As far as possible, the sphere lenses should be placed in the back of the frame, closest to the eye.  There is one slot in the back and three slots in the front.  Cylinder lenses are only placed in the front because cylinder lenses have etched lines, and an etched line aligns with a number, which is the axis.

Optical Trial Lens Set Kit

An optical trial lens set kit is needed, and the kit contains the lenses you need for testing eyes.  One or two Jackson cross cylinders are also needed.  You need a 0.25 Jackson cross cylinder.  A 0.50 Jackson cross cylinder might be needed when testing some eyes.  Do not get a lens set kit with plastic rims, because they can not provide a very accurate measurement of the axis.  There is a trial lens set kit which I prefer and I recommend.  It can be ordered from Amazon or from the manufacturer.  It costs more from Amazon, but the delivery time is shorter.  Here is the link for Amazon:

https://www.amazon.com/gp/product/B077BKPBPX/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

And here is the link for the same lens set kit from the manufacturer:

https://www.ucansee.us/collections/all-products/products/ucansee-266-pcs-optical-trial-lens-set-kit-metal-rim-aluminum-case

What I like about the lens set kit is the price, and that it comes with a 0.25 and a 0.50 Jackson cross cylinders, and that it has +/- 0.12 sphere and cylinder lenses.  It is true that eyeglass numbers are only in multiples of 0.25, but still the 0.12 lenses help when it is uncertain which multiple of 0.25 is to be used for the eyeglass numbers.  What I don't like about it is that the etchings on the cylinder lenses for the axis are less accurate than I would like them to be.  I can improve the accuracy by measuring the axis by flipping the cylinder lens over and measuring the axis again, and use the average of the two axis.  More expensive lens set kits are available from the same manufacturer, and they have higher quality lenses, but I do not know if the axis is more accurate or not.

It might be possible to use a smaller lens set kit with fewer lenses, but it is more complicated.  You can combine two lenses together to work as a single lens of the desired strength.  For example, using a +1.00 sphere lens combined with a +0.50 lens works like a +1.50 lens.  Cylinder lenses can also be combined, as long as care is taken to make certain the axis are properly aligned in the frame for both lenses.

Site Survey and Testing Distance

A testing distance of 300 feet is recommended.  Usually this means that the testing must be done outside, looking at trees and brick structures at a distance.  Sometimes the testing can be done inside, looking out an open window.  The window should be open so no glass or screen is in the way.  Sometimes the testing can be done on a porch which is sheltered from the elements.

The reason for recommending 300 feet is that is the distance used for driving.  Senior citizens and older adults whose eyes do not focus much can benefit from the 300 feet testing distance.  The longer testing distance of 300 feet is needed for people of all ages, because it results in more accurate astigmatism measurements.

The ideal for children and young adults is to test at 300 feet, because it results in more accurate astigmatism measurements.  After testing at 300 feet, if the patient is a child or young adult whose eyes still focus on their own for different distances, test a second time at 20 feet changing only the sphere, not the cylinder or axis (astigmatism).

On mission trips, time for testing each individual may be limited.  In this case, senior citizens and older adults should be tested at 300 feet, while younger individuals whose eyes still focus well can be tested at 20 feet.  This is not ideal to test children and younger adults at 20 feet without testing at 300 feet first to get more accurate astigmatism results, but sometimes compromises need to be made in order to test more individuals in a limited time framework.

Testing Prerequisites

Before testing eyesight, the eyes must not be dry.  Carrot juice consumed a number of hours before the test, possibly the night before the test too, can help with dry eyes.  Eye drops also help.  Blinking can keep the eyes moist while testing.  There are some possible indications that maca powder and/or açaí powder might also help with dry eyes.

Do not do any close work, such as reading, for hours before the eye test.  You can do some brief short work, such as glancing at your cell phone, but keep it short.  Close work changes the vision and keeps you from getting accurate tests.

Do not test your eyes when you are emotionally upset.

Do not test your eyes when you have been drinking alcoholic beverages or when you have been using recreational drugs.

Do not test your eyes when you are overworked, in poor physical condition, have bloodshot eyes or other eye diseases or are sick or in poor health.

It may be more difficult to test when you are wearing false eyelashes.

Make certain you can test at 300 feet.  You need to be able to test afterwards at 20 feet for children and young adults, but not older adults and senior citizens.

Educational/Training Sequence

The guide will first show how to test with a previous prescription and later how to test without one.

