Dear Doug,
Subject: Calculation of "Spherical Equivalent" power
You take your listed "Spherical" and add 1/2 the
astigmatic number. (Ignore the degrees.)
Thus, for example, your right eye:
11.25 + ( 2.5 / 2 )
11.25 + (  1.25 )
Spherical equivalent = 12.5 diopters, right eye.
Enjoy,
Or
What's "spherical equivalent refraction"? My right eye
prescription is 11.25 2.50x178 I believe this means that my lens
has a power of 11.25D at 178 degrees, and 13.75D at 88 degrees,
and I heard of this term "spherical equivalent refraction", which
On May 1, 1:39*am, douglas <(EMail Removed)> wrote:
> On Apr 30, 10:37*pm, Salmon Egg <(EMail Removed)> wrote:
>
>
>
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> > In article
> > <(EMail Removed)>,
>
> > *douglas <(EMail Removed)> wrote:
> > > What's "spherical equivalent refraction"? My right eye
> > > prescription is 11.25 2.50x178 I believe this means that my lens
> > > has a power of 11.25D at 178 degrees, and 13.75D at 88 degrees,
> > > and I heard of this term "spherical equivalent refraction", which
> > > apparently is calculated by adding the spherical power, and
> > > cylinderical power divided by 2, so this means I've got an SER of
> > > 12.50D. What's the purpose of calculating the SER, how can it help my
> > > ophthalmologist and optometrist?
>
> > > Thanks!
>
> > This is one subject I get up on a soap box about.
>
> > The way prescriptions are given in terms of adding together spherical
> > power and cylindrical power. Unfortunately, this combination is not
> > unique and IIRC, optometrists and ophthalmologists have traditionally
> > not used the same convention to describe a prescription. If Zernike
> > functions were used instead, there would be a unique combination of one
> > spherical and two astigmatism functions. However, because cylindrical
> > lenses are easier to understand and manufacture, I do not expect Zernike
> > functions to take over soon.
>
> > Bill
>
> Um, okayyyy...you didn't really answer my question. And what are
> Zernike functions? How would my prescription be written using them? Hide quoted text 
>
>  Show quoted text 
