For Testing at 4 Meters (13 Feet).
Much like Patti Pics optotypes, PV Number optotypes follow a Sloan standard. Not only do PV Numbers adhere to the Sloan 5×5 grid, but the numbers have been chosen specifically for their difficulty level. PV Numbers also have an equal blur at the threshold. By following a constant standard for each charts recordings are more accurate and reliable. Also, each test will have the same results no matter if it uses Sloan, PV Numbers, or Patti Pics optotypes.