Adjusting the Frame and Mounting the Lenses

The only types of frames I can recommend are those that have the ability to adjust the PD.  Frames which do not have that ability are cheaper, and the lenses more readily fall out of the frame.  On some frames there is a single adjustment for the PD, generally between 54 and 70, and if your PD is given in two numbers, the left and the right PD, then the sum of these two numbers is used.  Other frames have separate adjustments for the left PD and the right PD.  If your PD is in a single number, just divide it by two and use that same number for the left PD and the right PD.  There are a number of other adjustments on the frame, and these must be adjusted for each individual face.  On some frames, a small screwdriver is needed to adjust the length of the temples.  Adjust the frame to fit your face and head.

The right eye is always tested first, and then the left eye.  If you are looking directly at someone wearing the frame, the left and right are turned around.  Be careful so that you are testing the desired eye.

Your lens set kit probably will come with black lenses that block all light, and frosted lenses where the light is not blocked, but you can not see clearly through the lens.  You can use either the black lens or the frosted lens to block the vision in the left eye.  Some have reported that the frosted lens works better when it is bright and you are testing outside, and the black lens works best indoors.  Block the left eye by placing the frosted or black lens in the front of the frame on the left side.

There is one slot on the back of the frame for each eye, and three in the front.  The lenses in the front can be rotated, but the lens in the back can not be easily rotated.

Look at the prescription.  The top line is for the right eye, and the left-most number is the sphere.  If that number is negative, then the corresponding lens will be found under concave sphere.  These are labeled in red in the lens set kit and the lenses have square handles with negative signs on the handles.  If the number is positive, then the corresponding lens will be found under convex sphere.  These are labeled in black on the lens set kit and the lenses have round handles with positive signs on the handles.  Pick out the desired lens from the lens set kit.  Verify that it has the correct positive or negative sign on the handle, and that the handle is square or round according to the specifications just described and that the number matches that for the sphere for the right eye.

There is still one more test to be conducted.  Verify that there are no etched lines on the lens.  If there are etched lines, then it is a cylinder lens and not a sphere lens.  Maybe the lens was misplaced in the lens set kit or maybe you took the lens from the wrong place in the lens set kit.

Take the sphere lens you just selected and place it in the slot in the back of the frame for the right eye.  If the number in the prescription for the sphere for the right eye is zero, then no lens is used at this time.

The next column over is the cylinder.  If the number is negative, then the lens will be found under concave cylinder.  These are labeled in red and the lenses have square handles with negative signs on the handles.  If the number is positive, then the lens will be found under convex cylinder.  These are labeled in black and have round handles with positive signs on the handles.  Pick out the desired lens from the lens set kit.  Verify that it has the correct positive or negative sign on the handle, and that the handle is square or round according to the specifications just described and that the number matches that for the cylinder for the right eye.

There is still one more test to be conducted.  Verify that etched lines exist on the lens.  If the etched lines are missing, then it is a sphere lens and not a cylinder lens.  Maybe the lens was misplaced in the lens set kit or maybe you took the lens from the wrong place in the lens set kit.

This lens is placed in the front of the frame, in the slot closest to the eye.  There are some etched lines on the lens.  The third column in the prescription is the axis.  An etched line must line up with the axis number.  In addition, the etched line and axis number must not be located behind the frame mounts where the numbers can not be accurately read, and it must not be located where other hardware gets in the way of reading the axis.  There are two ways to rotate the lens to achieve these objectives.  One is to rotate the lens in the slot by moving the handle.  The other way is to rotate the lens by an adjustment on the frame itself.

You want to mount the cylinder lens in such a way that the etched line is far from lens-mounting hardware, so that it is easy to rotate the lens without getting into the hardware area.  It might be necessary to flip the lens around to get a good fit.

Overview of the Testing Procedure

First a test is conducted to see if the sphere needs to be changed.  Changing the sphere changes how near-sighted or far-sighted the combination of the lenses are.  After any changes for the sphere are made, then tests are conducted to see if changes are needed for astigmatism.  After that is done, the process is repeated until it is discovered that there are no changes to make to the sphere or for the astigmatism.

REMINDER:  These instructions are for testing eyesight when you already have a prior prescription or eyeglass numbers.  A starting point is needed to use these instructions.  Separate instructions are used for getting started when you do not have a prior prescription or eyeglass numbers.  If you attempt to use these instructions without having a prior prescription, just as if the sphere and cylinder are zero, then it might work but it might not.  If you are studying these instructions for the first time, then continue here and understand what is presented here, and later you can study the instructions on how to test eyes when you do not have a prior prescription.

