rec.autos.simulators

Polarized glasses epilepsy

Jeffrey Gardn

Polarized glasses epilepsy

by Jeffrey Gardn » Sat, 14 Aug 2004 09:41:22

Would like to hear experiences of anyone here who has succesfully used
polarized glasses to deal with  "simulator sickness"
issues/photosensitive seizure etc.
Thanks!

(little background reading follows)

"Cross polarized spectacles in photosensitive epilepsy.

Jain S, Woodruff G, Bissessar EA.

Department of Ophthalmology, Leicester Royal Infirmary and Northampton
General Hospital, United Kingdom.

PURPOSE: To investigate the role of cross polarized spectacles in the
treatment of photosensitivity demonstrable by EEG. METHOD: Patients
receiving an EEG who tested positive for photosensitivity were invited
to participate in the study. The most sensitive light flicker
frequency causing a photic response was determined for each patient.
Stimulation was repeated with 2 different pairs of spectacles--1
conventionally polarized and the other cross polarized. An EEG was
obtained in each case and reported by a neurophysiologist who was
unaware of the identity of the 2 types of spectacles. RESULTS: We
tested 19 patients, 8 to 18 years of age. Two patients did not benefit
from either pair of glasses. In 17 patients, the photic response was
greatly diminished or eliminated by polarizing spectacles. In 1
patient, conventional polarized glasses helped, but the cross
polarized spectacles did not. In 6 patients, both types of spectacles
were equally effective; in 10 patients, cross polarized spectacles
were more effective than conventionally polarized spectacles.
CONCLUSION: The role of cross polarized spectacles in the management
of photosensitivity in a clinical situation merits further
investigation."

simps

Polarized glasses epilepsy

by simps » Sun, 15 Aug 2004 01:59:22

A polarizing filter will only make a difference when the light
arriving at your eyes is predominately polarized like when you look at
light reflected off an angled reflecting surface.  In that case, a
polarizing filter can cut out the reflecting light in one axis (p or s
- parallel or perpendicular to the plane of incidence of which the s
polarization is the strongest).  Light from a CRT is randomly
polarized (or unpolarized).

So unless you have a monitor at a sharp angle to a high intensity
light source which causes high reflections, a polarizing filter will
just cut out about 40 - 50% of the light coming to your eyes, like a
pair of sunglasses.

Now if your talking about an LCD, which relies on polarized liquid
crystals, the polarizer will make the screen look black since the
polarized crystals send out images as polarized light.

Your quoted article sounds a little fishy to me.  I'm not an expert
(I'm a lab technician in an optical thin films research lab) but I use
a cross polarizer to simply reduce (unpolarized) light to different
levels.  Fully crossed they eliminated almost 100% and if the
polarizers are parallel, about 50 60% is eliminated when looking at
a very bright light.  I don't see what they're looking at that might
be polarized.  It says: "light flicker frequency causing a photic
response" and I don't see how flickering frequency and polarization
are related.

Bob Simpson


> Would like to hear experiences of anyone here who has succesfully used
> polarized glasses to deal with  "simulator sickness"
> issues/photosensitive seizure etc.
> Thanks!


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