What is the difference between inner progressives and outer progressives?

What are inner progressives and outer progressives?

 

Outer Progressives

The outer progressive lens is also called the front surface design progressive lens, that is the power gradient area is placed on the front surface of the lens, farther away from the eyes.

 

Inner Progressives

Inner progressive is also known as back surface design progressive lens, this kind of progressive lens refers to the use of free form surface technology and lathe processing equipment to place the degree gradient design (functional surface) on the rear surface, relatively close to the eyes.

The manufacturing difference between inner progressive and outer progressive

Outer progressive lenses are manufactured using a combination of two processing methods.

2. Secondary processing

From the stock of lenses produced by the first processing, find out the UC lenses with the required ADD, and machine it on the back surface of the lens to achieve the distant power. After these two processing steps, a pair of progressive lenses is completed.