Lens Options and Materials

Lens Materials

Posted by on May 5, 2010 in Lens Options and Materials | 5 comments

Refractive Index The refractive index of a lens material indicates how much the material will refract or bend light as it enters the material from air, by comparing the speed of light in a given material to the speed of light in air. The higher the index number of a given material, the more the light will refract as it enters the material. If a material has a greater ability to refract light, less of a curve is required to obtain a specific power, resulting in a thinner lens. Plastic (CR-39) and Crown Glass are considered base index with indices of 1.498 and 1.52 respectively. Materials with...

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Video: Lens Material Drop Tests

Posted by on May 5, 2010 in Lens Options and Materials | 0 comments

The following videos show the results of drop tests perfomed by Younger Optics on CR-39, Spectralite, 1.60, Polycarbonate, and Trivex. All tests were perfomed using a 500g missile with a 1 mm point. The lenses tested were all front-side coated with a center thickness of 2 mm. The CR-39, Spectralite, and 1.60 product were tested from a drop height of 50 inches, while the Poly and Trivex were tested from a drop height of 75 inches. CR-39 Drop Test Video Get the Flash Player to see this player. Spectralite Drop Test Video Get the Flash Player to see this player. 1.60 Drop Test Video Get...

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Basic Lens Styles

Posted by on May 4, 2010 in Lens Options and Materials | 0 comments

Single Vision Single vision lenses, as the name suggests, correct a single refractive error with a single focal length. When a myopic or hyperopic refractive error exists, spectacles are required to correct vision. Minus powered single vision lenses are used to correct myopia and plus powered single vision lenses are used to correct hyperopia. Single vision lenses can also be used as reading glasses for presbyopic patients who have clear distant vision, but require correction for close objects. Bifocals As people age, the lens of the eye tends to harden, resulting in a lessening of the...

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Trivex vs. Polycarbonate

Posted by on May 4, 2010 in Lens Options and Materials | 6 comments

Even though Trivex has been available for a while now, there is still much debate and confusion about how Trivex and polycarbonate stack up against one another. We’ll lay out the facts and attempt to put the question to rest. Polycarbonate Born from the space race in the 1960′s and introduced to the ophthalmic lens market in the late 1970′s, polycarbonate has been around the block a few times and enjoys a sizeable market share, particularly in children’s and safety eyewear due to its superior impact resistance. With a higher index of refraction and lower specific...

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Focus on Progressive Lenses

Posted by on May 4, 2010 in Lens Options and Materials | 0 comments

It Doesn't Last Forever Eventually it gets everyone. That point in a patient's life comes when no matter how perfect their vision may have been as a young adult, they begin to notice changes. The newspaper becomes more difficult to focus or the fine print on the restaurant menu isn't quite as sharp. They will have to face it, they are becoming a presbyope. When it comes time to visit their vision specialist, you will tell them that they require a variable focus form of correction because their prescription requirements for distance vision are divergent from those required for...

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Focus on Coatings

Posted by on May 4, 2010 in Lens Options and Materials | 2 comments

Lens Coatings – Advancing the Utility of Spectacle Lenses All optical materials, no matter how advanced or well-suited for a patient’s needs, suffer from innate shortcomings specific to the lenses chemical makeup. Where crown glass is unquestionably superior in optical quality, it is heavier and could shatter upon impact, thus it must be treated to resist such damage. Polycarbonate has long held the title on most impact resistant and is lighter in weight. Unfortunately, polycarbonate is not as resistant to scratching and therefore must be treated to improve its resilience to...

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