lenses Guide

Lens Index and Quality Guide

While choosing eyeglasses, people often focus on frames for style and comfort, but the quality of lenses matters too. High-performing lenses enhance both comfort and vision. The term "lens index" (or refractive index) is essential, influencing lens thickness and effectiveness in correcting vision.

What is Lens Index?

The index number of a lens is a crucial determinant of its thickness or thinness and its ability to bend light effectively. A higher index indicates a thinner lens, as it bends light more efficiently. Therefore, for stronger prescriptions, higher-index lenses are often preferred for their thinness, lightness, and comfort. Typically, index numbers range from 1.50 to 1.74, with 1.74 being the thinnest lens available

Clear Understanding of Different Lens Indexes

All-inclusive frames typically use CR 39 plastic lenses with an index of 1.5. Standard lenses are thicker but more affordable, suitable for low prescriptions. High-index lenses are recommended for stronger prescriptions, offering comfort, aesthetic appeal, and superior vision due to their better light-bending ability.

AVAILABLE INDEX LENSES

1.5 Index Lens – Standard/Regular Lenses

For prescriptions with spherical (SPH) values of -2.5, +2.5, and below, it's advisable to opt for the thickest lenses available. To minimize the risk of lens cracking, selecting full-rimmed frames is recommended. These lenses are typically made of CR-39, a type of conventional plastic known for its durability and reliability.

1.53 Index Lens – Mid Index Thin and Light Lenses

Introducing our 1.53 index lenses, 15% thinner than standard 1.5 index. Perfect for SPH +2.00, -2.75 prescriptions, they offer superior optics and a lightweight design.

1.57 Index Lens – Polycarbonate Lenses

Polycarbonate lenses, originally designed for safety glasses, have expanded their application to include kids' glasses, sports eyewear, and a wide range of prescription lenses. Offering both optical clarity and 100% UV protection, the 1.57 index polycarbonate lenses are versatile and suitable for various needs. Additionally, they can be seamlessly fitted into rimless glasses, providing both aesthetic appeal and functionality.

1.61 High-index Lens – Super-thin Lenses

The high-index lenses start from this value. They offer a remarkable slimness, nearly 20% thinner than those with a 1.5 index. These lenses are particularly suited for individuals with stronger prescriptions, typically ranging between +3.00 to -3.00 and above, up to +6.00 to -6.00. They feature thinner edges and reduced overall weight, making them a preferred choice. Full rim or semi-rim frames are recommended for optimal support and aesthetic appeal. The high-index lenses start from this value. They offer a remarkable slimness, nearly 20% thinner than those with a 1.5 index. These lenses are particularly suited for individuals with stronger prescriptions, typically ranging between +3.00 to -3.00 and above, up to +6.00 to -6.00. They feature thinner edges and reduced overall weight, making them a preferred choice. Full rim or semi-rim frames are recommended for optimal support and aesthetic appeal.

1.67 High-index Lens – Ultra-thin Lenses:

These ultra-thin 1.67 index lenses outperform polycarbonate lenses by being 20% thinner and traditional lenses by 30%. They're particularly suitable for higher prescriptions, including SPH corrections ranging from +6.25 to +8.00 and -6.25 to -8.00, as well as CYL corrections of +3.25, -3.25, and +4.00, -4.00. Their reduced weight and thickness make them the optimal choice for enhanced comfort and aesthetics. Above 1.67 High-Index, we offer lenses such as 1.74, 1.80, and 1.90, among others. However, these options are available only by special order, typically upon request from a doctor, and thus we do not provide general descriptions for them.

MATERIAL OF THE LENSES

Classic Material: Plastic Lens

Plastic or CR39 lenses offer remarkable clarity comparable to glass, making them a cost-effective choice, especially for tinting purposes. However, they tend to be thicker and heavier compared to Polycarbonate ("Poly") lenses. Despite their clarity, plastic lenses are susceptible to scratching, cracking, or shattering. Additionally, they are not compatible with drill-mounted or semi-rimless frames. Due to safety concerns, plastic lenses are not recommended for children under the age of 18.

