Prescription Numbers - Meaning?

[MM]

What do the numbers on a corrective lens prescription mean?

Mine has columns for Sph, Cyl, and Axis:

Sph Cyl Axis
O.D. -11.25 +3.00 92
O.S. -12.00 +3.00 77

Yes, I'm pretty myopic, but what do Cyl (cylinder, I assume) and Axis mean?
Something to do with astigmatism, I assume. I know that -11 and -12 indicate
severe myopia but what magnitude of astigmatism do the other numbers indicate?
Also, what is Prism and Base?

Inquiring minds want to know....

Thanks

Mark

[Anthony G Podloski]

In article <7h5amn$422$3...@nnrp03.primenet.com>,
mar...@primenet.com (MM) wrote:

>Mine has columns for Sph, Cyl, and Axis:
>
> Sph Cyl Axis
>O.D. -11.25 +3.00 92
>O.S. -12.00 +3.00 77
>
>Yes, I'm pretty myopic, but what do Cyl (cylinder, I assume) and Axis mean?

An astigmatic cornea has two different powers in two different
meridians. The sphere number is the refractive error of the cornea in the
axis meridian (92 and 77 in your example). The cylinder number can be added
to the sphere power to give the power in the other meridian (usually 90
degrees away).

>Also, what is Prism and Base?

Prism is used to bend light towards the direction of the base. The base
is the thicker portion of the prism (with the "apex" being the thin end).

----

Anthony Podloski <podl...@ix.netcom.com>
Third Year Intern, SUNY College of Optometry
NYSOA Student Society President
APHA Liaison
Seventh Floor Committee Chairman

http://www.geocities.com/MotorCity/1400/ My Virtual Home

[DLM67213]

mark,
Your RX is written in a rather obsolete form.Usually the cyl power is written
in a minus form. After transposing your RX it should read

-8,25 -3.00 092 -9.00 -3.00 077
Simply stated the Cyl number shows the power of the correction of your
astigmatism (which just means that your eye is not perfectly
round). The 77 means that the axis is at 77degrees.You do have a pretty good
degree of astigmatism. If you have a prism on your RX that means you probably
have a muscle weakness that needs to be corrected. Prism helps people that have
double vision or eyes that do not "track" together.The base is telling the
optical lab whether the base of the prism is up down, in or out. I know this is
vague but I could dd this so much better if I could draw you a picture. That is
how I learned!!!!

[Michael and Dawn Messer]

> Your RX is written in a rather obsolete form.Usually the cyl power is
written
> in a minus form. After transposing your RX it should read
>
> -8,25 -3.00 092 -9.00 -3.00 077

Don't forget to change the axis 90 degrees when you transpose into minus
cylinder form, (i.e.: 002 and 167).