| Identifier |
coloboma_of_optic_nerve_lee |
| Title |
Coloboma of Optic Nerve |
| Creator |
Andrew G. Lee, MD; Nadia Ansari |
| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (NA) Class of 2022, Baylor College of Medicine, Houston, Texas |
| Subject |
Optic Nerve Coloboma; Embryology |
| Description |
Summary: • In embryology, the eye beings as a vesicle > stalk outpouching that forms optic cup > forms the back part of the eye (optic nerve) • Surface ectoderm invaginates to form lens placode > forms the front part of the eye o Lens placode pinches off > lens vesicle > surface = cornea • The choroidal fissure of the optic cup is the last segment to close and does so in the sixth week of gestation, and the failure of this closure leads to coloboma of the optic nerve o In a coloboma there is a piece missing such as the surrounding retina or RPE • This is something that you are born with and is important for two reasons o (1) It can lead to a superior visual field defect with loss of visual acuity o (2) Can affect the formation of the eye and lead to amblyopia or nystagmus • If a coloboma forms anteriorly it can affect the iris or pupil, but if it occurs posteriorly it can affect the retina, RPE, or the optic disc • In patients with colobomas, it's important to perform an MRI due to the higher probability for additional closure problems in the midline that could potentially affect the hypothalamic-pituitary axis or cause a basal encephalocele. |
| Transcript |
So today we're going to be talking about coloboma. It's a coloboma of the optic nerve that we're most interested in, but the coloboma can occur anywhere along the eye pathways. Sometimes it's in the iris, and it can make it a keyhole pupil in your iris. But today we're going to be focusing on the optic nerve. So, as you know in embryology, the fissure closes at about the sixth week of gestational age. It starts off as a vesicle and then there's a stalk outpouching, and that makes a cup. And this optic cup becomes the back part of the eye. And the front part of the eye is going to be formed by the surface ectoderm that's going to invaginate and form the lens placode. And that lens placode will pinch off and become a lens vesicle and the surface will become the cornea. The back part of the eye is going to be the optic nerve. This optic cup is going to close -- and it closes in this manner -- so that this is the last portion to close. The hyloid vessels are going to enter into that fissure. This choroidal fissure will close - that closure is complete somewhere in the sixth week. And failure of this fissure to close, the choroidal fissure, will lead to the ophthalmoscopic finding that we call the coloboma. The optic nerve would normally be round like this, but when you have coloboma there is a piece missing - and maybe the surrounding retina and RPE are also missing so the failure of this closure of the optic cup, the failure of the choroidal fissure, to completely close inferiorly usually leads to the coloboma. You're born with this. The reason it's important is because 1) you can have a superior visual field defect from this inferior closure deficit where you might have lost some acuity, and 2) it can also affect the formation of the eye and cause amblyopia or nystagmus because the vision is quite variable in these patients with colobomas. It can be all the way anterior to the keyhole/pupil anteriorly and it can affect the retina, the RPE, and the optic disc itself. The other reason to know it is because you should do an MRI on these people because the same kind of closure problems can occur in the midline and affect the hypothalamic-pituitary axis and can also lead to encephalocele, a basal encephalocele - where brain is protruding down through the basilar skull defect. You need to know about coloboma, a little bit about the embryology (the vesicle, the stalk, the cup, and the choroidal fissure) the closure at the sixth week of gestational age. Coloboma is usually inferiorly as a result of this, and it can be retina, choroid, or the optic disc. It can extend anteriorly to the iris. And you should do an MRI to make sure there's not a basal encephalocele. |
| Date |
2021-04 |
| 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 |
| Rights Management |
Copyright 2019. For further information regarding the rights to this collection, please visit: https://NOVEL.utah.edu/about/copyright |
| ARK |
ark:/87278/s68q1x4k |
| Setname |
ehsl_novel_lee |
| ID |
1680594 |
| Reference URL |
https://collections.lib.utah.edu/ark:/87278/s68q1x4k |
