| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York |
| Transcript |
"Today we're going to be talking about band atrophy, and the band is because it runs like a band across the optic nerve. So, here's the normal optic nerve and as you know the fibers from the papillomacular bundle insert right into the disk, and the nasal fibers insert right into the disc. However, the temporal fibers have to go all the way around to insert into the top and the bottom of the disc, and that's because they're trying to avoid going through the fovea. So, the temporal fibers both superiotemporally and inferiotemporally, are at the top and the bottom of the optic nerve, and the nasal fibers, both the papillomacular bundle and the regular nasal fibers, run like a band across the optic nerve. And so, the configuration of the optic nerve is temporal fiber, temporal fiber, nasal fiber, nasal fiber. And so, when we have a field defect that is temporal field defect, or in this case a bitemporal field defect, that's going to translate into nasal atrophy. That nasal atrophy is the nasal fiber because the nasal fiber is the temporal field. And so, that atrophy when it runs across your optic nerve is like a bow tie or a band of atrophy. So, this particular type of atrophy, bow tie or band atrophy of the optic nerve, corresponds with bitemporal field defects, and that implicates a lesion at the chiasm. It's a very, very specific form of atrophy. Band atrophy in both eyes equals bitemporal hemianopsia because it is bilateral nasal fiber loss. And so, you should be worried about band atrophy for a compressive lesion at the chiasm if it's bilateral. The other way the band atrophy comes to us is if the patient has a homonymous hemianopsia, usually an incongruous homonymous hemianopsia. And in that setting, the eye with the temporal field defect, not the eye with the nasal field defect, but the temporal field defect will have the band. And that means there'll be band atrophy in only one eye. One eye will have band atrophy. The other eye will have an hourglass configuration of their atrophy because it's the temporal fiber, and the other eye will have band atrophy. So, the eye with the temporal field defect will have the band atrophy, and so in a right homonymous hemianopsia, that means the right eye has the temporal field defect. That means the right eye is the one that's going to have the band atrophy. The left eye has the nasal field defect, which is going to be the up and down hourglass configuration. And on OCT, we can see this band atrophy. So, it'll be the red zone, but the red will be like a band running across the nerve. So, if you see band atrophy in one eye, look for homonymous hemianopsia. If we see band atrophy in two eyes, look for bitemporal hemianopsia. They both localize to the exact same place, the chiasm or the optic tract, and 98% of the time band atrophy is going to be a tumor." |
