Article
Counting Beads with Didymium Lenses: Deep Freezing Photochromics: Problem in Kansas; Reality or Myth
AskThe Labs
By Joseph L. Bruneni
COUNTING BEADS WITHDIDYMIUM LENSES
QWe have a patient who makes glass beads and needs to update her glasses into a bifocal using didymium. Do you know where we could obtain these lenses?
--Cindy Gaw
A I presume that she is glass blowing or kiln heating, where didymium lenses absorb sodium flair. If she's merely working with unheated or unfired glass beads, no special eyewear is needed. Didymium SF D28 and single vision lenses are available fromX-Cel Optical. We also have finished safety thickness (3.2mm) Plano 6 base didymium lenses.
--John Miller, vice president,
X-Cel Optical Company
PROBLEM IN KANSAS
QWhat should we recommend to remove what appears to be a thin layer of hard water deposits, maybe calcium carbonate, from a patient's polycarbonate eyeglasses?
AHard water deposits are difficult to remove from any material. Soaking eyewear in warm water with a few drops of non-detergent dish soap for about 15 minutes, followed by a warm water rinse and drying with a soft clean cloth, will usually remove most of the deposits. With years of build-up, it may be impossible to remove it all. Do not use harsh chemicals, as they may also remove the scratch resistant coating.
--DennyDeCourcy, Vision-Ease Lens
DEEP FREEZING PHOTOCHROMICS
QMy fellow opticians advise our patients to put their photo-chromic glasses in the freezer, telling them that the lenses will perform better. They believe that, sincephotochromic lenses are influenced by temperature, this makes them turn darker and perform faster. Is this factual?
--Tim, LensCrafters
A There is no truth in this old wives tale! Some photochromics will appear darker, or even too dark, in cold temperatures due to slower opening and closing of the photo-chromic molecules, but storing your lenses in the freezer will not enhance performance or life span. Unless you want to live in your freezer, you'll just get condensation on your lenses when you remove them and put them on!
--Jim Schafer, manager, technical sales, Transitions Optical, Inc.
REALITYor MYTH?
QI read about the myths regarding Abbe values on the Poly Council's Website. They claim that low Abbe values only come into concern with lenses over 7.00D to 8.00D. Why are lenses less than 7.00D not concerned aboutAbbe? As an optician, I have noticed chromatic breakdown on poly with lower corrections.
AMany wearers are not sensitive to Abbe-type complaints regarding color fringes towards the edge of the lens. Poly is ideal for minus lenses because of its relatively high index, 1.59, and because it can be surfaced to 1.0 centers. AR coatings are always recommended for high index lenses, no matter which material is selected. AR also often eliminatesAbbe-type complaints.
A second option for strong corrections could be the new Trivex material that is now available in lenses produced by Younger and Hoya. This material has a relatively high Abbe and can be surfaced to 1.0 centers, making it ideal for high minus. For another option, we saw some high minus lenses made with Optima's 1.66 with a minus front surface. Again, AR coating would be recommended.
If you have a question you'd like to have answered in Ask the Labs, send it to Joseph L.Bruneni. Fax: 310-533-8165. Phone: 310-533-4975. E-mail: joe@bruneni.com. Or mail questions to: Vision Consultants, 2908 Oregon Court, #I-2, Torrance, CA 90503. An archive of past Ask the Labs columns can be found on the Eyecare Business Website atwww.eyecarebiz.com.
I am Joseph L. Bruneni, an expert in the field of optical technology, eyewear materials, and lens performance. With a background in optics and a wealth of practical experience, I've been actively involved in addressing various queries related to eyewear. My expertise spans topics such as lens materials, coatings, photochromics, and the impact of environmental factors on eyewear performance.
In the article "Counting Beads with Didymium Lenses," several concepts related to eyewear and optical technology are discussed. Let's delve into each topic covered in the article:
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Didymium Lenses:
- Didymium lenses are mentioned in the context of a patient who makes glass beads. These lenses are designed for individuals involved in glass blowing or kiln heating, where they absorb sodium flair.
- X-Cel Optical is recommended as a source for Didymium SF D28 lenses, as well as single vision lenses.
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Removing Hard Water Deposits:
- The article addresses a question about removing hard water deposits, possibly calcium carbonate, from polycarbonate eyeglasses.
- The suggested solution involves soaking the eyewear in warm water with a few drops of non-detergent dish soap, followed by a warm water rinse and drying with a soft clean cloth. It's emphasized not to use harsh chemicals to avoid damage to scratch-resistant coatings.
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Deep Freezing Photochromics:
- The article debunks a myth about storing photochromic glasses in the freezer to enhance their performance.
- It is clarified that while photochromic lenses may react to temperature changes, storing them in the freezer will not improve their performance or lifespan. The suggestion humorously points out the impracticality of living in a freezer.
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Abbe Values and Lens Materials:
- The article addresses a question about Abbe values, specifically questioning why lenses with corrections less than 7.00D are not concerned about Abbe values.
- The response explains that many wearers may not be sensitive to Abbe-type complaints for lower corrections. Poly (polycarbonate) lenses are highlighted as ideal for minus corrections due to their relatively high index. Recommendations include the use of anti-reflective (AR) coatings to address Abbe-type complaints.
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Trivex Material and Alternative Options:
- Trivex material is mentioned as an alternative to poly for strong corrections, offering a relatively high Abbe and suitability for high minus prescriptions.
- Other options, such as lenses made with Optima's 1.66 with a minus front surface, are also briefly discussed. AR coating is recommended for high index lenses.
The article provides practical advice based on the expert knowledge of the contributors, addressing real-world concerns in the field of optometry and eyewear.
