Do you find all of the lens material options confusing when you order new glasses? With seven different options at Zenni, it can be overwhelming if you don’t know what you need.   The nice thing about the  Zenni checkout is that when you enter your prescription, the website is configured to recommend the thinnest lens for your eyeglasses.

Even though having a recommendation makes shopping for the right lens easy, we want you to understand the different specifications for each lens type and lens material.  Let’s take a look at the lenses we offer, the various prescription types, and the prescriptions within those types the lenses cover.  

Single Vision vs Multifocal

Each optical lens we offer accommodates a specific  prescription range. The two broad prescription categories are single vision and multifocal (which comprise bifocal and progressive lenses).

For single-vision,  Zenni can cover prescriptions for nearsightedness that go up to -20.00 and farsightedness up to +12.00. Nearsightedness and farsightedness are corrected according to the numbers in the Sphere (SPH) section of a prescription.  You can learn more about how to read your prescription here. 

You may be interested in a multifocal lens if your prescription includes a near add (ADD) power.  Zenni can cover progressive prescription ranges -10.00 / +8.00 and bifocal prescription ranges  -9.00/ +6.00. For progressives, we recommend using lenses that have at least a depth of 30 mm to cover the various fields of vision that come with multifocal lenses. 

A tiny portion of eyeglasses wearers have prism corrections on their prescription. We can fill these for single-vision (not multifocal) prescriptions up to 5.00 in any base direction (base up, base down, base in, or base out) for prescription ranges -12.00 /+6.00. 

Remember that these prescription ranges can be further limited depending on the lens material or index that you choose.  Read below to learn about the different lens index options you can find at  Zenni from thickest to thinnest.

Lens Index Options

Zenni offers several different lens index options from thickest to thinnest.

1.50 Standard Index

This is our most basic lens type. It’s ideal for low prescriptions in the range of +1.00/-2.75 or below. If you have an extremely mild prescription, the standard index option will deliver the thinnest frame.

This lens is made of CR-39 plastic, which is a polymer (a large molecule composed of many repeated subunits, known as monomers). HEre’s a fun fact, CR-39 gets its name because it was the 39th formula of a plastic developed by the Columbia Resins (hence “CR”) project in 1940. It was first used to help create glass-reinforced plastic fuel tanks for the B-17 bomber in World War II.

Keep in mind that the 1.50 lens index only features 85%-90% UV protection in a clear lens. For 100% UV protection, you’ll want to select a higher lens index or a more advanced lens option, such as our Blokz blue light blocking lenses.

1.57 Mid-Index

If you have a medium-level prescription, a 1.57 mid-index lens will work well.  This mid-index llens option is free at Zenni and is best for prescriptions +2.00/-3.75 or below. It also features 100% UV protection, which is an added bonus..

Impact Resistant Lenses

Impact-resistant lenses are recommended for children’s glasses, safety glasses, and sports goggles, as well as rimless and half-rim glasses because of their great impact resistance.

Trivex 1.53 

Trivex 1.53 is great for prescriptions +2.00/-3.00 or below and. It’s known for being crisp and clear, more scratch resistant, and 10% lighter than polycarbonate lenses. Our Blokz Trivex lenses are perfect for protecting young eyes from the harmful blue light that’s emitted from digital screens while also providing durable impact resistance. 

Polycarbonate 1.59 

Polycarbonate 1.59 lenses also feature great impact resistance and work best if your prescription is +3.00/-4.75 or above. In terms of thinness, this lens index is thinner than 1.50 lenses. They’re  more affordable than Trivex and are only moderately heavier. However, the clarity in polycarbonate lenses is slightly less than Trivex and they tend to scratch more easily. 

High Index 1.61, 1.67 and 1.74

If you have a medium or strong prescription, you need a high-index lens to keep your lenses thin. High-index lenses have good optical clarity, 100% UV protection, and excellent durability. They currently come in indices of 1.61, 1.67, and 1.74. All three lenses are made with similar materials, so the choice of index comes down to your prescription strength. 

• A 1.61 high-index lens is best for +3.00/-5.75 or below. It can even be a good choice for people with low prescriptions who want the additional lens benefits mentioned above. 
• The thinness of a 1.67 high index lens is good if you have a prescription that is +4.75/-6.75 or below.
• A 1.74 high-index lens is the thinnest option for strong prescriptions that are +5.00/-7.00 or above. 

Factors That Affect Lens Thickness

When buying glasses, there are three primary factors that affect your overall lens thickness:

1. Prescription – Your prescription is what will ultimately determine how thick your lenses will be. Simply put, the higher the prescription, the thicker the lens. In addition, prescriptions with moderate to high astigmatism correction often result in thicker lenses.
2. Lens Material or Lens Index – The lens index refers to the “index of refraction,” or how much the lens bends the light that enters it. This ensures that the light is focused properly onto the retina, helping you to see clearly when wearing your glasses. In general, the higher the index, the thinner the lens. (For example, a 1.61 lens is thinner than a 1.50 lens.) During the checkout process at Zenni, choosing a higher lens index will be the most direct way to ensure you have the thinnest lenses possible. 
3. Lens Size – The overall width and height of your lenses can have a considerable impact on the thickness of the lenses themselves. The bigger the lens, the thicker it tends to be. When buying frames at Zenni, the lens width and height are predetermined based on the frame you choose. Aside from choosing frames based on factors like style and face shape, you should also shop based on size, as well as your eye doctor’s recommendations.

Now that you understand the best lens index options for your prescription, you can learn about the different lens options that Zenni offers, such as light darkening and blue light blocking lenses. And if this seems like a lot of information, don’t worry! The lens index that is recommended for your prescription during checkout will be the most appropriate lens choice.