In part 1 of this blog series on how Visibly’s prescription renewal test works we shared how color vision can be tested digitally. Today, we’re going to explore the next part of our test, visual acuity.
What is visual acuity? It’s the measurement of how well a patient can see at a certain distance and is typically reported on a 20/20 scale. The results are just one component of a patient’s vision.
During an eye doctor’s visit, visual acuity is measured using either a Snellen eye chart, which features a large E at the top followed by rows of alternating letters, or a tumbling E chart, which has a series of E’s on each row facing different directions. With both charts, the doctor will ask a patient to cover one eye at a time and read a few different lines off the chart from a certain distance. The responses allow the doctor to understand a patient's 20/20 vision measurement.
In the Visibly test, patients are asked to move ten feet away from their computer screen with their smartphone in hand. The test will help the patient measure this distance by asking them their shoe size and calculating how many steps they should take away from their computer screen. Once the patient is ten feet away from their screen, the visual acuity assessment will begin by showing a letter E facing either up, down, right or left. They will be instructed to choose the direction they see the E facing on the screen from the options available on their smartphone.
If the patient doesn't have a computer, they can complete the test with just a smartphone. The experience is the same except the patient will be ten feet from their smartphone and use voice commands to indicate what they are seeing on the screen.
This process is repeated about 8-12 times per eye depending on the patient. The responses are then measured and determined on a 20/20 scale.
Want to renew your vision prescription at home? Create an account with Visibly and start your test today.