What Is The Formula For Area Of A Sphere Which Prescriptions Go With Which Lenses?

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Which Prescriptions Go With Which Lenses?

You order glasses online.

You enter your order and your child’s distance. (Pupil distance, abbreviated PD, is the distance from the center of the pupil to the center of the other pupil. It is necessary as your prescription to get glasses online.)

The website you order from reads these factors and then recommends a lens for your glasses.

How do you know which lens is right for you?

Here’s how. Each optical lens, from standard index to high index, from single vision to multifocal, takes a certain range of regulation.

Let’s take a look at the different prescription lenses offered by vendors, the different types of prescription medications, and the prescriptions among those types of lens covers.

The two broad types of lenses are single vision and multifocal. Multifocal lenses include bifocals and progressives.

Nearsightedness and farsightedness are corrected according to the numbers in the Sphere section (SPH) of the prescription. Single vision prescriptions for near vision can be filled up to -20.00, far vision up to +12.00.

If you have astigmatism, this will be indicated on your prescription by the numbers on the Cylinder (CYL) and Axis (sometimes abbreviated “X”). For single vision prescriptions, this means that those who do not have numbers in the Near-Vision Reading Addition section (NV-ADD or simply ADD), the regulations in the CYL section can be filled up to + or – 6.00. The numbers on the Axis or X-section simply refer to the angle at which the CYL, an actual cylinder invisible to the wearer, is placed on the lens.

A small proportion of people who wear glasses have prism corrections in their prescription. These can be filled in single vision prescriptions (not multifocal) up to 5.00 in any base method (base, base, base, or base).

For people who have numbers in the NV-ADD section of their prescription and want to get a type of multifocal glasses known as bifocals, which are eyeglasses with a lined reading-addition segment at the bottom of the lens, prescriptions for immediate vision can be filled. up to -9.00 and far vision up to +6.00. You can go up to +3.50 for NV-ADD.

A type of multifocal glasses known as progressives are glasses that have no visible line between three distinct focus areas, namely distance (driving and watching TV) vision at the top of the lens, intermediate (computer) vision at the center of the lens, and near (reading) vision at the bottom of the lens.

Prescriptions can be filled with higher progressive corrections than bifocals. Most progressives go up to -10.00 for near vision and up to +8.00 for distance vision. Just like bifocals or single vision glasses, the CYL correction goes up to + or – 6.00. And as with bifocals, the NV-ADD increases to +3.50.

Here are single vision lenses, and the prescriptions they receive.

For the smallest prescription of single vision, those ranging from -2.00 to +1.00 or less SPH and +/- 2.00 or less CYL, the recommended lens is a standard-index lens of 1.50.

This lens is made of CR-39 plastic. CR-39 plastic is a polymer (a polymer is a large molecule made of many repeating units, known as monomers) that gets its name because it was the formula 39 plastic that was developed by Columbia Resins (hence “CR”) project in 1940. The first use of this plastic was to help making 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 to 1.50 in the optical world.

Another lens available for single vision prescriptions is the 1.57 medium index lens. This lens is often described as “polycarbonate composite,” because in addition to the polycarbonate lens it is made of other polymers and resins that keep the lens smaller than the 1.50 lens. Its range is 4.00 /+ 2.00 or less for SPH and +/- 6.00 or less for CYL.

The Trivex 1.53 mid-index lens is the most impact resistant polymer lens available. It covers the same range as the 1.57 index lens: -4.00 / + 2.00 or less in SPH and +/- 6.00 or less in CYL. It is recommended for rimless, children’s, and sports glasses because of its even resistance. However, unlike the 1.50 and 1.57 lenses, it cannot be tinted.

If $29.95 is more than you might want to spend on a nonprescription single vision lens, the $1.59 clear polycarbonate lens, for $9.00, is an option. It includes the same range of trees as 1.57 polycarbonate composite and 1.53 ​​Trivex lens, -4.00 / + 2.00 or less SPH and +/- 6.00 or less CYL. It’s also the second most impact-resistant lens available, just down a notch in impact resistance from the 1.53 Trivex lens, making it the best, most affordable option for rimless, children’s, and sports eyewear.

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 sunlight and clear again when you are out of the sun. .

Occasionally, some people with rimless or half-rim glasses with 1.59 clear polycarbonate lenses have reported chromatic aberration, meaning a black-like reflection, on the outer edge of the lens.

In addition, the 1.59 clear polycarbonate lens tends to scratch more easily than the 1.50, 1.57, and 1.53 lens, because it is a softer lens material.

The 1.61 high-index polymer optical lens provides a less powerful prescription lens than mid-and-standard-index optical lenses do. It is suitable for SPHs of -6.00 / +3.00 or less and, like all other except the standard-index lens of 1.50, CYLs of +/- 6.00.

