Using Thomson Test charts for remote testing

Current guidelines on Social Distancing have made it difficult (or impossible) for patients to attend a clinic to have their visual acuity checked.

The good news is that the Thomson Test Chart may be used in association with video-conferencing software (e.g. Zoom or Teams) to assess the vision of patients in their homes or other remote locations.

Outline instructions:

  • Create a meeting and send the patient a meeting invitation link.
  • Add the patient to the meeting when they log in. You can then welcome them and explain the procedure by video link.
  • Run the Thomson Test Chart software on your computer and select Share screen in the video-conferencing app
  • Select OptionsScreen calibration within the Test Chart software. This will display a large letter E on the patient’s screen which they should measure on their screen using a ruler. You then enter this value into the Test Chart software along with the longest viewing distance that they can achieve from their computer (e.g. 250 cm). The letter size will then be correctly calibrated for the patient’s screen size and viewing distance.
  • The patient then stands (or sits) at the required distance from their screen while you display an appropriate test chart. The patient can be given appropriate instructions and encouragement via the videolink while you can monitor that they are following those instructions.

Trials have shown that the accuracy and test/retest repeatability of this approach is similar to that for measurements taken in the clinic.

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