When fitting the spectacle frame, the bridge is perhaps the most important part to consider when choosing your frames. It is the bridge that has the major bearing surface and area of contact between the front of the glasses and the face.
The bridge design should allow a comfortable and supportive fit which will maintain the position of the lenses over your eyes, allowing a natural gaze.
The Bridge Width
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 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
· The bridge is too low for the nose
· The lenses are sitting too close to the eyes and lashes
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:
(mm) will represent the lens width
(mm) will represent the bridge width
(mm) will represent the overall length of the arm
Below is how we would measure the arm length
Overall Frame Width
Another measurement to consider would be the overall width of the frames, the diagram above shows 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.
The Perfect Frame for you!