Testing for Changes in the Sphere

In the lens set kit, you have a -0.25 concave sphere lens.  These are labeled red and there are no etched lines on the lens.  The handle is square and has "0.25" on the handle and it has a minus sign.  Take that lens and hold it in front of the frame, in front of the eye being tested.  Do you see better with the lens, or without the lens?

In the lens set kit, you have a +0.25 convex sphere lens.  These are labeled black and there are no etched lines on the lens.  The handle is round and has "0.25" on the handle and it has a plus sign.  Take that lens and hold it in front of the frame, in front of the eye being tested.  Do you see better with the lens, or without the lens?

If you see better without the -0.25 lens and also see better without the +0.25 lens, then no changes are needed in the sphere at this time.

If you see better with the -0.25 lens and you also see better with the +0.25 lens, then something went wrong.  Test again.  You might run a test using the +/- 0.125 lens, if you have such lens, just to get an idea of where things are going.  Prescriptions are in multiples of 0.25.

If you see better with the -0.25 and worse with the +0.25, then look at the sphere lens in the back of the frame.  Using signed arithmetic (the lens in the back may be positive or negative), subtract 0.25 from the value of the lens.  Replace the sphere lens in the back with the lens that is 0.25 more negative.  Repeat this test going back to "Testing for Changes in the Sphere".

If you see better with the +0.25 and worse with the -0.25, then look at the sphere lens in the back of the frame.  Using signed arithmetic (the lens in the back may be positive or negative), add 0.25 to the value of the lens.  Replace the sphere lens in the back with the lens that is 0.25 more positive.  Repeat this test going back to "Testing for Changes in the Sphere".

If you see better with the -0.25 and it makes no difference with the +0.25, well that is interesting.  This does not usually happen.  You might test again, and if the results are the same, experiment with it by using signed arithmetic (the lens in the back may be positive or negative), subtract 0.25 from the value of the lens.  Replace the sphere lens in the back with the lens that is 0.25 more negative.  Repeat this test going back to "Testing for Changes in the Sphere".

If you see better with the +0.25 and it makes no difference with the -0.25 lens, that is interesting and does not usually happen.  You might test again, and if the results are the same, experiment with it by using signed arithmetic (the lens in the back may be positive or negative), add 0.25 to the value of the lens.  Replace the sphere lens in the back with the lens that is 0.25 more positive.  Repeat this test going back to "Testing for Changes in the Sphere".

Testing for Changes in Astigmatism

If the Cylinder is Zero on the Prescription

If the cylinder is zero on the prior prescription, that means that no astigmatism was found in the prior prescription.  Treat it as if there was no prior prescription and go to the section "Testing Eyesight when you Don't have a Prior Prescription".  When you go to that section, you know ahead of time that most likely there will be no astigmatism or else the astigmatism will not be very strong, maybe 0.25 or 0.50.  Knowing this is likely can make the testing easier and quicker.

Testing for Astigmatism Changes when the Cylinder is Not Zero

It is not good to use other approaches for testing for changes in astigmatism, other than the approach documented by testeyesight.org.  Other approaches have a high risk of getting wrong results and they do not separate astigmatism from the sphere.  Much more accurate astigmatism results are obtained by the method we advocate.  People have experienced actual harm to vision because the astigmatism was not accurate enough.  With accurate astigmatism, a better fit in glasses is found.  You are able to see clearly with single vision glasses over a wider range of distances.  Progressives work better.  In addition, as your eyesight changes, if the astigmatism is accurate, you will not need to have new glasses as often.  All these areas are covered, along with the scientific reasoning in our Conversation with ChatGPT.

Getting the astigmatism right is much more important than getting the sphere right.

It is important to keep track of the axis and the changes to the axis throughout the testing process for the eye.  Sometimes when you get closer and closer to the right lenses for the eye, it becomes more difficult to accurately determine the axis.  You want to keep track so that in case this happens, you have a reference point for the axis.  Sometimes if it is difficult to measure the axis, you can use a slightly more negative sphere to refine the axis, but once the axis has been refined, you can switch back to the accurate sphere.  Sometimes, it is necessary to take the axis from the prior prescription into account.  The one whose eyes are being tested can be encouraged to try to make abrupt changes in the axis (the rotation of the cylinder lens) to see if that works better.  Sometimes smooth changes work better.

