Tuesday, December 27, 2011

3 Prescriptions in 3 Weeks! Not Sure What to Choose?

Lindsey asks:
"Hi there. My 7 year old daughter went in for her 1st yearly eye exam (teacher's request due to issues seeing the board). We took 3 opinions and got 3 different prescriptions within a 3 week period. Script #1 is from a regular O.D and written in (-) form and Script #2 & #3 are from a Pediatric Eye Specialist M.D written in (+) form. 

I would like to know how I can convert Script #1 from a (-) form to a (+) form for proper comparison to decide how different it is from #2 & #3. Which prescription do you think we should use? Is it better to start a child out with the smaller precription first to get the eyes adjusted versus putting them in a higher power glasses and give a shock to the eyes?

1st script -1.00(SPH) -1.25(CYL) 005 (AXIS)
2nd script: -2.25(SPH) +1.00(CYL) 100 (AXIS)
3rd script: -2.50(SPH) +0.75(CYL) 90(AXIS)

1st Script: -1.00 (SPH) -1.25(CYL) 170(AXIS)
2nd Script: -2.75(SPH) +1.00(CYL) 80 (AXIS)
3rd Script: -2.50(SPH) +0.75(CYL) 90(AXIS)"

A: Lindsey,
Thanks for your question.  As a parent, I understand your desire to get the right prescription (RX) for your daughter.  I see from your daughter's Rx that she has myopia (nearsightedness) which makes things far away look blurry, and astigmatism (which means the power of her lenses up and down is different than it is side to side).  
When we write prescriptions for glasses, we can use the (+0) form to describe the cylinder correction for astigmatism or the minus (-)form.  Most glasses (except for some progressive addition multifocals) have the correction for the astigmatism (called cylinder) on the back surface of the lens because patients see a little better with it on the back verses the front.  No matter how the Rx is written, the lenses for your daughter will be made with the cyl on the back. Most OD's write in minus cyl form and most MD's write in plus form because that is the way they are taught.  

To convert between the two, add the sphere power to the cylinder power to get the sphere power of the other form, then switch the cylinder sign to the opposite sign, and add 90 to the axis power (axis is the angle that the cylinder sets at).   To convert your daughters 2nd script from plus to minus cyl form on her right eye, add -2.25 to +1.00= -1.25.  Change the sign on the cyl to (-) and add 90 to the axis. We express axis in degrees between zero and 180 degrees, so the axis 190 can also be expressed as axis 10. So her 2nd script in minus form would be -1.25-1.00 x 10 for her right eye and -1.75 -1.00 x 170 for her left eye.   

I would use the 1st script and see if she can see the board clearly, then I would have her checked again in 6 months and get stronger lenses only if needed.  

Thanks for your question.
Dr. Felker