1.56 Semi Finished Round Top Bifocal Lens Blanks
Material: 1.56 Index NK55 Resin
(Ne=1.549, Abbe=38, Specific Gravity=1.28)
Segment Placement: 5mm down -5mm in
Add Power: +1.00 to +3.50 in 0.25D steps
Segment Size: 28mm
|CT/ET||Frong sag |
|RX Range |
Some time after age 40, you will begin to notice the symptoms of presbyopia, including that feeling that your arms "aren't long enough" to hold a newspaper or magazine at a position where you can read it clearly.
If you already wear prescription eyeglasses, this generally means you will need to begin wearing bifocal lenses, such as round top bifocals to continue to see clearly at all distances.
One Lens, Many Functions
Round-top bifocal eyeglass lenses contain two or more lens powers to help you see objects at all distances after you lose the ability to naturally change the focus of your eyes due to age (presbyopia).
Suitable not only elderly, but also children and young aldults
Though RT bifocal lenses usually are prescribed for adults over age 40 to compensate for presbyopia, in some cases bifocals are prescribed for children and young adults who have eye teaming or focusing problems that cause eye strain when reading. In these cases, the bottom portion of the bifocal lens reduces the amount of focusing effort required to see near objects clearly.