The one area that optometrists have an advantage is that they have phoropters.  These devices allow abrupt changes in the axis to be presented to the patient, which can result in more accurate axis results.  Even with this advantage, it is still a little difficult for them to get accurate axis results.  In every situation, you can get accurate axis results with a lens set kit and frame.

A 0.25 Jackson cross cylinder is used to see if there are any changes to the strength of the cylinder lens.  In extremely rare situations where the astigmatism is very strong, the 0.50 Jackson cross cylinder could be used if the 0.25 does not work very well.

On the cylinder lens that is in the frame, there are two etched lines.  The Jackson cross cylinder has four etched lines.  Hold the Jackson cross cylinder in front of the frame, making certain that two of the etched lines on the Jackson cross cylinder line up perfectly with the etched lines on the cylinder lens in the frame.  Keeping this alignment, remove the Jackson cross cylinder and put it back.  Do you see better with the Jackson cross cylinder or without it?  Twirl the lens by twisting the handle in your fingers so that you are looking the other way through the Jackson cross cylinder.  Do you see better with twirled Jackson cross cylinder, or without it.

If you see worse both ways through the Jackson cross cylinder, then there are no changes to make to the strength of the cylinder.  Otherwise, make certain the Jackson cross cylinder is twirled in a way that the vision is sharpest.  Then look closely at the etched lines on the Jackson cross cylinder -- the two lines that are aligned with the two lines on the cylinder lens in the frame.  Those lines will either be red or silver.  The etched lines on the cylinder lens will also be red or silver.  If you are using concave cylinders, the lines will be red and the cylinders are negative.  If you are using convex cylinders, the etched lines will be silver and the cylinders are positive.  Compare the color of the two selected etched lines on the Jackson cross cylinder.  If they are the same color, then the cylinder lens needs to be stronger by 0.25.  If the cylinder is negative, then it needs to be more negative and if it is positive, then it needs to be more positive.  If the etched lines are different colors, then the cylinder lens needs to be weaker.  For example, if the cylinder is negative, then it needs to be less negative, and if it is positive, it needs to be less positive.

In most cases, the cylinder should only be changed by 0.25.  Make careful note of the axis and remove the cylinder lens and replace it with the new lens, making certain the axis is aligned.

It is necessary to refine the axis, and best results are obtained if the one whose eyes are being tested rotates the lens himself and identifies where the best vision is found.  Make certain the patient has a clear understanding of how to rotate the lens and let him do it.  Sometimes smooth changes work best, but sometimes the changes need to be abrupt to get best results.

When this is done, go back all the way to the beginning, to "Overview of the Testing Procedure".

Once there are no further changes in the sphere or the astigmatism, your work is not over yet.  The etched lines on the cylinder lenses in the lens set kit are not as accurate as I would like them to be.  Note the axis.  Remove the cylinder lens and flip it around so you are looking the opposite direction through the cylinder lens.  Align the etched lines to the axis.  Test the axis for the last time.  Take the average of the two axis, and that is the axis to use for your eyeglass numbers.

Testing Eyesight when you Don't have a Prior Prescription

Your lens set kit contains a number of concave sphere lenses and convex sphere lenses.  Test the right eye first.  Find the sphere lens which gives you the best vision for the right eye.  Your vision will still be blurry because we have not compensated for astigmatism yet.  You can try different sphere lenses.  If you have a small lens set kit, you can combine two lenses together to get the desired strength.  When you get close, you can put the lens in the back of the frame and hold a +0.25 sphere lens in front of the frame and compare with and without the +0.25 lens.  You can also do the same with a -0.25 lens.  From this, you can tell if the sphere lens in the frame needs to be replaced with a stronger or weaker lens.  The number must be a multiple of 0.25.

When you find the best sphere lens for the eye, put that lens in the back of the frame for the eye being tested.

Initial Test for Astigmatism

Make a guess how strong their astigmatism might be, based on how blurry the eye still is.  The maximum number for your estimate will be +/-6.00 and the minimum will be +/-0.25.  Divide that number by two.  This will give you a number between 0.125 and 3.00.  If the resulting number is 0.125, and your lens set kit does not have +/-0.12 cylinder lenses, then you may hold the 0.25 Jackson cross cylinder in front of the eye and rotate it instead of mounting the +/-0.12 lenses.  The Jackson cross cylinder looks like a lollypop and has the number 0.25 engraved on the handle.

