Glass spectacle lenses – i.e. lenses made from natural glass according to their professional classification – used to be the norm. They still have their place in optometry today thanks to their exceptional scratch resistance. Consumers will also like the fact that they are also less expensive than comparable plastics. In cases of severe ametropia, they can also provide the correction needed with relatively thin lenses – an aesthetic aspect that is not to be underestimated.
Natural glass is also recommended for bifocal or trifocal lenses because various materials can be melted together without forming a noticeable cutting edge. In principle, the increased thickness of the material makes it optically purer; the glasses appear cleaner and are free from disruptive colour fringes (so-called dispersion).
When light strikes a spectacle lens, it is broken and dispersed into its component parts. This creates a disruptive visible colour spectrum, similar to a prism. The intensity of this effect, known as dispersion, depends on the condition of the material used: high-quality material = minimal dispersion. The colour fringe effect is measured based on the so-called Abbé number: The higher the Abbé number for a spectacle lens material, the lower the dispersion.
The advantage of natural glass: It produces considerably weaker colour fringes even when the refractive index is identical to that of plastic lenses.
The greater the refractive index range (also called the refraction index) of the spectacle lens material, the thinner the finished glass. For high dioptric values, it is therefore advisable to use a lens material with a high refractive index, as this will reduce the thickness of the lenses and thus the weight of the spectacles. For example: A lens with a refraction index of 1.6 is always thinner than one with a refraction index of 1.5 for an identical dioptric value.
Natural glass has a clear advantage here: Its refractive index range extends from 1.5 to 1.9, while the refractive index range of organic glass (= plastic) is only 1.5 to 1.74. Natural glass also has a greater density than plastic.
The result: Even when the refraction index is the same, spectacle lenses made of glass are always thinner than those made of plastic – but they are also substantially heavier.
FAQs
Clarity. Glass lenses provide the clearest vision with the smallest amount of distortion. Scratch resistance. Glass lenses are almost impossible to scratch, while plastic lenses can be scratched easily if you are not careful.
How do you tell if your lenses are glass or plastic? ›
A popular and accessible method for discerning lens material involves tapping the lens against your teeth—a tool always at hand. Glass typically produces a soft ringing sound upon contact, while plastic elicits a subdued thunk. A ringing sound indicates glass, while a thunk confirms plastic.
Do you use glasses or contact lenses answer? ›
Many people opt for contacts during the day and then return to their glasses during the morning and night. Others just do what they feel, and switch between glasses and contacts spontaneously. The point is, there's really no right choice between the two—and in fact, choosing both nets you the best eyesight and comfort.
How to tell if costas are glass or plastic? ›
Costa glass lenses have a "580" etching on the top left of the lens. Costa polycarbonate lenses have a "580P" etching on the top left of the lens. So if there isn't a "P" on the lens, the lenses are made of glass.
What type of lens do most doctors recommend? ›
Your type of vision problem will determine the shape of your lens. You'll need a concave lens (curves inward) if you're nearsighted. A convex lens (curves outward) will help if you're farsighted. If you have astigmatism, your cornea is shaped wrong, so your lenses may be more like a cylinder.
Which lenses are best for eyes? ›
Progressive lenses have clear benefits compared to bifocal and trifocal lenses. Progressive lenses have a power for the near, intermediate and distance zones – and all of this in a lens with a seamless transition and no dividing line. The power is smooth from top to bottom and moves from distance to near vision.
Do contact lenses give better vision than glasses? ›
Contacts: Pros
They give you more natural vision than glasses. They move with your eye, and nothing blocks what you see.
Is it better to wear glasses or contacts to an eye exam? ›
The answer is usually yes unless your doctor specifically tells you otherwise. Wearing your contacts will help your doctor get a more accurate measure of your prescription and determine if your lenses are causing any problems.
Why choose glasses over contacts? ›
Eyeglasses offer many benefits over contact lenses. They require very little cleaning and maintenance, you don't need to touch your eyes to wear them (decreasing your risk for eye infections), and glasses are cheaper than contact lenses in the long run since they don't need to be replaced as often.
Is Maui Jim better than Costa? ›
If you read reviews on Costa Del Mar and Maui Jim, you will find that Maui Jim is a clear winner. There are many posts on various forums in social media that demonstrate the long waiting times and cumbersome customer service policy of Costa.
When it comes to UV rays, both Costa and Oakley glasses offer 100% UV protection. According to the American National Standards Institute, Oakley has a rating of ANSI Z87. 1, while Costa is rated at ANSI Z80.
Are Costa glass or plastic lenses better? ›
Costa makes 580 lenses: available in glass or polycarbonate as indicated by a G (glass) or P (polycarbonate) after the model number. Glass offers the greatest clarity and resists scratching better than polycarbonate lenses. But polycarbonate lenses are lighter weight, resist impact, and they're more durable.
What is the best material for eyeglass lenses? ›
1.67 High Index Plastic
1.67 high-index plastic is an ideal option if you have a high prescription, as it is the thinnest option available for lenses. It is a slightly more expensive option than CR-39 or polycarbonate, but it provides exceptional optical performance due to its index of refraction of 1.67.
What are the disadvantages of plastic frames? ›
They break more easily than metal frames and they can potentially burn (although it is difficult to ignite plastic lenses). If you are investing in plastic glasses, make sure you are buying good plastic made of modern blended materials.
Are glass or plastic lenses more expensive? ›
Plastic lenses don't have nearly the scratch resistance level glass does. Some plastic lenses can get scratch prevention, though it costs extra money you may not want to spend. Since glass lenses are already less costly than polycarbonate options, you don't have to spend extra money to get automatic scratch protection.
Which contact lens material is good for eyes? ›
A HyperGel material unites the goodness of Hydrogel and Silicone Hydrogel materials without having the demerits of either of these materials. This material is positioned as a 2Bioinspired material due to its water content same as the cornea and having dehydration control just similar to natural tears.
