The numbers you find in the "Measure" field refer to numerical values (expressed in millimeters) that are useful in understanding the size and fit of your glasses. You can find this measurement inside the temples of your eyeglasses, usually right after the ID number. 

Taking the Measure as an example: 55/17/133


The first number (55) refers to the Calibre: a measurement of the horizontal diameter of the lens at its widest points. It is used to tell how large a lens is and what the effect of the eyeglass will be when worn. It is primarily an aesthetic parameter: a small diameter (e.g., 48-50) identifies eyeglasses with small lenses, suitable for small or women's faces; a larger diameter (e.g., 52-54-56), on the other hand, is more suitable for men's-cut glasses, large faces, or drop-lens glasses.


The second number (17) refers to the Bridge: distance between the lenses. It defines how the glasses will fit on the nasal septum, whether it will be comfortable, tight or perhaps too big. To figure out which value is best for you, take a soft centimeter and lay it on the spot on your nose where you usually wear your glasses, and measure the top of it (the contact surface of the glasses).


The third number (133) refers to the Temple: This parameter is important but not absolute, because in the case of somewhat short rods, one can work on the curvature of the rod to adjust the fit, or vice versa.