Take a red-labeled concave cylinder with a square handle and a minus sign on it and having the desired strength.  Pick also a black-labeled convex cylinder with a round handle and a plus sign on the handle of the same, identical strength.  Look for tiny etched lines on the lenses.  Mount BOTH of these lenses on the front of the frame, making certain the etched lines are 90 degrees apart from each other, like cross hairs.  If the handles are completely aligned, then flip one of the lenses around so you are looking the opposite direction through the lens.  Wear the frame and rotate the lenses in the front of the frame to see where your vision is the best.  On some frames, rotation can be done by twisting a knob on the side of the frame.  On other frames such as the recommended titanium frame, a knob on the front is used to rotate the lenses.  When you rotate the lenses, make certain they maintain the 90 degree cross-hair alignment.

If you see no difference regardless of how the lenses are rotated, then either the lenses selected were too strong or too weak or else there is no astigmatism.  Repeat the test for astigmatism again, but this time use a different strength for the cylinder lenses.  If you see clearly without the cylinder lenses and there is no difference in your vision regardless of the strength of the lenses and how they are rotated, then probably you do not have astigmatism.

Sometimes better results on the axis are obtained when the axis, or how much it is rotated, is changed abruptly rather than gradually.

Best results are obtained when the one whose eyes are being tested rotates the lenses.  If someone rotates the lens for the one being tested, the results are usually inferior.

Every time you have a new axis setting, WRITE IT DOWN.  Sometimes as the vision gets sharper and sharper, it may become more difficult to get accurate axis results.  When writing it down, double-check that the etched lines are at 90 degrees from each other and look like incomplete cross hairs.  Look at the numbers that line up with the cross hairs.  The number lining up to the red etched lines will be 90 degrees different from the number lining up with the silver etched lines.  Note each of the numbers.

If you do not have +/-0.12 cylinder lenses and thus used the 0.25 Jackson cross cylinder for the test and that appears to have the best results, then you must also test using the +/-0.25 cylinder lenses and if those lenses work, then continue with those lenses.

Next, refine the sphere.  Get a convex -0.25 sphere lens and hold it in front of the frame.  Do you see better with the lens in front of the frame?  If so, then remove the sphere lens and replace it with one where 0.25 is subtracted from the sphere using signed arithmetic.  If not, then get a +0.25 sphere lens and hold it in front of the frame.  Do you see better with the lens in front of the frame?  If so, then remove the sphere lens and replace it with one where 0.25 is added to the sphere using signed arithmetic.

If the vision needs rather extreme correction, then you might need to use lenses stronger than 0.25 for the above test.

Repeat this process of checking for changes in the sphere until no changes are needed.

It might be a good idea to check the axis again, and write down any changes.

Next, use the 0.25 Jackson cross cylinder to test to see if the strength of the cylinder lenses should be stronger or weaker.  If the vision needs extreme correction, then it might be necessary to use the 0.50 Jackson cross cylinder instead, but avoid the use of the 0.50 Jackson cross cylinder if possible.

To do this, make certain the incomplete cross hairs found on the front of the frame from the cylinder lens lines up with the incomplete cross hairs found on the Jackson cross cylinder when it is held in front of the frame.  Do you see better with the Jackson cross cylinder in front of the frame?  Also try flipping the Jackson cross cylinder by twisting the handle.  Do you see better with the flipped Jackson cross cylinder in front of the frame?

If you see worse, regardless of how the 0.25 Jackson cross cylinder is flipped, and you see best without the 0.25 Jackson cross cylinder in front, then we have finished this phase of testing for the eye.  Go to Preparing Tentative Eyeglass Numbers.

If you see better in either of the flipped positions, make certain the Jackson cross cylinder is in the same flipped position where the vision was clearest.  Compare the colors of the etched lines on the Jackson cross cylinder with the colors on the frame.  If the colors line up, red with red and silver with silver, then the test needs to be conducted again but this time using 0.25 stronger cylinder lenses in the front.  If the colors do not line up, red with silver and silver with red, then we need to test again but this time using 0.25 weaker cylinder lenses in front.  Test to see if the sphere needs to be changed and then test to see if the cylinder and axis needs to be changed.  Keep testing until you get the best results.

