Clinical Pearls

We use the tonopen under a few conditions

• The patient keeps blinking or flinching upon trying to perform applanation

• The patient has an infection (conjunctivitis/HSV keratitis). The tonopen has a disposable latex tip so is more hygienic in this respect

• The patient has mobility issues and they cannot position their head on the slit lamp for applanation (especially with wheelchair patients )

Tips for using the tonopen: 

• Do not be afraid to place your hand on the patient's face for support while using the tonopen and avoid holding the tonopen freely in the air ("hover- handing"). This will eliminate involuntary movements and decrease the risk of a corneal abrasion. 

• Be sure to lightly "tap" on the cornea, and not just press in and out. 

• Please wear gloves when doing this

• This is what the reading looks like with an IOP of 21 mmHg

• Notice the bar over the 5% marking

• This means that the reading has less than 5% error (the best quality)

• If you notice it is over the 10/20/>20, try to redo it for a more accurate reading!