Re: Restoring Lost Vision

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Halterb - 21 Dec 2004 01:46 GMT

Ann responded to the Restoring Lost Sight article by saying:

>The article says the device is used for stroke or brain-injured
>patients. I assume their optic nerves are still OK, but parts of the
>brain were damaged. Perhaps, as with other functions, other parts
>ofthe brain can be trained to take over. I doubt this could help
>restore vision lost to Glaucoma, since the optic nerve cells are gone.
>Would be nice if something so simple as this could help us!<

This starts to get into the physiology of vision. It's my understanding that
the label "optic nerve" isn't accurate--it's sometimes referred to as the
"optic stalk," an extension of the brain, not really a "nerve" in the usual
sense, and particularly subject to injury by lack of blood circulation (with
the resulting lack of oxygen). Evidently even low blood pressure can cause this
sort of injury, as well as constriction of blood vessels. I suspect that is at
least part of the reason for good results in some cases with this approach.

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tom - 22 Dec 2004 03:16 GMT

> Ann responded to the Restoring Lost Sight article by saying:
>
[quoted text clipped - 12 lines]
> sort of injury, as well as constriction of blood vessels. I suspect that is at
> least part of the reason for good results in some cases with this approach.

This has me wondering why epinephrine is a drug
used to treat glaucoma.

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Halterb - 22 Dec 2004 11:14 GMT

Tom replied:

>This has me wondering why epinephrine is a drug used to treat glaucoma.<

Not sure just what Tom picked up on my my last post--maybe it was my comment
about low blood pressure or constriction of blood vessels having the potential
to cause damage.

My understanding is that epinephrine improves circulation to the visual
apparatus. Quite a long time ago it was used in conjunction with medication
that constricts the pupil (pilocarpine). Although some on this newsgroup
disagree, other sources claim constriction of the pupil tends to open up the
drainage pathways out of the eye allowing pressure to be reduced.

Epinephrine, being involved in action of the adrenal system, seems to be
naturally released in the "fight or flight" phase of reaction to stress,
dilating certain blood vessels increasing blood (and oxygen) circulation, while
also dilating the pupil to theoretically improve vision at the moment,
perversely increasing eye pressure. Medication to constrict the pupil was added
to block the pressure increase, while allowing improved circulation to
continue.

(I should add that I am only a glacoma patient and do not have any medical
training.)

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