If the colors do not line up and you already have 0.12 cylinder lenses in front (0.25 lenses if you do not have 0.12 cylinder lenses), then the test for astigmatism is over.  Go to Preparing Tentative Eyeglass Numbers.

Endless Loop Potential

When testing for astigmatism when there is no prior prescription, there is a possibility of getting into an endless loop, where a test would reveal a need for stronger cylinder lenses, and when the stronger cylinder lenses are tried, it reveals a need for weaker cylinder lenses and there is no resolution.  When this happens, just end the loop taking the average between the two cylinder strengths to be the correct value.  Ending the process to arrive at a prior prescription requires adjustment to the sphere and multiplying your cylinder value by two, so the resulting cylinder value will still be a multiple of 0.25 in the end.

Preparing Tentative Eyeglass Numbers

This section is reached when the correction in the lenses is as good as it can be when two cylinder lenses are used in front like cross-hairs.  The results are to be translated into tentative eyeglass numbers or a temporary prescription.  Although you see very well with the combination of lenses, the numbers we get will fall short of what is needed for your eyeglasses.  These numbers will be used as a starting point for additional testing.

Test both eyes and when testing, write down the sphere and the strength of the two cylinder lenses and the axis for the red etched lines and the axis for the silver etched lines for both eyes.

Using signed arithmetic, add the sphere for the right eye and the sphere for the left eye together.  The sphere refers to the lens that is in the back of the frame for the eye.  If the resulting number is negative, then we will use only red concave cylinder lenses with the square handles and a minus sign in the handle for the rest of the testing.  If the resulting number is positive, then we will  only use black convex cylinder lenses with round handles and a plus sign in the handle for the rest of the testing.

If we are using red  concave cylinder lenses, then using signed arithmetic, add the strength of the two cylinder lenses to the value of the sphere lens, and that is the new sphere value.  If we are using black convex cylinder lenses, then using signed arithmetic, subtract the strength of the two cylinder lenses from the value of the sphere lens, and that is the new sphere value.

Since we were using two cylinder lenses, multiply the strength of the cylinder lenses by two and that is the new cylinder value.  If we are using red concave cylinder lenses, then the sign will be minus.  If we are using black convex cylinder lenses, then the sign will be positive.

If  we are using red concave cylinder lenses, the axis will be the number that matched where the red etched line appeared on the front of the frame.  If we are using black concave cylinder lenses, the axis will be the number that matched where the silver etched line appeared on the front of the frame.

The result is like a prior prescription or eyeglass numbers.  Use this information and go to Overview of the Testing Procedure.

Additional testing for Reading Glasses and Progressives

If you want reading glasses or progressives, then it is important to know the reading distance.  Mount the cylinder lenses in the front of the frame and align the axis.  Using signed arithmetic, add +2.50 to the sphere and that becomes the sphere.  Do it for both the left and the right eyes.  Change the PD in the frame, and when ordering glasses.  If the PD is a single number, possibly around 62, then subtract three from that number to get the PD.  If the PD is expressed in two numbers, possibly around 31, then subtract 1.5 from the left PD and from the right PD.  This new pd is used both in the frame as well as when ordering glasses.

Wear the frame and hold some reading material in your hands.  Bring the reading material closer and further away.  Find the distance where you see the clearest.  For verification purposes, cover one eye and then the other to verify that you see the same in both eyes.  If you want your reading distance to be closer, using signed arithmetic, add 0.25 to both the left and right eye spheres and test again.  If you want your reading distance to be further away, subtract 0.25 from both the left and right eye spheres and test again.  Experiment to see which reading distance and strength of the spheres works best for you.

Using signed arithmetic, subtract the reading sphere for the right eye from the distance sphere for the right eye.  Do the same for the left eye.  The two numbers should be the same.  In your eyeglass numbers, use this number for "Near Vision Add".  That is used for progressives and bifocals.  If you want reading glasses, the spheres to use are the spheres already in the frame.  The cylinder and axis is the same as used with the distance glasses.

If you want single-vision glasses for a different distance, such as computer glasses, then the distance PD, not the reading PD is used.

Ordering Glasses

In some jurisdictions, you can not go to an optician and give them your eyeglass numbers.  They might even be forbidden by law to provide glasses without a prescription from an eye professional, and they might even check on-line to verify that the prescription comes from a licensed eye professional.  You can, however, order your glasses on-line.  If you order from zennioptical.com, you might get better results if you do not request an expedited order.

Contact us today.