Measure pupillary distance scale is made of high quality PVC material, soft and elastic, not easy to break, can be used for a long time. Portable, flexible operation..The classic straight edge design is suitable for both eyes, the nose bridge design helps keep the PD ruler centered and fixed, and the eye pupil distance is the ruler to ensure accuracy..You just need to place the notch of the pupillometer as close to your eye as possible, then if your pupil is in the mirror, find the middle and read the line closest to the middle of the pupil..The marks on both sides of the pupil distance ruler can be used by both the left and right hands, which is convenient and comfortable. It can also be used to measure the eyeglass frame by oneself to change the lens.Optometrists, optometrists, eye doctors, and people who want to buying glasses online necessary convenient tools. Measure pupillary distance scale is cheap and practical..Optometrists, optometrists, eye doctors, and people who want to buying glasses online necessary convenient tools. Measure pupillary distance scale is cheap and practical.