Who Needs 1.74 Lenses?
- It's not prescription alone decides whether one needs to use 1.74 lens.
- The combination of prescription, pupillary distances, the frame to be used will decide whether 1.74 high index lenses should be used.
- Our unique software driven lens recommendation helps you selecting your lenses without visiting a local store.
1.74 vs. 1.67
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1.74 high index lenses are thinner and lighter than 1.67 high index lenses.
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1.67 high index lenses are much less costly compared to 1.74.
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1.67 high index is available in many products: color tinted, photochromic (light-responsive), blue stoppers, photochromic blue stoppers and polarized.
Our 1.74 High Index Lenses
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1.74 High-Index Anti-Reflective Lenses: $63.95 $31.95
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1.74 High-Index Digital Free Form Anti-Reflective Lenses: $79.95
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1.74 Digital Free Form Progressive (No-line multi-focal) Lenses: $86.95
How To Order
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- Enter/Confirm Your Prescription
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- Select LIGHT-RESPONSIVE as Your Lens Type
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- Pick Photochromic Blue Stoppers From Our Recommendations or Customized List
FAQ
Common indexes of ophthalmic plastics:
1.50 (CR-39 plastic), 1.56, 1.59 (Polycarbonate), 1.61, 1.67 & 1.74
What about weight?
With few exceptions, the higher index materials weigh more than lower indexes. 1.74 weighs the most with a specific gravity of 1.47 - However, since less lens material is needed to achieve the desired outcome, the overall weight of the lens is less compared to other materials with the same refractive power (Refractive power is called Diopters)
Do they have UV protection?
High index lenses, compared to CR-39 also block 100% UVA & UVB. With no exceptions, higher index plastics have higher rate of reflectance. As a comparison, CR-39 Plastic reflects 7.7% of all light. 1.74 reflects 13.6% of all light. Because of this, higher index lenses should have Anti-reflective (A/R) coatings. 1.74 is the only lens that automatically includes A/R, giving it ~ 0.5% reflectance.
Other considerations?
Higher index lenses, because they refract better, do not need to be as round. The front surface can be more flat than lower index lenses. This allows them to better fit in frames which are typically more flat on the front surface
Flatter front surfaces also reduce "Spherical Aberrations". This is "variation in focal length of a lens or mirror from center to edge, due to its spherical shape." Basically spherical aberration means that the farther from the center of the lens, the more imperfect refraction. Flatter lenses have less spherical aberration.
1.74 is also have great tensile strength, so lenses that need to be drilled, don't fracture as much as lower index lenses (except polycarbonate which is also great for drilled lenses).
Most of these properties apply to all higher index lenses, with 1.74 being the most advanced, highest index plastic lens, therefore these good properties are best in 1.74 material.
1.74 = thinnest, lightest lens with least amount of spherical aberration. 100% UV blocking and A/R included.