Welcome to Test Eyesight

Welcome to dr.TestEyesight.org

This web site was originally created to assist eye professionals when they test eyesight using a lens set kit and frame, and they do not have access to other equipment and they do not have a prior prescription. It was designed not to state anything that ran contrary to the practices of the eye professions and not to offend.

After this web site was built, a vastly superior way to test eyesight when the prior prescription is not available was developed using a lens set kit and frame and a 0.25 Jackson cross cylinder and sometimes a 0.50 Jackson cross cylinder. That site is https://testeyesight.org

Unlike this site as originally constructed, https://testeyesight.org includes content that recommends rather strongly some improvements that need to be made with the process of testing eyes. Some eye professionals, being unwilling or unable to consider the need for improvements, might be offended by https://testeyesight.org.

The earlier version of dr.testeyesight.org follows, and may be useful to eye professionals who do not want to follow the procedures found in https://testeyesight.org

https://testeyesight.org also shows better ways to test eyesight when you have access to the prior prescription.

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This web site, dr.Testeyesight.org, was designed and written by a layman, but it is intended for optometrists to use as a valuable tool for testing eyesight when the only equipment you have is a lens set kit, frame and pd ruler and you do not have access to their previous prescription for eyeglasses.

Before using the lens set kit and frame, it is very helpful to know as accurately as practical, what prescription will be eventually needed. Optometrists in America obtain this information by looking at prior prescriptions, measuring the prescriptions on the patient's latest glasses, and by taking images of the eye.

There are situations where this helpful information simply is not available, and you must test the eyesight without that information. You already know how to do it, but this web site makes the work much easier and quicker.

You may find yourself in that situation if you are in another country, and the equipment that is common in America is not available or affordable where you are. You might be doing mission work in America or elsewhere and you might not have access to all your equipment. You might want to take your lens set kit and frame to retirement homes or nursing homes, and you could not take all your equipment with you. Some people can not leave their houses because of health and mobility reasons, and you could take the lens set kit and frame with you to help with their needs.

How does this web site help you? Testeyesight.org provides tables and links to tables and does the math for you. When you change the strength of the cylinder, the sphere also changes with it. These tables give you a list of cylinder and sphere choices which maintain the same combined near-sightedness or far-sightedness so that you do not need to do the math between each astigmatism test.

If you have a small lens set kit, you might still be able to use it. 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 is the same for both lenses.

To start, use only the sphere lenses, not the cylinder lenses at this time. The right eye is tested first. The sphere lens or combination of lenses is found which gives the sharpest vision for the right eye. Then the left eye is tested. The sphere for the right eye and the left eye are added together. If the sum of the two is positive, then only positive, convex cylinders will be used and negative concave cylinders will never be used for this individual. If the sum of the two is negative, then only negative, concave cylinders will be used and positive convex cylinders will never be used for this individual. If the sum is zero, either concave or convex cylinders can be used, one or the other, but not both. The reason for doing this is to keep the thickness of the lenses when testing down to a minimum. More accurate results can be obtained that way.

Now you are ready to use the table. Read the instructions and then click here. Instructions: A list of spheres will appear. Click on the number for the sphere. A list of cylinders will appear. Click on zero for the cylinder. A list of sphere and cylinder combinations will appear. Try different sphere and cylinder combinations to see what gives the sharpest vision. Don't forget to test different axis at the same time.

Sometimes, but not always, the sharper the vision gets with the lenses, the more difficult it is to get accurate axis measurements. Keep track of the axis, in case this happens.

Keep in mind that the axis markings on the cylinder lenses are not as accurate as I would like them to be. To get more accurate axis measurements, flip the cylinder lens over so the patient is looking through the lens in the other direction and then measure the axis. The final axis would be the average of the two.

Next, refine the sphere. Put the sphere and cylinder in the frame and adjust the axis. Try holding different sphere lenses in front of the frame and see which lens gives the sharpest vision. Add the sphere numbers together and that becomes the new sphere to use. Go to the table again, this time clicking on the new sphere and clicking on the cylinder, which you just determined. Again, you will come up with a list of spheres and cylinders to try.

Keep testing and using the tables until you get something close to the best results possible. The idea is to use the links and tables to get as close as possible to the ideal prescription, and not necessarily exact. Once you have gotten the prescription as close as you possibly can, then you can follow your standard procedure to test the eyes and get the best results, and you won't need the tables to do that.

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