitemporal hemianopsia. So, in a patient who has a bitemporal hemianopsia what they really have is a juxtaposed nasal field. The nasal field of one eye overlaps with the temporal field of the other eye. When you have a bitemporal hemianopsia you actually don't have any overlapping field because your temporal field has been lost. When you have these juxtaposed nasal fields, they can slide on one another and cause a hypertropia. They also can separate or overlap if you have an esotropia or an exotropia. So, patients with a pre-existing phoria can break their fusion if they have a nonparetic diplopia. The other forms of nonparetic diplopia that you should be thinking about are when you have a subretinal neovascular membrane or an epiretinal membrane. As you know in your eye your fovea is the center part of your vision. Conditions which move this fovea either like an epiretinal membrane or a subretinal neovascular membrane cause the fovea to not align. So, the central vision is not aligned with the peripheral vision. There is nothing wrong with the nerves or the muscles or the junction. It is a central versus peripheral rivalry. When you have a rivalry between the fusion of your peripheral field and your fovea because one fovea being displaced, then the patient has non paretic form of the diplopia. There is no weakness. It is just that the two lines are not aligned on target. We can determine this by having the patient look straight ahead and seeing whether diplopia is the same with the lights on or the lights off. With the lights off you've taken away the peripheral vision, so they are relying only on the central vision. So, patients with central versus peripheral rival really have to choose to fuse one or the other. Another type of nonparetic diplopia is when you have supranuclear palsy. So supranuclear palsy can disrupt your fusion. There's nothing paretic or weak around your muscles. It is just that you can't make the two images come together. One of the classic causes of the fusional deficits at near is convergence insufficiency. As you get older or if you're sick for any reason you're not able to converge. That will cause the eye to drift out, exotropia. So, convergence insufficiency is a fusional problem at near. This is a super common cause of diplopia at near. But there are other things that can disrupt your fusion. Anything that makes you sick or disrupts the fusion can cause the image to split. So, if the two images are not the same in anyway then you won't be able to fuse them. So, if one image is smaller or one is bigger, micropsia and macropsia, then you will not be able to fuse them. If the two images aren't overlapping like in the hemifield slide phenomenon or if you can't fuse the central versus peripheral because they're not in the same location. Those all will cause fusional problems. In addition, torsion…so if the image is tilted, it will be hard to fuse a tilted image on top from a straight image. So, the torsion alone might be the barrier to fusion. Finally, some patients simply have lost the supranuclear control of fusion This is called horror fusionis. So, when you can't fuse even with your eyes aligned, that is horror fusionis. It is like horror like a horror movie and fusionis…you cannot fuse. So, if you just know these nonparetic forms of diplopia: the hemifield slide phenomenon, retinal ideologies that move the fovea, central versus peripheral rivalry, supranuclear fusional abnormalities and the horror of horror fusionis, you know the nonparetic forms of diplopia. |
| Date |
2019-10 |
| Language |
eng |
| Format |
video/mp4 |
| Type |
Image/MovingImage |
| Collection |
Neuro-Ophthalmology Virtual Education Library: Andrew G. Lee Collection: https://novel.utah.edu/Lee/ |
| Publisher |
North American Neuro-Ophthalmology Society |
| Holding Institution |
Spencer S. Eccles Health Sciences Library, University of Utah, 10 N 1900 E SLC, UT 84112-5890 |
| Rights Management |
Copyright 2019. For further information regarding the rights to this collection, please visit: https://NOVEL.utah.edu/about/copyright |
| ARK |
ark:/87278/s6rc1w25 |
| Setname |
ehsl_novel_lee |
| ID |
1469309 |
| Reference URL |
https://collections.lib.utah.edu/ark:/87278/s6rc1w25 |
