Day Blindness Relating to Colour Blindness? Posted: 02-02-05 02:17am
I have a question that has been bothering
me for some time now. Does day blindness
(hemeralopia ) relate to colour blindness.
I'm colour blind and I have spectacular
night vision, but horrible day time
vision. In bright light I cannot see at
all, when I drive I even during regular
light levels I have to squint because its
to bright and when i'm kayaking on
overcast days I have to squint. Anyway I
am also colour blind so do these two
conditions relate to each other in any
form?
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Gary13
New User, Becoming EHEALTHy
Joined: 31 Jan 2005 Posts: 12 Location: Austin, Texas
Cones & Rods Posted: 02-04-05 20:41pm
Color blindness, day blindness, and good
night vision may have something to do with
the normal or abnormal operation of the
rods & cones in your retina.
The eye perceives color using the "cones,"
cells in the retina named after their
shape. If I remember my physiology
correctly--and someone step on my foot if
I don't--there are red/green cones and
blue/yellow cones. Red/green color
blindness is most common, blue/yellow less
common, and complete color blindness least
common of all.
Brightness without color is sensed by the
rods. We rely on the rods for night
vision, and I believe that rods outnumber
cones towards the edge of sensing portion
of the retina. I believe that with the
rods one may actually have better visual
acuity. Motion detection also depends
more on rods than cones. (again, I could
be getting this only half right, but this
is what I recall.)
as to having your vision "saturate" during
the day, i'm not sure what the cause may
be. I'd guess that your pupils are too
wide open, which may be a problem of the
brain misreading the intensity of ambient
light. Other than that my only guesses
would be that your cones & rods are
more sensitive to light than those of
other people, but i'm not even sure how
much sensitivity can vary. There are
eyedrops to dilate (widen) the pupils, but
i'm not sure if there are eyedrops to
constrict them. In any cases the pupils
need to respond very quickly to changes in
light levels, and they're much better at
this than your typical video camera.
You may already wear dark sunglasses or
dark wraparound sunglasses during the day
to compensate. If not, consult an
optometrist about the wisdom of doing so.
By wearing sunglasses your pupils are
likely to widen to compensate. Be certain
to wear sunglasses with lenses made from
polycarbonate or from some other material
that blocks 99% of uv-a and uv-b light.
In software it's a simple matter to
convert a color image (or color video) to
black & white, but i'm not aware of
any material that can do this to light.
For more info on this and other subjects,
check out the open source online
encyclopeida wikipedia at www.Wikipedia.Com.
- gary
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Miromc
New User, Becoming EHEALTHy
Joined: 13 Nov 2004 Posts: 4
Posted: 02-04-05 21:19pm
Thanks for the reply.
I do wear my sunglasses a lot when I drive
now, I just can't stand squinting
anymore.
I should probably go to an optamitrist one
day, its been about 10 years since i've
been to one.
I'm kind of disappointed that the 2
conditions aren't related. I wish it was
just a problem with the cones or the rods,
not both. Oh well. I've got good
eyesight so I don't care having horrible
day vision or loss fo colour. The day
blindness isn't extreamly bad, but enough
that it forces me to squint whenever i'm
outside on a clear day.
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Gary13
New User, Becoming EHEALTHy
Joined: 31 Jan 2005 Posts: 12 Location: Austin, Texas
Neutral Density Contact Lenses Posted: 02-04-05 21:26pm
Here's a wacky idea:
is there any chance you could get tinted
contact lenses? I'm not sure if it's
possible or even safe, but it's a thought.
Ideas less wacky:
rather than seeing an optometrist, you may
wish to see an ophthalmologist, especially
if you haven't had an exam for a decade.
I'm certain that with a little searching
you could find someone who has studied and
perhaps even treated your condition.
The difference in brightness between a
bright, sunny day and the indoors is
greater than we usually perceive it to be
since the pupil adjusts very quickly.
Perhaps there's a "ceiling" to the
brightness you can tolerate without
sunglasses, and you hit this ceiling only
on sunny days and perhaps (?) when you
look into very bright lights.
Good luck to you.
- gary
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tanya11
New User, Becoming EHEALTHy
Joined: 30 Jan 2005 Posts: 9
Posted: 02-05-05 16:44pm
What type of colour vision defect do you
have?
Are you extremely sensitive to the light
or is it just an annoyance?
You have three types of cones. They
respond maximally to short, medium, and
long wavelength light. They respond
maximally in high lighting conditions (ex
daytime). These are the receptors that
are affected in colour vision defects.
Typically, one of the receptor types is
deficient or missing giving rise to one of
three colour vision defects (commonly
known as red/green or blue/yellow).
Usually the missing/deficient receptor is
replaced by one of the other types thus it
does not normally affect your light
sensitivity just your perception of
colour, except in severe defects.
You also have rods, which respond
maximally in low lighting conditions.
These are not responsible for your colour
vision hence your night vision is
unaffected. These receptors saturate in
high lighting conditions.
There is complex interplay and inhibition
between these two pathways. But, unless
your colour vision is severely affected
(pretty much see in greyscale) this
shouldn't be the reason for your light
sensitivity. Some people are just more
sensitive than others.
I would suggest a good pair of sunlasses,
unless you have a severe defect in which
case different filters would be
beneficial.
Hope this helps.
Ps. Don't hesitate to see the
optometrist if this bothers you -- they
are trained to, and do, deal with these
types of problems all the time.
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Miromc
New User, Becoming EHEALTHy
Joined: 13 Nov 2004 Posts: 4
Posted: 02-06-05 02:29am
It depends on whether it is merly an
annoyance or actually extreamly sensitive.
Most of the time its just an annoyance,
but tehre are days where its actually
painfull to go outside without squinting,
especially in the winter or when i'm
kayaking. Now that I have done a little
more research on the topic I think I am
just overly sensitive to light. Not
enough to really considered a condition,
but enough that it does get annoying. It
is actually beneficial in a way because as
I said before I have excellent night
vision, and i'm also an amateur astronomer
so its great for that.
As for the colourblindess type, I think
(i've never been formally diagnosted by an
optomitrist) I have protanomaly, which is
red-weakness. I am thinking of going to
an optomitrist soon to ask about the
colour blindness. It has started to
affect my university work. Colour coded
maps are becoming dreadfully evil to try
and read, and my geology labs are
suffering.
