Here are the specific single-vision lenses, with the prescriptions they accommodate.
For the mildest of single-vision prescriptions, those ranging from -2.00 to +1.00 or lower on the SPH and +/- 2.00 or lower on the CYL, the recommended lens is the 1.50 standard-index lens.
This lens is made of CR-39 plastic. CR-39 plastic is a polymer (a polymer is a large molecule composed of many repeated subunits, known as monomers) that gets its name because it was the 39th formula of a plastic developed by the Columbia Resins (hence “CR”) project in 1940. The first use of this plastic was to help create glass-reinforced plastic fuel tanks for the B-17 bomber in World War II.
CR-39 plastic has an index of refraction of 1.498, rounded up to 1.50 in the optical world.
Another lens available for single-vision prescriptions is the 1.57 mid-index lens. This lens is often described as “polycarbonate composite,” because in addition to polycarbonate the lens is composed of other polymers and resins that keep the lens thinner than the 1.50 lens. Its range is -4.00 /+2.00 or lower on the SPH and +/- 6.00 or lower on the CYL.
The 1.53 mid-index Trivex lens is a polymer lens that is the most impact-resistant lens available. It covers the same range as the 1.57 mid-index lens: -4.00/+2.00 or lower on the SPH and +/- 6.00 or lower on the CYL. It’s recommended for rimless, children’s, and sports eyeglasses because of its unequaled impact resistance.
However, unlike the 1.50 and 1.57 lenses, it cannot be tinted.
If $29.95 is more than you would want to spend on an impact-resistant single-vision lens, the 1.59 pure polycarbonate lens, for $9.00, may be preferable. It covers the same prescription range as the 1.57 polycarbonate composite and 1.53 Trivex lenses, -4.00/+2.00 or lower on the SPH and +/- 6.00 or lower on the CYL. Also, it’s the second most impact-resistant lens available, just down a notch on impact resistance from the 1.53 Trivex lens, making it a good, less-expensive alternative for rimless, children’s, and sports eyeglasses.
However, like the 1.53 Trivex lens, it cannot be tinted, although it is available in glare-reducing polarized sunglasses and photochromic “auto-tinting” lenses, which turn dark in the bright sunlight and become clear again when you are out of the sun.
Occasionally, some people who have rimless or half-rim glasses with 1.59 pure polycarbonate lenses have reported some chromatic aberration, meaning rainbow-like reflections, around the outer edge of the lens.
In addition, the 1.59 pure polycarbonate lens tends to scratch more easily than the 1.50, 1.57, and 1.53 lenses, because it’s a softer lens material.
The 1.61 high-index polymer single-vision lens provides a thinner lens for stronger prescriptions than mid- and standard-index optical lenses do. It is suitable for SPHs of -6.00/+3.00 or lower and, like all the others except for the 1.50 standard-index lens, CYLs that go up to +/- 6.00.
A high-index lens reduces the edge thickness for nearsighted (-) prescriptions and the center thickness for farsighted (+) prescriptions. In addition, it has a flatter, aspheric lens surface, which improves the visual quality the wearer experiences while reducing distortion of their eyes when others are looking at you.
Next comes the 1.67 high-index polymer single-vision lens. It provides a thinner lens for prescriptions than the 1.50 standard-index, 1.53 Trivex, 1.57 mid-index, 1.59 polycarbonate, and the 1.61 high-index lenses. It covers SPHs of -20.00/+10.00 or lower and CYLs of +/- 6.00 or lower.
Just like the 1.61 high-index lens, the 1.67 lens reduces the edge thickness for nearsighted (-) prescriptions and the center thickness for farsighted (+) prescriptions. And just like the 1.61 high-index lens, its aspheric lens surface improves the visual quality the wearer experiences while reducing distortion of the wearer’s eyes as seen by others.
The highest index single-vision plastic lens is the 1.74 high-index polymer lens. It’s for nearsighted (-) single-vision prescriptions only. It provides a thinner lens for SPHs of -8.25 to -10.00 or lower and covers CYLs of +/- 4.00 or lower.
Just like the 1.53 mid-index Trivex and 1.59 polycarbonate lenses, the 1.74 lens cannot be tinted. It’s unavailable as a polarized or photochromic lens. Like the 1.61 and 1.67 high-index lenses, it has an aspheric surface, improving the eyeglasses wearer’s visual quality while reducing distortion of the wearer’s eyes as seen by others.
Anti-reflection coatings are good for any optical lenses, but they are especially recommended if you’re getting high-index lenses. They reduce glare and reflection and allow more light to pass through the lens, improving contrast, which improves visual acuity.
That covers single-vision lenses.