Before revision: The power could be read right off the dial without having to do mental calculations, the range was far higher, from +19.75 to -28.00 and with cylinders up to ± 7.50, the battery of cylinders was much more intuitive and easy to use, and it was the first to have Jackson cross cylinders affixed, (the first AO Phoroptors with JCC's were late models of the Additive, and very late Genothalmic Refractors also had them).
After revision: The power could be read right off the dial without having to do mental calculations, the range was far higher, from +19.75 to -28.00 and with cylinders up to 7.50, the battery of cylinders was much more intuitive and easy to use, and it was the first to have Jackson cross cylinders affixed, (the first AO Phoroptors with JCC's were late models of the Additive, and very late Genothalmic Refractors also had them).