To ensure perfect vision, optical lenses must be correctly placed in front of the each pupil, whatever the type of prescription.
To properly make an optical equipment, it is necessary to measure 4 data:
- The ½ pupillary distance of the left eye and the right eye.
- The heights between the pupils and the bottom of each lens, left and right.
While the ½ pupillary distance is an individual-specific figure (anatomy of the face), the two heights are dependent on both the individual and the frame that is chosen.
The vast majority of online opticians are satisfied with approximations when it comes to heights on sunglasses