The lenses you choose for your spectacles — even more than frames — often will determine how happy you are with your eyewear.
And buying spectacle lenses is not an easy task. In fact, there are so many choices for lenses and coatings, that it’s easy to be confused about all the choices.
This buying guide will help you cut through the hype about different types of spectacle lenses, and help you choose lenses and coatings that offer the best features and value for your needs. You can also view our educational videos on spectacle lenses if you’d like to learn more.
Why Choosing The Right Spectacle Lenses Is So Important
When buying spectacles, the frame you choose is important to both your appearance and your comfort when wearing spectacles. But the spectacle lenses you choose influence four factors: vision, appearance, comfort and safety.
Spectacle lens thickness is determined in part by the size and style of the frame you choose. For thinner lenses, choose smaller, round or oval frames. Also, plastic frames hide edge thickness better.
A common mistake people often make when buying spectacles is not spending enough time considering their choices of spectacle lens materials, designs and coatings.
Plastic lenses
In 1947, the Armorlite Lens Company in California introduced the first lightweight plastic spectacle lenses. The lenses were made of a plastic polymer called CR-39 (index=1.498), an abbreviation for “Columbia Resin 39,” because it was the 39th formulation of a thermal-cured plastic developed by PPG Industries in the early 1940s.
Because of its light weight (about half the weight of glass), low cost and excellent optical qualities, CR-39 plastic remains a popular material for spectacle lenses even today.
Polycarbonate lenses
In the early 1970s, Gentex Corporation introduced the first polycarbonate lenses (index=1.586) for safety spectacles. Later that decade and in the 1980s, polycarbonate lenses became increasingly popular and remain so today.
Originally developed for helmet visors for the Air Force, for “bulletproof glass” for banks and other safety applications, polycarbonate is lighter and significantly more impact-resistant than CR-39 plastic, making it a preferred material for children’s eyewear, safety spectacles and sportswear.
Trivex lenses
A newer lightweight spectacle lens material with similar impact-resistant properties as polycarbonate is called Trivex (index=1.54), which was introduced for eyewear in 2001. Trivex® material was developed to produce a unique combination of patient benefits: lightweight, improved protection, thin, superior clarity of vision and full UVA/UVB protection compared with older lens technologies.
High-index plastic lenses
In the past 20 years, in response to the demand for thinner, lighter spectacles, a number of lens manufacturers have introduced high index plastic lenses (index=1.6 to 1.74). These lenses are thinner and lighter than CR-39 plastic lenses because they have a higher index of refraction (see below). Because high index lenses can form prescriptions using less physical material, they provide lenses that are both lighter and thinner than identical lenses formed out of standard glass or plastic. If you have a very slight corrective prescription, you might not enjoy much of a boost here; however, the stronger your prescription gets, the more benefit you’ll receive. A lens that would be extremely thick and heavy if made of standard material can be considerably thinner and lighter if formed of high index material.
Index Of Refraction
The higher the refractive index of a material, the slower light moves through it, which results in greater bending (refracting) of the light rays. So the higher the refractive index of a lens material, the less lens material is required to bend light to the same degree as a lens with a lower refractive index.
In other words, for a given spectacle lens power, a lens made of a material with a high refractive index will be thinner than a lens made of a material with a lower refractive index.
Popular types of lenses
Single vision lenses
Single vision lenses have one single prescription across their entire surface and are suitable in all scenarios, whether you need your spectacles for driving, working or reading.
If you need to wear spectacles for both distance and near vision, you could wear separate pairs of single vision spectacles dedicated to each task. However, the preferable option would be to consider the benefits of bifocals or progressive lenses.
Myopia Management Spectacle lenses
Spectacle lenses for myopic management are specially designed lenses which correct vision and reduce axial length progression by approximately 39-60%. These lenses incorporate different lens technologies such as the lenslet design, diffusion technology or diffusion Optics Technology DOT. Axial elongation correlates with myopia progression. Myopia management is critical in reducing the risk of sight-threatening conditions such as retinal detachments, glaucoma, myopic maculopathy and cataracts.
Bifocal lenses
A bifocal lens provides distance and near vision in one lens. The near vision correction of the lens is contained in a segment, often visible on the front of the lens. This segment provides the extra power necessary for you to read clearly.
Bifocals may still leave a gap for mid-distance vision; and, as a line dividing the lens is visible, some customers feel bifocals are not as cosmetically appealing.
Progressive lenses
Progressive lenses are recommended for the convenience of having natural vision at all distances in one pair of spectacles. Progressive lenses have a great cosmetic appearance with no visible line on the lens, unlike bifocal lenses. Our range of progressive lenses ranges from our entry-level lenses to our more popular range with advanced optimised lens design to improve the fields of vision with minimal soft focus(areas of less than 100% clear focus).
Occupational Progressive Lenses
Occupational progressive lenses provide larger intermediate and near reading zones. These lenses are suitable for individuals who spend long hours working at intermediate and near distance ranges in indoor environments. Consult us to discuss your workplace ergonomics and we will dispense the best occupational progressive lens to suit your visual requirements.
Lens enhancements
Photochromatic Lenses
This lens treatment enables spectacle lenses to darken automatically in response to the sun’s UV and high-energy visible light rays, and then quickly return to clear (or nearly clear) when indoors. Photochromatic lenses are available in virtually all lens materials and designs and is more popularly known as Transitions.
Anti-Reflective Coating
Removes reflections for clearer vision and great appearance.
The curved surface of spectacles lenses, along with the materials they are made from, cause reflections. In fact, you can lose around 10% of light through reflections on lenses. These reflections can be distracting and appear unattractive.
An anti-reflective coating allows for clearer vision by reducing reflections, allowing 99.8% of the light through the lens and ensuring distractions to your vision are minimal. Your spectacles’ appearance is also improved, as others can see your eyes rather than reflections of light.
High Refractive Index Lenses
Thinner for improved appearance, lighter for more comfort.
We recommend High Refractive Index lenses to give you the best looking and most comfortable spectacles possible.
Lenses can be made of various materials of varying weight and thickness – the overall result depends on the density of the lens material as well as your personal prescription. As a general rule, if you are long sighted your lenses are thickest in the middle, and the opposite is true if you are short-sighted (the lenses are thickest at the edges).
High Refractive lenses reduce the overall thickness of your lenses, giving them a lighter feel and improving appearance.
UV-Blocking Treatment
Cumulative exposure to the sun’s harmful ultraviolet radiation over a person’s lifetime has been associated with age-related eye problems including cataracts and macular degeneration.
For this reason, people should protect their eyes from UV beginning in early childhood. Thankfully, polycarbonate and nearly all high-index plastic lenses have 100 percent UV protection built-in, due to absorptive characteristics of the lens material.
But if you choose CR-39 plastic lenses, be aware that these lenses need an added coating applied to provide equal UV protection afforded by other lens materials.
Scratch Resistant Coating
Scratch-resistant lenses provide protection from everyday accidental damage. The hard coating prolongs the life of the lens, whilst simultaneously providing clearer vision.