How to get the thinnest lenses for your prescription

Unless you’re going for a look that says, “Kick me, I’m a nerd,” you probably want a pair of glasses with the thinnest lenses possible.

But if you have a heavy prescription and are ordering your glasses online, figuring out how to get the thinnest lenses possible can be perplexing.

It is not to worry.

We are going to make it easy for you.

All you need is your prescription and a handy online tool that will calculate how thin your lenses will be.

This handy online tool is the Lens Thickness Calculator. It can be found on the OptiCampus website.

Before we talk about how to use the Lens Thickness Calculator, let’s look at the factors that can thin your lenses:

1. your recipe. This cannot be changed to get a thinner lens. Doing so would be counterproductive, as you would not be able to see well if you make the decision to reduce your prescription below what your ophthalmologist has prescribed.

As a general rule, single vision prescriptions result in thinner lenses than multifocal prescriptions, all other things being equal. Multifocal prescriptions are those with a NV-ADD (NOear vvision reading ADDition). have a NV-ADDor just a ADDas it is usually written, it allows you to get bifocal and progressive glasses.

Also, prescriptions with astigmatism corrections – if you have this, there will be numbers on the Cylinder (CYL) Y Axis (sometimes abbreviated X) – generally result in thicker lenses than those without astigmatism corrections.

2. Your lens index. The “index” of the lens is short for the “refractive index” of the lens. That means how much the lens bends the incoming light. That is refraction. Bending the light focuses it right in the center of your visual sweet spot, the retina, so you can see well.

You can change the index to thin the lens, up to a point. After that point, the law of diminishing returns kicks in. The lens that is recommended for your prescription will be the thinnest lens. Choosing a lens index that is higher than the recommended lens index will not make the lens thinner and you will end up paying more for not improving the result.

If this is confusing, don’t worry. We will clearly explain where the point of diminishing returns appears when we look at the various lens indices. In addition, you will also be able to see it when you start playing with the Lens Index Calculator.

3. The width of your lens. This can have a considerable effect on the thinness of your lens. Once you have settled on the correct lens index, having determined that going to a higher lens index number will not result in a thinner lens, the width of the lens (also known, strangely, as the “size of the eye”) will be the last, and in some situations, the most important factor in thinning your lens.

In Part 1, we describe the factors that can make an optical prescription lens slimmer: the refractive index and the width of the lens, also known as “eye size.”

Now let’s look at a prescription to see how different index numbers can make lenses thinner. We’ll change the width of the lens, remember, that’s also known as “eye size” (although it doesn’t refer to the size of your eye), to see how this affects the thinness of the lens.

To do this, we are going to use a fairly common recipe. Most eyeglass wearers are myopic, which means that the number on the Sphere (HPS) prescription section will be less.

Most people who have a HPS correction also have an astigmatism correction. So let’s create a common prescription, with an average pupillary distance (i.e. the distance between the pupils measured in millimeters, database for short), 63; an average lens width (all together now: aka “eye size”), 50mm; and a medium bridge (that’s the part of the frame that goes over the nose), 18mm.

Here it is:

SPH -2.00, CYL -1.00, AXIS 90, PD 63, Lens Width 50, Bridge 18.

(For the sake of simplicity, we will assume that the prescription is the same for both eyes.)

Let’s put these numbers into the Lens Thickness Calculator and see what we get when we use different lens indexes.

With myopic prescriptions, the lens is concave. With farsightedness prescriptions, the lens is convex. A concave lens is thinner in the center and thicker at the outer edge. A convex lens is the opposite.

You will see then, that with nearsighted prescriptions, the Center Thickness of the lens will be a smaller number than the Edge Thickness.

Here’s what our formula produces with the standard 1.50 index lens, which comes free with a single vision order:

Center Thickness (CT): 2.0mm / Edge Thickness (ET): 4.4mm

Nice and thin in the center, but maybe not as thin as it could be on the outer edge. Let’s try it with the 1.57 mid-index lens and see what we get:

CT: 1.5mm / ET: 3.6mm

That makes the lens thinner both in the center and on the edge, and the lens is still free. Now let’s try it with the 1.59 pure polycarbonate single vision lens, which costs $9.00, and see what happens:

CT: 1.5mm / ET: 3.5mm

You’re spending $9.00 for this lens, which isn’t a huge amount, but this slightly higher index doesn’t make the eyeglass lens noticeably thinner than the free 1.57 lens. Now we are beginning to see how the law of diminishing returns comes into play.

However, even if the lens were just as thin with the 1.57 lens, it would be worth spending the $9.00 on the 1.59 pure polycarbonate lens if you buy rimless glasses or if you buy glasses for children who may be expected to treat the glasses abruptly.

This is because the 1.59 lens is a more impact resistant lens than the 1.57, which is still a good lens for people who treat their glasses with care.

Now let’s really see how the law of diminishing returns works when we go up a notch, up to 1.61 high index single vision lenses. Here are the results of this lens:

CT: 1.5mm / ET: 3.5mm

No change, you’re now (theoretically) spending $19.95 on a lens that’s no thinner than the 1.59 pure polycarbonate lens that costs $9.00, and only a tiny bit thinner than the free 1.57 mid-index lens.

But even after you have selected the lens index that will give you the thinnest lens, you can still make the lens even thinner by reducing its width.

Let’s reduce the width of the lens to 48mm and see what happens with each lens. First, the 1.50 lens:

CT: 2.0mm / ET: 4.1mm

The rim thickness is slightly better, 4.1mm instead of 4.4mm on the 50mm wide lens. What about the 1.57 lens?

CT: 1.5mm / ET: 3.3mm

Now we are talking! We’ve shaved off half a millimeter from the center and almost a whole millimeter off the edge, simply by lowering the width of the lens.

How about with the 1.59 lens?

CT: 1.5mm / ET: 3.2mm

No change in the center, just a tenth of a millimeter on the edge. Stand up and salute the diminishing returns on parade!

Let’s take a quick look at the 1.61 lens, just to make sure it doesn’t make theoretical eyeglass lenses thinner:

CT: 1.5mm / ET: 3.2mm

That would cost $10.95 more if the result is not improved.

So unless you want a pure polycarbonate lens for its impact resistance feature, you’re wasting your money by spending $9.00 to get a higher index 1.59 lens that won’t be any thinner than the free 1.57 index lens medium.

But once you’ve confirmed which lens index will result in the thinnest lens for your prescription, and you want to thin the lens further, play around with the lens width in the Lens Thickness Calculator. Go as low as you can and still keep the lenses wide enough for a comfortable field of vision and an attractive appearance.

For example, the 48mm wide lens can be as narrow as possible without making the glasses look too small. But if you can make the lens even narrower, you will see that the lens will keep getting thinner.

If you refer to the Lens Thickness Calculator for estimates of different thicknesses that different lens indexes and lens widths produce, keep a few things in mind: When you select the Lens Material Type, the categories listed in the Thickness Calculator Lens No. They do not exactly correspond to the lens index categories on our website, although they are basically the same.

For example, the hard resin lens is the 1.50 lens. The mean index of 1.56 is essentially the same as the mean index of 1.57. The polycarbonate lens is the 1.59 medium index lens. All 1.60 lenses in the Lens Material Type list are equivalent to 1.61 High Index lenses.

So, to recap, stick with the lenses our website recommends when you enter your prescription. That will give you the thinnest lens for your prescription, if you also select the lowest lens width that will also work well for your face size and shape.

Good luck.