OCT eye test

[essdipity]

I seem to have had an OCT test and I didn't even realize it.

During my last exam on July 2, the NP did lots of eye stuff, including having me read a regular eye chart. She turned off the lights and did more looking, with a small gizmo that as I recall looked sort of like binoculars gone wrong, and generally did lots of questioning, peering, and so on. And also, of course, the follow-my-finger thing, etc.

I have never had any eye complaints, though a VEP on the right was abnormal. Last year I asked my neuro about OCT, and he said if the VEP had been abnormal, the OCT would definitely be abnormal as well.

Today I got the notes from that visit. The eye stuff said, in part, that there was no disc pallor. Also, 'VFF, PEARL, no ADP. EOMF, with some jerky saccades.'

I have no idea what all that is, except that the jerkiness may be the same thing as 'Breakdown in smooth pursuit,' which has been noted before.  But on the report, it is noted that an OCT was done.

I gather all this jargon means normal, but I don't know that. Even so, how could the VEP be abnormal if the OCT was good?

None of this is bothering me--lots more things to deal with, and as I say, to me my eyes are fine. Just thought others might be more knowledgeable.

ess

[Quixotic1]

Just passing through on my way back from the loo.

The OCT and VEP do, indeed, measure different things.

The VEP actually measures the functioning of the optic nerve.  It measures the speed with which the nerve transmits its signals of vision.  The VEP can show the damage from Optic Neuritis immediately upon suffering the inflammation of the demyelination.

The OCT doesn't tell us anything about the "functioning" of the nerve.  It measures the "thickness" of the nerve fiber layer right at the very edge of the optic disc.  When the OCT is positive it picks up the fact that some of the nerve fibers have disappeared.  But, during a bout of ON the nerve fibers are still there.  Only in the healing phase do the nerve fibers die off so that there is measurable atrophy.  And not all ON will cause atrophy of the optic nerve.

So, the OCT is good at measuring the cummulative effects of atrophy over time, but the VEP will pick up immediate damage.  Remember that the OCT is not being used for diagnosis, but rather as a reflection of overall central nervous system atrophy.  It is an easier, quicker, and cheaper way to see if the overall brain and spinal cord is atrophying than the MRI.  It's a way to follow our disease over the long haul.

Quix (not really here.  My leg throbs when I leave it down.)

[shoshin]

Ess,

I don't know very much, but I have been reading a little about OCT. I think the VEP and OCT don't measure exactly the same thing.

This article "Optical coherence tomography is less sensitive than visual evoked potentials in optic neuritis" (http://www.ncbi.nlm.nih.gov/pubmed/19564583, free text link in upper right) found that in people with ON, the VEP was better at providing evidence of that than OCT, although some people had a bad OCT without a bad VEP.

* OCT had moderate sensitivity to detect optic nerve changes within the individual clinically affected eye but was inferior to VEPs.

* OCT detected fewer optic nerve changes in the clinically unaffected eye in comparison with VEPs.

* Severe acute ON is associated with a thinner RNFL remotely [so if you had bad ON, your OCT would be worse even after a lot of time had passed]

I think I also read somewhere that maybe there is a gap in time between the initial ON (which would be more likely to show on VEP) and the later brain atrophy, but I think it was speculation so don't hold me to that.

sho

[essdipity]

Thanks for this info, Quix.

Holly, for me there wasn't a target or red dot. I doubt if the NP would get this wrong in putting it into my record since it took a good while, relatively speaking, and the rest of the record seems accurate.

Next time I go, though, I'll ask about this.

ess

[hbananas]

When I had the OCT, I looked into an eyepiece at a target, and a tiny red dot tracked up and down across my field of vision, sort of like what you'd do to fill up an etch-a-sketch screen.

I've had a normal VEP from my prior neurologist (with a weird incomplete report that doesn't say how much the latencies were, but that they were normal--a fill-in-the blank form that wasn't filled in.)

When the MS neuro sent me to the neuro-opth, HE sent me to a retina specialist, who is the one who did the OCT (also normal.)  But in the retina guy's letter, he said my little scotoma might be from a mild bout of ON 13 years ago, even though the VEP and OCT are normal.

Does what I described sound familiar to you?  Or do you think someone messed up your record?

[Quixotic1]

I can't answer your main question.  

PEARL - Pupils Equal And Reactive to Light

EOMF - Extra-Ocular Movements Fine  - jerky saccades are little irregular jerks at the limits of the extraocular movments.  (EOMs at looking up, down, sideways and into the corners)

q