If you're a glasses wearer you may notice some numbers on the arms or the bridge. These numbers usually include the frame model, colour code and measurements. This may look something like the following image:
The numbers displayed in this image indicate the following dimensions:
The bridge width is the minimum horizontal distance between the nasal surfaces of the rims on a plastic or metal frame, or the minimum horizontal distance between the nasal surfaces of the lenses in rimless frames. If a frame has adjustable nose pads on metal arms various modifications can be made in order to achieve a satisfactory fit.
Increasing the distance between the pads may be appropriate in cases when:
- The frame size is sitting too high on the face
- The bifocal segments or distance section of a progressive (Varifocal) lens are too high
- The bridge is too small a fitting for the nose
- The distance from the eye to the lens is too great.
Decreasing the distance between the pads may be appropriate in cases when
- The frame sits too low on the face.
- The bifocal segments or distance section of a progressive (Varifocal) lens are too low for the nos.
- The lenses are sitting too close to the eyes and lashe.
The Lens Width
The lens width is the distance between the vertical sides of a rectangle containing the lens shape (in mm), the diagram above illustrates this. The sizes for the lens width and bridge width can usually be found on your current glasses by looking on the inside of the frame (usually printed on the arms or the bridge)
The Arm Length
The arm length is measured from the dowel point to the extreme end of the side, this is made up of the length to the bend and the length of the drop to give the overall length of side. When choosing a new spectacle frame check your current frame sizes by looking for the printed measurements (usually found on the arm or bridge), for example:
52 (mm) will represent the lens width
16(mm) will represent the bridge width
52 (mm) will represent the overall length of the arm
Another measurement to consider would be the overall width of the frames, the diagram above illustrates this, it is important to note, aside from two times the lens width plus the bridge width the overall width is also dictated by factors such as the thickness of the rims of the frames and how swept out the lugs are from the frame. Our measurements give an approximate indication to the overall width taking into consideration the lenses and bridge not the lugs of the frame, this measurement is approximate and will vary according to the type and design of the frames.
It was really helpful for seamless online purchases of frames.Apr 23, 2017