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  • From: Sil Greene <Sil_greene AT unc.edu>
  • To: "Internetworkers: http://www.ibiblio.org/internetworkers/" <internetworkers AT lists.ibiblio.org>
  • Subject: Re: [internetworkers] odd question - optometric stuff
  • Date: Wed, 17 Dec 2003 18:43:05 -0500 (EST)


Paula, I forwarded your question to a friend of mine who's almost through
optometry school. Here's her response:

================================================
Date: Wed, 17 Dec 2003 19:57:03 +0000
From: Beth <snip>
Subject: RE: odd question - optometric stuff (fwd)

heh heh, right up my alley....

So your friend was right, -5.25 is the diopter value that she needs. 
However, there is minimal difference between -5.00 and -5.25, and the
same goes for -5.25 versus -5.50.  This is the reason that they are sold
in half dipoter increments:  it's such a small difference, few people
will notice, so doing this cuts down on production by an unbelievealbe
amount.  Some cantact lens manufacturers do the same thing, and in
reality it works out well.

Now for her question:  Since she is -5.25, -5.00 is a little weak and
-5.50 is a little strong.  The funny thing is, your focusing system can
make up for lenses that are a little too strong, and you can still get a
focused image on your retina (this is why nearsighted people HAVE to have
glasses to function, but you rarely see farsighted people walking around
with glasses unless they're older).  So this part is up to her:  if a
little bit of blur will drive her crazy, go for the stronger power.  If
she doesn't mind a little haziness, go for the weaker power. This is IF
the -0.75 and the -0.25 IS INCLUDED.

As for the -0.75 x 090 and the -0.25 x 090, this is the amount of
astigmatism in the eye.  So her right eye is a little more astigmatic
than her left (Think of the eye like a graph. The astigmatism just means
that the "x" axis of her eye has more perscription than the "y" axis). 
Now I'm not sure if these swim goggles come with astigmatic correction in
them, but I'm doubting it.  I'll spare you the optics of it, and just
tell you that I averaged the two powers together for each eye and came up
with this:  OD: -5.50 DS, OS: -5.25 DS (remember, this is if the
astigmatism is NOT included in the glasses).  Now, tell her that this
won't be perfect, but you don't really have to pay a great deal of
attention to detail while kayaking and rafting, so I don't think it will
bother her. 

So, long story short, tell her to go with -5.50 for the right eye and
-5.25 for the left eye.  If they have to be the same for each eye, go
with the -5.50.  Tell her to keep the receipt if she's not sure if a
little bit of blurriness will bother her (that's the beauty of this job,
you never know who is going to come back and yell at you *s*). 

Hope this helps out a little and wasn't too confusing.
=======================================================




Reported 03.12.17 11:22 from childers.paula:
.:OK, so this is REALLY not a computer-techie related question, but this
.:is such a diverse group, I thought it worth asking - perhaps one of you
.:is married to an opthamologist or something...
.:
.:I need to buy a pair of prescription swim goggles, and it seems that the
.:places that sell them only sell lenses in ".5 diopter" increments. I
.:have a card with my prescription on it, that says:
.:
.:OD -5.25 -75 x 090
.:OS -5.25 -25 x 090
.:
.:I'm presuming the "-5.25" is my "diopter," which means I am in a
.:dilemma. Do I order -5.0 lenses, -5.5 lenses, or one of each (if the
.:"-75" etc. stuff is relevant)? Which is going to be better?
.:
.:If it helps, I will be using the goggles for kayaking and rafting.
.:Better to have something that won't fall off if you roll over, and those
.:little croakie-tie straps just don't cut it.
.:
.:Paula

--
"If you put your supper dish to your ears you can hear the sounds
of a restaurant." --Snoopy (Charles Schultz 02-12-2000 RIP)
Sil_Greene AT unc.edu






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