A high index lens reduces the thickness of the edge of the near-sighted (-) lines and the central thickness of the far-sighted (+) lines. In addition, it has a flat, aspheric lens, which improves the visual quality of the wearer while reducing the distortion of their eyes when others look at you.

Next comes the 1.67 high polymer single vision lens. It offers a smaller prescription lens than the 1.50 standard-index, 1.53 Trivex, 1.57 mid-index, 1.59 polycarbonate, and 1.61 high-end lenses. Includes SPHs -20.00/+10.00 or less and CYLs of +/- 6.00 or less.

Just like the high-index 1.61 lens, the 1.67 lens reduces the edge size of near-sighted observations (-) and the intermediate size of far-sighted observations (+). And just like the high-index lens of 1.61, the aspheric lens surface improves the visual quality of the wearer while reducing the distortion of the wearer’s eyes as seen by others.

The maximum index for a single vision plastic lens is 1.74 for a high polymer lens. It is for nearsighted (-) single vision instructions only. It offers small lens SPHs of -8.25 to -10.00 or lower and covers CYLs of +/- 4.00 or lower.

Just like the 1.53 between the Trivex index and the 1.59 polycarbonate lenses, the 1.74 lens cannot be lowered. Not available as a polarized or photochromic lens. Like the 1.61 and 1.67 high index lenses, they have an aspheric surface, improving the wearer’s visual quality while reducing the wearer’s eye distortion as seen by others.

Anti-reflection coatings are good for any contact lenses, but they are especially recommended if you are getting premium lenses. They reduce glare and reflection and allow more light to pass through the lens, improving contrast, which improves visual perception.

That covers single vision lenses.

For bifocals, the most common type is the 28 D-style flattop near the reading section of the lens. That means the top part of the bifocal lens is flat and the bottom is curved, which makes the bifocal lens look like a capital letter D on its side. It is called “flattop 28” because the widest part of the bifocal segment lens is 28 millimeters (mm) in diameter.

One of the bifocal lenses is a 1.50 standard-index bifocal lens in CR-39 plastic. It’s just like a 1.50 standard single vision lens, except it has a bifocal component. This lens is good for SPHs of -3.00 / +1.50 or lower with CYL of +/- 6.00 and ADD of +3.50 or lower.

The bifocal segment line is located 2 mm below the center of the lens. So if you get a lens with a length of 30 mm, the bifocal section will be 13 mm from the bottom, 2 mm below the center line of 15 mm.

The 1.61 high index aspheric bifocal polymer lens offers a small prescription lens with SPHs of -9.00 / +6.00 or less and CYLs of +/- 6.00 or less and an ADD of +3.50 or less.

As one of the top lens considerations, an anti-reflection coating is recommended for top bifocal lenses.

Now let’s look at progressive lenses.

Progressive glasses (non-linear multifocal) follow the same pattern as single vision lenses in terms of the direction of the distance part of the lens. They deviate slightly from bifocals in the near reading section. Progressive lenses in the so-called “free-form” style have a reading passage of about 14 mm, about half the width of a bifocal lens.

1.50 standard-index progressive CR-39 plastic lens covers SPHs of -2.00 / +1.00 or lower and CYL of +/- 6.00 or lower, and ADD power +3.00 or less. 1.57 middle-index progressive polymer lenses include SPHs of -4.00/+2.00 or lower, CYLs of +/- 6.00 or lower, and ADD power of +3.50 or lower.

The 1.53 mid-index Trivex progressive lens, like the Trivex single vision lens, has the highest impact resistance of all the lenses we carry. Also like the Trivex single vision lens, this lens cannot be tinted. It is slightly smaller than a standard-index 1.50 index lens. Includes SPHs of -4.00 / +2.00 or less, CYLs of +/-4.00 or less, and ADD power of +3.00 or less. Rimless and sports glasses are recommended, but unlike Trivex single vision lenses, they are not recommended for children, who are prescribed multiple glasses only in rare cases.

The features of progressive lenses, 1.59 middle-index pure polycarbonate progressive lens, and high-index 1.61 and 1.67 lenses, follow the same pattern as the single-vision lens. 1.59 progressive lenses, which, like Trivex lenses, cannot be tinted (although they can be ordered as polarized, glare-reducing sunglasses or as photochromic, “auto-tinting” lenses), covering SPHs of -4.00 / + 2.00 or less, CYLs of +/- 4.00 or less, and ADD of +3.00 or less.

High index 1.61 progressive polymer lenses include SPHs of -6.00 / +3.00 or lower, CYLs of +/- 6.00 or lower, and ADD of +3.00 or lower. A high index 1.67 continuous polymer lens includes SPHs of -10.00 / +8.00 or lower, CYL of +/- 6.00 or lower, and ADD of +3.00 or lower. Like single vision lenses, anti-reflection lenses are recommended with high index lenses.

Now you know all the features of all prescription lenses.

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