Working Distance: that is the distance between your eyes and the operation area. To measure your working distance, place yourself as you will be using the loupes, whether sitting or standing, and measure the distance between your eyes and the work area or the patient .
Pupil Distance: If you choose to buy TTL loupes, We also need your Near PD which is the distance between your pupils while looking at close objects. You can go to any optical store to get it measured. Be sure to let the optician know you need Reading PD.