The Analyzer does the Rx calculation according to the following rules:

1.Drop .25 D cylinder powers.  
For example, +4.00+0.25X90 becomes a +4.00 sphere.

2.For cylinder powers from .50 to 1.25, use the spherical equivalent.  
This would yield:

For +.50, add .25  to the sphere power
For +.75, add .37 to the sphere power
For +1.00, add .50 to the sphere power
For +1.25, add .62 to the sphere power

If minus cylinders are used, the number would be subtracted from the sphere power.  
For example,  +1.00-1.00X90 becomes a +0.50 sphere. The full cylinder correction 
is used for cylinder powers 1.50 D and above.

3. A correction for the distance from the eye to the bowl, 
calculated according to the patient's age, is then added to 
the sphere power of the distance correction, as follows:

Under age 30, no add
Age 30 to 39, add +1.00
Age 40 to 44, add +1.50
Age 45 to 49, add +2.00
Age 50 to 54, add +2.50
Age 55 to 59, add +3.00
Age 60 and up, add +3.25

Example:  For a 40 year old,  +1.00+1.50X90 becomes +2.50+1.50X90.

An example from start to finish would be as follows:  
The patient is 50 years old and has a distance correction of -2.00+0.75X90.  
Since the cylinder power is between .50 and 1.25, we add the spherical equivalent 
of the cylinder power (+0.37) to the sphere power (-2.00) and we get -1.63.  
You can round off to -1.50 if you like.  Our patient is 50 years old, so +2.50 
is added to -1.50 to get +1.00.  A +1.00 D lens is placed in the lens holder.