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Eyeglass bridge spread is the horizontal distance between the two lenses, measured at the narrowest point of the frame bridge. This measurement is important because it determines how the frame rests on the nose and affects the fit of the nose pads.
read more about eyeglass bridge spread ...The correct bridge spread is important for comfort. If the spread is too narrow, the frame will sit too high and pinch the nose. If the spread is too wide, the frames will slide down the nose easily and sit too low, resting on the cheeks.
Bridge spread is measured in millimeters and is one of the three numbers typically stamped on the inside of the frame arm (e.g., 50-18-140, where 18 is the bridge spread). This measurement is standardized across the eyewear industry.
Bridge spread is a property of the frame itself (the distance between the two lenses). PD (Pupillary Distance) is a property of the wearer (the distance between the pupils). Both measurements must be compatible for a comfortable fit.
The correct bridge spread makes sure your backup frames are stable and correctly centered. This stable fit helps provide steady, comfortable vision correction immediately when you switch from your contact lenses.
On plastic frames, the bridge spread is fixed. On metal frames, an optician can adjust the nose pad arms to change the effective spread.
The average bridge spread measurement is typically between 14 mm and 24 mm.
No, the bridge spread needs to be compatible with your nose size, while the PD dictates the position of the optical center.
If your glasses sit too high on your nose, the bridge spread is likely too narrow. This can "cut" the bottom of your field of view. On metal frames, an optician can widen the pads; on plastic, you may need a different "bridge size" entirely to avoid vision disruption.
All About Vision. Understanding Frame Measurements (allaboutvision.com). 2024.
ABDO. Ophthalmic Frame Measurements (abdo.org.uk). 2023.
The Vision Council. Selecting the Right Frame (thevisioncouncil.org). 2024.
Review of Optometry. Troubleshooting Progressive Failures (reviewofoptometry.com). 2024.