• Ensure the patient does not have allergies to latex or anaesthetic before putting on a new sterile cover on the tono-pen transducer and apply anaesthetic drops
  • For the first measurement of the day you should calibrate the tono-pen
    • Turn on the tono-pen, then press the user button twice rapidly to enter calibration mode (Many models will have an LED display reading "CAL")
    • Then point the transducer straight down
    • After 15 second you will hear a audible beep, at which you point the transducer straight up
    • A functional tono-pen will then beep once more (Many models will have an LED display reading "GOOD")
    • Press the operator button once if you are ready to take measurements.
  • Once the tono-pen is calibrated or if this is a repeat measurement, you are ready to begin
    • Press the user button once, the tono-pen should beep and the first measurement is ready to be taken
    • Brace the patients eyelids open with one hand, telling the patient to look straight ahead
    • Hold the pen with your other hand like a pencil and brace this hand against the patient's maxillar region for stability
    • Tap the corneal surface lightly four time to get a reading with the statistical reliability (two beeps will be heard after a statistical reading is made)
      • Indentation of the cornea is not required and may lead to inaccurate readings


  1. Bickley LS, Szilagyi PG. Bates' Guide to Physical Examination and History-Taking, 11th ed. Baltimore: Lippincott Williams & Wilkins; 2011.
  2. Cline, MC, Ma, JM, Cydulka, RK, Meckler, GD, Handel, DS, and Thomas, SH. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed. New York: McGraw-Hill Professional; 2010.
  3. Hay, WW, Levin, MJ, Deterding, RR, and Abzug, MJ. Current Diagnosis and Treatment: Pediatrics, 22nd ed. New York: McGraw-Hill Professional; 2014.
  4. Leblond, R.F., Brown, D.D., and DeGowin, R.L. DeGowin’s Diagnostic Examination, 9th ed. New York: McGraw-Hill Professional; 2008.
  5. McDonnell, C. Assessment of the anterior chamber angle and depth. (accessed 24 December 2014).