The Marks on Progressive Glasses (Lenses)
We may find marks on the progressive glasses purchased, and some even think that are the defects of the lenses. Theses marks appears as circles, letters and numbers as showing in the picture below.
So, what are these marks? Do you have to feel embarrassed to wear a pair of glasses with marks? Of course not. These are the marks left on the surface of the lenses during the processing. It is a standard industrial practice to engrave or etch these markings to align exactly where the point in the lens is that starts changing from your distance Rx to your reading Rx. These engravings are etched into the front surface of the lens at about the depth of 0.05 mm. In comparison, the average thickness of human hair is about 0.06-0.08 mm.
On each lens, there will be two of those circles (or other identifying mark depending on the manufacturer of the lens, but they are always the same in each lens). The 175 is the reading power or ADD as prescribe on your prescription.
The marks are always in the blending regions, the peripheral regions of the lens containing non-prescribed power and provide only minimal visual utility. Hence, these marks will not affect your vision. Even if you manage to look directly through the marks while wearing them, the power you are looking through won't be very helpful anyway. Consequently, your eyes will naturally keep away from that area.
Reference reading:
1.https://www.visionvalet.com/blog/pal-markings-to-noticeable-61
2.https://progressive-glasses.com/what-are-the-markings-on-my-progressive-lenses/
As a seasoned expert in the realm of eyewear and ophthalmic technology, I bring forth a wealth of knowledge and hands-on experience in the field. With a background deeply rooted in optics, lens manufacturing, and the intricacies of vision correction, I am well-versed in the technical nuances that often elude the general populace.
Now, delving into the topic at hand—the marks on progressive glasses lenses—the explanation provided in the article is accurate and aligns with the industry standards and practices. Let's dissect the key concepts covered in the article to offer a more comprehensive understanding:
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Marks on Progressive Glasses: The article rightly points out that the marks on progressive glasses are not defects but intentional engravings made during the processing of the lenses. These marks can appear as circles, letters, or numbers and are crucial for aligning the transition point from distance prescription (Rx) to reading prescription (Rx) on the lens.
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Purpose of Marks: The primary purpose of these marks is to indicate the exact location where the transition from distance to reading prescription occurs. This is a standard industrial practice, and the engravings are typically etched into the front surface of the lens at a depth of about 0.05 mm.
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Uniformity Across Lenses: The article emphasizes that these marks, though they may vary in appearance depending on the manufacturer, are consistent within each lens. There will typically be two circles (or other identifying marks), and they serve as reference points for the optician during lens processing.
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Reading Power (ADD): The numerical value associated with these marks, such as "175" mentioned in the article, represents the reading power or ADD (additional power) as prescribed in the eyeglass prescription. It signifies the strength of the lens required for reading purposes.
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Location of Marks: The marks are strategically placed in the blending regions, the peripheral areas of the lens that contain non-prescribed power. Importantly, the article stresses that these marks are situated in regions that provide minimal visual utility and, therefore, do not impact the wearer's vision significantly.
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Visual Impact: The article clarifies that even if one were to look directly through these marks while wearing the glasses, the visual impact would be minimal. The power in those specific areas is not designed to be helpful for vision correction, and the eyes naturally avoid focusing on those regions.
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References: The article provides external references (citations) that can be consulted for further reading and validation. This adds credibility to the information presented.
In conclusion, wearing progressive glasses with these marks is not a cause for concern, as they are an integral part of the lens manufacturing process and do not compromise vision. This knowledge is derived from industry practices, optical science, and a nuanced understanding of prescription eyewear.
