High-index lenses are made of special plastic material, making eyeglass lenses thinner and lighter. They have a higher refractive index than regular glass or plastic lenses, so they bend light more efficiently.
The refractive index measures how light bends when passing through a medium. High-index lenses bend light more efficiently than standard lenses, making them ideal for correcting strong prescriptions.
Generally, the higher your prescription, the higher the index you need. For reference, standard plastic lenses have a refractive index of 1.50. On the other hand, high-index lenses can have a refractive index of 1.53 to 1.74.
Why Do People Use High-Index Lenses?
Many people use high-index lenses because they look better and feel more comfortable than thicker lenses like the standard CR-39 plastic. CR-39 plastic is often considered standard, regular, or plastic lenses. They’re inexpensive and have excellent optical quality.
However, the lenses tend to be thick and can give you "bug-eyes'' with higher prescriptions. As such, people who require higher prescriptions may consider high-index lenses.
What Vision Problems Do High-Index Lenses Correct?
High-index plastic lenses correct all types of refractive errors, including:
- Myopia (nearsightedness)
- Hyperopia (farsightedness)
- Presbyopia (age-related farsightedness)
They are available as single-vision, bifocal, or progressive lenses.
Types of High-index Lenses
A lens index is a number that describes how thick or thin your lenses are. Thicker lenses often have a low index, and higher index lenses are typically thinner.
Here’s an overview of the different high-index lenses:
These lenses are about 25% thinner than CR-39 lenses. A 1.60 high-index lens is suitable for prescriptions around +3.00/-6.00 or less and astigmatism correction of -3.00 or less.
These lenses are about 30% thinner than CR-39 lenses. A 1.67 lens is suitable for prescriptions under +5.00/-8.00 and astigmatism correction between -3.00 and -4.00.
These lenses are at least 35% thinner than CR-39 lenses. They are the thinnest high-index lenses. This lens suits stronger prescriptions above +5.00/-8.00 and astigmatism correction between -4.00 and -6.00.
Pros and Cons of High-Index Lenses
While there are many benefits to wearing high-index lenses, you have to consider the following:
- Your prescription
- Type of frame you select
- Your eye sensitivity
Some people do better with certain lens materials than others.
Some benefits of high-index lenses include:
Lighter and Thinner
High-index lenses are lighter and thinner because they’re made of less material. This means you can wear these lenses for a long time without feeling uncomfortable.
Typically thicker lenses require bigger frames. So, having thinner lenses can give you more options when choosing frames.
Regular lenses don't offer UV protection. This lens treatment needs to be added separately.
Most high-index lenses already have 100% built-in UV protection. You don't have to worry about sun overexposure when wearing these lenses.
Crisp and Good Peripheral Vision
High-index lenses offer crisp and good peripheral vision when paired with an aspheric design. They're also good for stronger prescriptions because of their high refractive index.
Better Cosmetic Appeal
When wearing high-index lenses, eyes appear less magnified for farsighted prescriptions and less minified for nearsighted prescriptions. They minimize the "bug-eyes" look that comes with high-farsighted prescriptions. This offers a better cosmetic appeal than regular thick lenses.
Some drawbacks of high-index lenses include:
High-index lenses are more expensive to manufacture and more difficult to grind. They typically cost approximately $150 to $200 for single vision and $300 to $400 for progressives.
Less Lightweight or Impact-Resistant
Polycarbonate lenses or Trivex are designed to be lightweight and impact resistant. These lenses are usually used for children or sportswear.
However, high-index lenses are less light and impact-resistant than polycarbonate or Trivex lenses. This disadvantage also makes them unsuitable for drill-mount (rimless) frames.
Reflects More Light
High-index lenses can reflect up to 50% more light than regular plastic lenses. Many optical retailers often include anti-reflective coatings with high-index lenses to reduce glare.
Types of High-Index Eyeglasses
High-index lenses can be combined with many other features and lens types. Some of those options include the following:
- Aspheric lenses: Slimmer and help to minimize the edge thickness, particularly on high myopic prescriptions
- Photochromic lenses: Clear indoors and turn dark when you go outside to block 100% of UV rays and reduce glare
- Polarized lenses: Reduce glare off horizontal surfaces, such as road surfaces and water
- Bifocal lenses: Suitable for those who are presbyopic and need reading correction.
- Progressive glasses: Provide distance, intermediate, and near correction.
High-definition lenses. Also known as digital lenses, these are highly customized lenses that deliver higher-quality vision than traditional lenses.
Common Questions on High Index Lenses
Are high-index lenses better than polycarbonate?
High-index lens material is a great option for stronger prescriptions, as they are thinner and lighter. However, polycarbonate is more impact-resistant, making them a better option for sports, protective, and children's frames.
Are high-index lenses worth it?
High-index lenses do cost more than regular polycarbonate lenses. However, people with strong prescriptions will likely find the additional cost worth it since high-index lenses are much thinner, lighter, and aesthetically pleasing.
Why are high-index lenses so expensive?
High-index lenses are more expensive to manufacture and more difficult to grind, making them more expensive than other types such as polycarbonate.
Do high-index lenses cause distortion?
It is possible that high-index lenses cause slight distortion in your peripheral vision due to their low Abbe value.
Is there a big difference between 1.67 and 1.74 high-index lenses?
1.67 index lenses are suitable for prescriptions under +5.00/-8.00 and astigmatism correction between -3.00 and -4.00. 1.74 index lenses are the thinnest high-index lenses. This lens is suitable for stronger prescriptions above +5.00/-8.00 and astigmatism correction between -4.00 and -6.00.
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