Verify the Calibration of your Visual Acuity Charts

To ensure that your visual acuity (VA) charts are correctly calibrated, you should measure the height of a letter corresponding to 6/60 Snellen (meters) (which is equivalent to 0.10 Decimal, 20/200 Snellen (feet), or 1.00 logMAR). Additionally, measure the viewing distance from the chart to the patient’s eyes in millimetres.

Next, fill in the form below with these measurements, and you will instantly receive an email with the calculation of any error in the VA values that your charts might be displaying.

If desired, you can repeat this process with other VA sizes (for instance, 6/12 Snellen (meters) or 20/40 Snellen (feet)) to confirm the accuracy of your calibration.