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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 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
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:
52-16-135
52 (mm) will represent the lens width
16 (mm) will represent the bridge width
135 (mm) will represent the overall length of the arm
Overall Frame Width
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.
Melanin in Lenses Explained
Melanin is natural pigment found throughout the human body. Its purpose is to protect us against sunlight damage by filtering Ultraviolet (UV) and High Energy Visible (HEV) light, better known as "Violet-Blue light". Melanin provides one of the best natural defences against the harmful effects of the sun.
Why include melanin in lenses?
Most lenses will filter out UV light and reduce a certain amount of visible light entering the eye. However, when synthetic melanin is infused into the lens it will provide the ultimate eye protection by filtering out up to 98% of the HEV light. It is the equivalent to a sun lotion with a SPF (Sun Protection Factor) superior to 140. In effect it reduces long-term exposure to the retina and could make up for the loss of retinal melanin which occurs with increasing age. This will help to reduce the probable damage that contributes to age-related macular degeneration (AMD) and cataracts.
An additional benefit is clearer vision. This is due to the high energy associated with blue light, which is scattered more than other wavelengths because it attaches to moisture in the air resulting in haze. Melanin lenses, by filtering most of HEV light, eliminate this associated haze effect, allowing for enhanced contrast, true colour & sharper images.
Overall, melanin in lenses provides higher protection and better performance at the same time!