How much clearance, in millimeters, should there be between the nose and the free side of the bridge when checking bridge size?

When checking bridge size in eyewear fitting, a clearance of 1.0 millimeters between the nose and the free side of the bridge is ideal for ensuring comfort and proper fit. This space allows for the natural contours of the nose without applying excessive pressure, which can lead to discomfort or irritation during wear.

A clearance of this measurement ensures that the frames sit securely on the nose while still allowing for slight movement without pinching. It also promotes stability of the eyewear on the face, helping to prevent slippage. Clearances that are too small may lead to pressure points, while those that are excessively large may cause the glasses to slide down the nose, leading to visual obstruction and an overall poor fit. Thus, the specified 1.0mm clearance strikes an effective balance for achieving proper bridge fit.