What are the markings on varifocal lenses?
Occasionally, progressive glasses may have marks on them, and some people believe that these marks are defects in the lenses. The marks may appear as circles, letters, or numbers.
What are these marks? Is it embarrassing to wear glasses with marks on them? No. These marks are the marks left behind during processing of the lenses. To align exactly where the point in the lens where your distance prescription changes into a reading prescription is engraved or etched, this is a standard industrial practice. The engravings are etched into the front surface of the lens at approximately 0.05 mm depth. As a comparison, human hair typically measures between 0.06 and 0.08 millimeters in thickness.
In each lens, you will find two of these circles (or other identifying marks depending on the manufacturer of the lens, but they are always the same in each lens). The 175 represents the reading power or the ADD according to your prescription.
These marks always appear in the blending regions of the lens, which contain non-prescribed power and provide only minimal visual utility. Consequently, these marks will not affect your vision. It will not matter whether you are able to see directly through the marks while wearing them, since the power you are looking through will not be.
How do you identify progressive markings?
A majority of modern lenses are marked with laser engravings (older lenses may have fluorescent markings). Look for the engraved symbols and refer to the Index at the front of the book to identify them.
If you examine the front of the lenses very closely with an incandescent light and a 7x magnifier, you may be able to see marks if they are present. On older lenses, the nasal mark may appear even if the temple or outer marks do not. Concentrate on those first.