Glasses have three primary sizes you need to know about: lens, bridge and temple.
A) EYE SIZE
is the width of the lenses at the widest part.
B) BRIDGE SIZE
measures the piece of metal or plastic that connects the lenses, in order to measure the bridge, you have to start and end at the innermost side of the lenses and measure to the same spot on the other side of the bridge.
C) TEMPLE SIZE
is the measurement of the arms of the sunglasses, the size of the arms starts at the hinges and continues in a straight line to the farthest point without sloping downward.