What are polycarbonate lenses: All the details explained

by Courtney Dryer, OD, May 21, 2024

What is a Polycarbonate Lens Used for?

Polycarbonate lenses can be used for many types of eyewear because of their durability, thin edge profile, and high impact resistance. Some common uses include:

• Safety glasses and goggles: Polycarbonate lenses protect against impact, so they are the standard material for the safety glasses or goggles required for construction sites, laboratories, and manufacturing facilities.
• Sports eyewear: Athletes often opt for polycarbonate lenses to withstand impact from balls, equipment, or falls. Polycarbonate reduces the risk of eye injury during sports activities like baseball, cycling, skiing, and shooting.
• Children's eyewear: Polycarbonate lenses are the standard for children's glasses, protecting their eyes while playing. They are durable and resistant to breakage.
• Children's eyewear: Polycarbonate lenses are the standard for children's glasses, protecting their eyes while playing. They are durable and resistant to breakage.
• Sunglasses: Polycarbonate lenses have inherent UV protection, making them a popular choice for sunglasses. Their lightweight and impact-resistant properties also make them ideal for outdoor activities in the sun.
• Prescription eyewear: Many opticians and eyewear manufacturers offer polycarbonate lenses as an option for prescription glasses due to their durability and lightweight design. Patients with reduced vision in one eye due to a history of trauma, amblyopia, or another condition should always have polycarbonate lenses to protect the vision in their better-seeing eye. Polycarbonate also protects against the windshield or an airbag if a monocular patient is in a car accident.

How are Polycarbonate Lenses Made?

Polycarbonate lenses are produced using a combination of chemical synthesis, molding, and finishing processes.

• Monomer synthesis: The first step involves synthesizing the polycarbonate monomer using a reaction of Bisphenol A (BPA) with either phosgene or diphenyl carbonate. This reaction produces polycarbonate pellets or granules, the raw material for a lens.
• Injection molding: The polycarbonate pellets are melted and injected into lens molds using high pressure. Injection molding allows the manufacturer to control the shape and thickness of the lenses.
• Cooling and solidification: Next, the liquid polycarbonate is rapidly cooled into a solid lens shape. This step ensures that the lens has the correct optical properties and is uniform.
• Surface coating (optional): Polycarbonate lenses made for eyeglasses may undergo an additional process, such as coating with anti-scratch, anti-reflective, or UV-protective coatings, to improve their durability, performance, and overall clarity.
• Finishing: The final inspection is to ensure they meet quality standards. This may include trimming excess material, polishing the lens surface, and verifying the optical properties.

Advantages and Disadvantages of a Polycarbonate Lens

There are several advantages and disadvantages to a polycarbonate lens.

Pros of Polycarbonate Lenses

One of the most significant advantages of polycarbonate lenses is their impact resistance. They may be 10 times more impact-resistant than regular plastic or glass lenses. Polycarbonate lenses are also lighter than glass lenses, which makes them more comfortable to wear for long periods. A pair of glasses with polycarbonate lenses reduces the strain on the wearer's nose and ears, making them more comfortable for those with higher prescriptions. The thin profile of a polycarbonate lens improves the look of the glasses by reducing lens thickness and enhancing one’s appearance. Lastly, polycarbonate lenses inherently block harmful UV rays without needing additional coatings to protect the wearer’s eyes and lids from conditions like cataracts, macular degeneration, and skin cancer.

Cons of Polycarbonate Lenses

While polycarbonate lenses do offer many benefits, they also have some disadvantages. Polycarbonate lenses scratch more easily than glass lenses and CR39 or trivex, resulting in less visual clarity with time. Polycarbonate lenses are slightly more costly than standard plastic lenses but less expensive than Trivex or high-index lenses. Lastly, they are not the best option for someone with a high prescription because the lenses will be thick and heavy, and may result in visual distortion.

How to Know if Glasses are Polycarbonate?

It is difficult to tell if your glasses have polycarbonate lenses without the manufacturer's or eye care professional's specific information. The easiest way to find out is to look at your optical order form or ask your optician. Polycarbonate lenses are known for their high impact resistance, but we would not recommend hitting them as a test. You don’t want to damage your lenses!

Comparison of Polycarbonate Lenses with other materials

Polycarbonate lenses share similarities and differences with other lens materials.

