Ok here’s what everybody wants right now, a 9 tweet eyeball education thread:

I saw a patient who came to the ED with sudden painless vision loss. 20/20 in her good eye, could only see hand motion in her not so good eye, so SEVERE vision loss

Thinking the patient had a central retinal artery occlusion (extremely reasonable thought), they started a stroke workup. A CT was done, neuro consult, and they discussed the likelihood of a stroke with the patient. They stopped short of giving tPA and called me.

Hearing the story, CRAO seemed likely, but it could have been a vitreous hemorrhage or retinal detachment or something weird like a lens dislocation. I told them there’s no good evidence for tPA in CRAO and I would come in to see the patient.

Now, in a patient with severe, painless vision loss, the easiest way to tell if it’s a problem that affects the optic nerve (like a CRAO) is to look for a relative afferent pupillary defect (RAPD). It takes 10 seconds to do, it’s free, doesn’t cost anything, and oh yeah it’s free

It’s also easy to learn. As a non-ophthalmologist, you’re not looking for tiny subtle RAPDs, you’re looking for massive, rip-roaring RAPDs you would expect to see in a patient with a CRAO. This is a perfect example. Watch it 1,000 times. You can do this.

So I see the patient. No RAPD. I know right away without using an ophthalmoscope, a slit lamp, or any other medieval torture device, that this is NOT a CRAO. This is not a stroke.

Now I don’t blame the ED staff for getting a CT or any other workup and maybe the CT was done in the ambulance what do I know. I don’t blame them because CRAO was high on the differential, but this easy exam technique could have prevented a bunch of testing.

The patient ended up having a relatively rapid onset cataract. Sometimes people have subacute vision loss (over days to weeks) but discover it suddenly when they check the vision in each eye separately.

When I saw the patient she was terrified about having a stroke. I got to tell her she did not have a stroke but she did need cataract surgery which also terrified her, but in a different way. Anyway, just learn how to recognize an RAPD thank you.