This is my first post to the group. I have a patient that I am having a
difficult time with and I am trying to find some answers from fellow
professionals, please.
We first saw "Cat" 7 years ago. She was a -2.75 OD and -2.50OS. She was
about 15 then so as is our policy we put her in polycarbonate lenses. When
she complained of "color bands" and described them perfectly we assumed the
poly was the problem. The Dr. decided to try Spectralite lenses but the same
problem occurred. So we put her in CR-39 and she was fine. A year or so
later she started contact lens wear.
"Cat" decided this year to update her glasses and put new lenses into an
existing frame. Her RX is now -5.00-0.50 X 130 OD and -5.25 OS. I kept her
in CR-39 lenses with no lens polish. Her complaint of color bands came up
again. I tried readjusting the frame, I sent the glasses to the lab to check
for flaws but none were found. They decided to remove the TD2 scratch
coating just in case. Still she described color bands. My last ditch effort
was to have the lenses remade with Crizal Alize. Still she has the same
problem.
I have no idea where to go next. We could try to change frames to one with a
thicker rim, we could try glass lenses but they'd be so heavy, I even
thought about a colored lens treatment around the outside of the lens. She
is in a full rim metal frame......same frame she has worn for 7 years. I
would appreciate any help you could give me. The Dr. is running out of
patience, I am running out of ideas and the patient just wants a pair of
glasses she can see out of.
Thanks in advance,
Laura, A.B.O.C.
Her RX is now -5.00-0.50 X 130 OD and -5.25 OS. I kept her
> in CR-39 lenses with no lens polish. Her complaint of color bands came up
> again.
Are you sure they are cr39? I mean if so, then it almost can't be
chromatic aberration. Make sure someone didn't inadvertently do poly
when you weren't looking. Other than that, make sure your p.d.s are
right on. Does she only see them in the lens periphery? If you strike
out completely, there's always contact lenses.
w.stacy, o.d.
Robert Martellaro - 20 Jun 2005 18:32 GMT
> Her RX is now -5.00-0.50 X 130 OD and -5.25 OS. I kept her
>> in CR-39 lenses with no lens polish. Her complaint of color bands came up
[quoted text clipped - 7 lines]
>
>w.stacy, o.d.
Right. It's either the material or the fit. The change to Spectralite should
have solved the problem but remember that this is an aspheric design with low
tolerance to errors in lens positioning. Check the monocular PDs, panto, and
vertical OC height. Sounds like this client is extremely sensitive to these
aberrations. Post back with more progress and info if you please.
The formula for lateral chromatic aberration (LC) is
LC = P / b
where "P" the lens prism (decentration times power), "v" is the Abbe value of
the lens material. To minimize LC decrease the prism or increase the Abbe
value.
Welcome to s.m.v.
Robert Martellaro
~~~~~~~~~~~~~~~~~~
Optician/Owner
Roberts Optical
robopt@execpc.com
~~~~~~~~~~~~~~~~~~
"An expert is a person who has made all the mistakes that can be made in a very narrow field."
- Niels Bohr