B - DESIGN TUTORIAL
Refract patient (convert to minus cylinder if necessary).
Obtain Keratometry readings.
Select B - Design trial lens closest to flat "K."
Adjust base curve of lens to be ordered.
Final RGP Rx should be the sphere power (adjusted for vertex) of patient's spectacle Rx.
"K" 43.25 / 44.00
Rx -2.00 -1.00 x 180
Trial B - Design 43.50
Over Refraction -2.25
Final Lens Rx 43.25 -2.00 9.0
Using the B – Design system you can see that this patient had an over-refraction of -0.25 stronger than their spectacle Rx caused by a tear lens of +0.25 so you would flatten the base curve and keep the Rx the same as their spectacle Rx.
Minus over-refraction = flatter base curve
Plus over-refraction = steeper base curve