Re: Tunnel Vision

I can think of three conditions that can cause tunnel vision. The first one
is a transient decrease in blood pressure which results in decreased blood
flow to the sides, top and bottom portions of the retina that form
peripheral images. This is temporary and not dangerous. (When my blood
pressure drops, I get a top and bottom "closing window-shade" loss of
vision, but I have talked to lots of people that get the "tunnel".)

 A second cause of permanent loss of peripheral vision (leaving only the
central visual field or "tunnel vision") is glaucoma. Glaucoma causes its
damage in the optic disc, which is where the nerves from the retina exit
the globe of the eye to form the optic nerve. Glaucomatous visual losses
result from an increase in the pressure inside the eye (intraocular
pressure) which causes the optic disc to bulge out. At first this
selectively kills the nerves that come from the peripheral portion of the
retina. At this stage the person will have tunnel vision. At later stages
blindness could occur. Third, any eye disease that selectively interferes with the
peripheral portions of the retina could cause tunnel vision.

Glaucoma is generally treated with medicines that lower intraocular
pressure or with surgery that create openings in the globe or within
critical structures within the eye. Once glaucoma causes visual field loss,
the loss is generally permanent. The obvious goal is to detect the glaucoma
first, so that permanent loss can hopefully be prevented.

Sincerely,
David Winsemius, MD, MPH

David Winsemius, MD, MPH(epidemiology) |
dwinsemius@imagine.com                 |
dwinsemius@aol.com                     |