This info was great! I also confirmed with:
https://www.thevisioncouncil.org/sites/default/files/TVC-Lens-Description-Standard-2-1-Final.pdf
What I found, and please verify if you’d be so kind!
The front radii of blanks are usually standard in the 6 diopter range, which equates to a radius of 337.5/6 = 56.25 mm, and based on my lenses which roughly have a 100mm radius on the outside, 337.5/100mm = a diopter of about 3.4.
With this info my right eye prescription is: SPH -2.25, CYL -0.5, ANG 127
SO, using this equation I found in the literature where Ft = Total lens power, Ff = Front power, Fb = Back power, n = refractive index 1.5403 for clear resin, and t = thickness at minimum in meters 0.0027m
Ft = Ff / ( 1 - ( t * Ff / n ) + Fb
-2.25 = 3.4 / ( 1 - ( .0027 * 3.4 / 1.5403) + Fb
Fb = -5.67 diopters or 337.5/5.67 = 59.52mm radius
With the additional cylindrical part of my prescription to correct my astigmatism, I’m assuming that the total power along the 127 degree axis needs to be -2.75, giving me a radius of 54.70mm at 127 degree and the 59.52mm radius at (127-90) or 37 degree.
Thoughts?
