Eye Exam Chart or Snellen Chart? 5 Official Names for Eye Exam Tools

Whenever you go to get your eyes examined, you’re used to seeing a few different pieces of equipment that help you and your eye care professional figure out information about your eye health and whether or not you’ll be needing a new prescription.

Most of these machines and devices you see are fairly commonplace at this point in your life, but their true names may not be.

Here’s a short lesson on some of the different tools your eye doctor uses during an exam that you are familiar with, along with the real name of said tools.

1. Snellen Chart – Eye Chart

Remember being a kid and being forced to look at the stereotypical chart on your eye doctor’s wall, with the big “E” printed at the top? That eye chart you’re so used to actually goes by a different name, known as the Snellen Chart. It was developed in the 1860s, making it a rather old but useful piece of equipment.

2. Tonometer – Eye Puff Machine

The “eye puff machine” that comes toward the beginning of an eye exam actually goes by the name tonometer, which actually encompasses a few different categories of machine.

The purpose of the tonometer (or eye puff machine) is to detect the pressure in the eyes, which is an indicator of glaucoma. The eye puff machine uses, as its common name suggests, a puff of air to detect the pressure. Tonometry (as a general name for the procedure) detects pressure in a variety of ways, but the machine we are most familiar with uses the air puff as it’s non-invasive and quick to do.

3. Phoropter – Refractor

“One, or two,” your doctor asks, signaling that they are using the phoropter on you. This machine is better known as the refractor, where your eye doctor will flip between different lenses and attempt to find the specifics of your prescription so that your eyes can see at their best. This is known as the refraction process, which is why we are familiar with the term “refractor” rather than “phoropter” for this procedure.

4. Ishihara Test – Colorblind Test

When you were a young child, you probably have some memory of going in with your eye doctor to look at colorful circles that had numbers printed within them. The numbers would be in a green or red, while the surrounding circles would be the opposite color of the numbers.

This exam was done to determine colorblindness of different varieties, and the technical name for this exam is the Ishihara test. This test only encompasses red-green colorblindness, but there are other varieties of these exams that detect colorblindness of different types.

5. Keratometer – Ophthalmometer

This instrument doesn’t have as “common” a name as the others listed, but it’s still an integral part of the eye exam, particularly for those who may have astigmatism.

This machine, technically known as the keratometer, is useful in detecting curvatures on the cornea that may be a result of astigmatism. The machine measures this during an eye exam and gives the physician the information necessary to decide whether or not the astigmatism exists, and if it does, it can help determine the way in which the cornea is misshapen.