Plastic vs. Polycarbonate Lenses

Plastic lenses are often made from CR-39 and have been the standard for spectacle lenses. They offer high optical clarity and are relatively affordable, making them popular. Plastic lenses are more prone to breaking but are more scratch resistant than polycarbonate lenses. Polycarbonate lenses are significantly lighter and thinner than plastic lenses, improving comfort for those with higher prescriptions. Two major disadvantages of a polycarbonate lens are increased optical distortion and higher cost.

Trivex Lenses vs. Polycarbonate

Trivex and polycarbonate lenses are the two most popular choices for eyewear, each offering unique advantages and characteristics. Trivex lenses are also impact-resistant like polycarbonate but have some other advantages. Trivex lenses have exceptional optical clarity, and minimal distortion and provide crisp, clear vision. Trivex lenses have a higher Abbe value than polycarbonate, meaning they have less chromatic aberration and color distortion, which can be particularly noticeable in the periphery. However, polycarbonate lenses are lighter and thinner than Trivex lenses.

High-Index vs. Polycarbonate

High-index lenses are made from materials with a higher refractive index than standard plastic polycarbonate lenses, allowing them to bend light more efficiently. This enables high-index lenses to be the thinnest and lightest lenses. By reducing the thickness and weight of the lenses, high-index lenses offer improvements in frame and lens aesthetics. They also minimize the magnification or minification of the wearer’s eyes to improve their look. High-index lenses do not typically offer the same level of impact resistance as a polycarbonate lens, nor do they have UV-blocking in the lens.

Glass Lenses vs. Polycarbonate

Glass lenses were once the only option for eyewear. They offer excellent optical clarity and scratch resistance. They also provide sharp, distortion-free vision and are an option for individuals who prioritize visual acuity. Glass lenses also have inherent UV protection properties. It is very difficult, if not impossible, to order glass lenses today because they are heavy and will break if dropped or upon impact.

Who Should Wear Glasses with Polycarbonate Lenses?

Polycarbonate lenses offer benefits that make them preferable for many individuals.

• Those who work in occupations like construction, manufacturing, or in a laboratory where eye protection is crucial.
• Polycarbonate reduces the risk of injury for active children prone to accidents.
• Athletes benefit from the impact resistance and lightweight profile for basketball, baseball, and cycling.
• Eyeglass wearers with moderate prescriptions (+2.00 to -3.00D range) are candidates.
• Those who are monocular and must protect their fellow eyes should wear only polycarbonate lenses. For example, those with a history of reduced vision in one eye due to trauma, injury, or amblyopia.
• Those who desire light, thin, and comfortable eyewear.

What is the Lifespan of Polycarbonate Lenses?

The lifespan of polycarbonate lenses can vary depending on the use, care, and environmental conditions. With proper care, most manufacturers expect 1-2 years of wear until lenses need replacement. Lenses worn daily or in environments exposed to more wear and tear may not last as long. Proper cleaning and storage of polycarbonate lenses will help prolong their lifespan.

How Much Do Polycarbonate Lenses Cost?

The cost can vary depending on the lens manufacturer, your eyeglass prescription strength, lens coatings, and where you purchase them. Polycarbonate lenses typically range in price from $50 to $100 per pair for single-vision lenses. The cost will increase if you opt for additional features like anti-reflective coatings, photochromic, or progressive lenses.

How to Take Care of Polycarbonate Lenses?

Taking care of your polycarbonate lenses is essential to maintain their optical clarity, durability, and longevity. No matter what lens material you order, here are some tips for eyeglass care.

• Use a microfiber cloth. Rough materials like a towel or even your t-shirt can scratch the lenses.
• Use an approved lens cleaning solution or just soap and water.
• Avoid harsh chemicals like bleach or an ammonia-based product as they may damage the material and/or coating.
• Always store your eyewear in its case to prevent scratches or damage. You should never set your lenses face down on a surface or carry them in your purse or pocket without your case.
• Avoid extreme temperatures. Eyewear should never be left in the car. Extreme temperatures can cause stretching of the frame or warping of the lenses.

Conclusion

Polycarbonate lenses are a versatile and practical choice for many eyeglasses wearers. Their impact resistance, lightweight design, and built-in UV protection make them ideal for various professions, active lifestyles, and everyday wear. To read more about polycarbonate lenses or the other types of materials offered at Overnight Glasses, visit our blog.