ADVANTAGES OF PLASTIC LENS MATERIAL:
  • Great for people on a budget. Plastic lenses tend to be less expensive.
  • Great material for smaller prescriptions. Prescriptions up to +/- 2.50.
  • Holds tint well. Ideal for hand-dipped tinting to make a sunglass if you do not want to have a polarized sunglass lens. Best material for darker tint color.
  • Plastic clarity is as close to glass as it can get without being glass.
  • Can be used for inexpensive backup glasses to have on hand, or that pair of blue light glasses you only use at the computer.
DISADVANTAGES OF PLASTIC LENS MATERIAL:
  • Plastic is a softer material and brittle. Not recommended for wearing if you are active. Easier to scratch.
  • Lenses tend to be thicker.
  • Not recommended for children under the age of 18.
  • Can’t be used for drill mount or wrap frames.

Most Common Material: Polycarbonate Lenses

Polycarbonate material gained prominence in 1962 as the transparent shield for astronauts' "bubble helmets," prized for its clarity and durability. By the 1980s, it proved ideal for optical lenses, outshining glass and plastic alternatives in durability. Its impact resistance made it the go-to choice for children's lenses. Today, polycarbonate reigns as the preferred material across industries for its unmatched clarity, strength, and resilience, making it the top choice for diverse applications.

ADVANTAGES OF POLYCARBONATE LENS MATERIAL:
  • Durability! If you have an active lifestyle, play sports, are prone to dropping or scratching your glasses these might work well for you. Much safer than glass or plastic. Highly impact resistant.
  • Good for children under 18 years of age.
  • Tend to be thinner and weigh less than a plastic or glass material.
  • Can be used for drill mount, semi-rimless or wrap frames.
  • Comes with built in UV protection.
DISADVANTAGES OF POLYCARBONATE LENS MATERIAL:
  • Lower clarity than glass or plastic.
  • More expensive than glass or plastic lens.
  • Will not absorb tint as dark as plastic.

High Index Replacement Lenses

High Index lenses, introduced in 1990, offer thinner and more attractive options for individuals with higher prescriptions, bending light more efficiently than regular lenses. If your prescription starts at +/- 3.00, consider High Index lenses (1.67 index for +/-3.00 to +/-6.00, 1.74 for +/-6.25 and above). These lenses combat the thick, heavy appearance associated with strong prescriptions. However, for prescriptions below +/-3.00, High Index lenses offer no noticeable advantage over standard lenses. Frame choice becomes crucial, with smaller frames resulting in thinner lenses. Full plastic frames are recommended for a sleek look and to hide protrusions. Ultimately, finding the right balance between lifestyle and vision needs is key when choosing lens materials.

ADVANTAGES OF HIGH INDEX LENS MATERIAL:
  • Thinner lens that fit better in your frame. Helps eliminate the edges that can protrude once you are in a higher prescription range.
  • They can be lighter than regular lens.
DISADVANTAGES OF POLYCARBONATE LENS MATERIAL:
  • They typically cost more than a regular lens. The increase in cost is due to the work product require more precise craftmanship. Lens can break easily during the creation process and jobs must start over.
  • They are brittle and people who are prone to drop or are hard on glasses may find themselves replacing them frequently.
  • They are very reflective and that is why they come with anti-reflective coating.
  • They are a softer material and can scratch easily.
  • As your eyes moves away from the optical center of the lens toward the edges, you may experience halos or chromic aberrations when you are in bright light.activities.

Glass Lens

Are glass lenses for you?

There's much debate surrounding the origins of the first optical lens, yet it's widely acknowledged that glass was the inaugural material to achieve global recognition. Despite their widespread popularity, glass lenses grappled with issues such as weightiness and susceptibility to shattering upon impact. Nonetheless, they maintained a sizable following.

The prominence of glass lenses diminished with the advent of CR-39 or plastic lenses during the 1960s, offering reduced weight without compromising clarity to a significant extent.

BENEFITS OF GLASS LENSES
  • The clarity of a glass lens still is the best there is available. The clarity you get on glass cannot be matched when next to plastic or polycarbonate. Clarity on glass is supreme! 
  • Glass can be ground to a 1.80 index in some vision types meaning that we can get the lens very thin for strong prescriptions.
  • Is almost scratch proof. Glass is very difficult to scratch through normal wear and tear.
  • Because it is nearly scratchproof and the clarity remains strong over time, there is less need to replace these as frequently as plastic or polycarbonate lenses – if you can keep them from shattering.

In Conclusion

As with all lenses there are pros and cons associated with each choice, and each individual needs to consider which will work best for their lifestyle and budget.

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