How to Measure Intraocular Pressure

Intraocular pressure refers to the fluid pressure in the eye. Eye-care professionals, optometrists and ophthalmologists, use a tonometer to measure a patient's intraocular pressure. When this is higher than normal, ocular hypertension occurs, which can be a precursor to an eye disease called glaucoma or a gradual loss of vision. Elevated intraocular pressure may also be caused by medication, inflammation of the eyes, physical exertion and other factors.

Things You'll Need

• Tonometer
• Fluorescein
• Local anesthetic drops
• Applanation prism
• Gauze swabs
• 70 percent Isopropyl alcohol

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Instructions

Instructions

• 1

  Prepare the equipment used for measuring intraocular pressure. You want to make sure that the prism is properly disinfected with sterile water and isopropyl alcohol. The measuring prism's graduation should also be set to '0' and aligned with the white marked point on the head of the tonometer. The tonometer should also be calibrated at 10mmHg.

• 2

  Prepare the patient for measurement. The patient should sit at the slit lamp that is adjusted to a comfortable height. The chin and forehead should be placed on the rest and headband respectively. The magnification of the slit lamp should be set to x 10.

• 3

  Administer local anesthetic and fluorescein. Before measuring intraocular pressure, you need to administer anesthetic to numb the eye and a small amount of fluorescein on each eye. Fluorescein is a dyeing agent to detect blood stains in the eye.

• 4

  Measure IOP. For this you want to make sure that the slit beam shines on the tonometer head from the right side of the patient to measure the IOP for the right eye. The same rule applies for the other eye. It is also important to move the filter so that a blue beam comes out from the blue filter. You want the light beam to be wide so you can easily find the fluorescein rings.

• 5

  Note the reading from the tonometer dial. To accurately measure the intraocular pressure, you want to slowly move the tonometer forward so that the prism is gently touching the center of one cornea. Turn the calibrated dial clockwise to get the two fluorescein semi-circles meet and form a letter S.

• 6

  Remove the prism from the surface of the cornea. Make sure to wipe the tip of the prism after use and then repeat the same process for the other eye.

• 7

  Read the tonometry rings to verify IOP. You will see the first image below before you reach the endpoint of the calibration when IOP is high. Turn the calibrated dial clockwise to adjust and get the right reading.
  On the other hand, intraocular pressure is low when you find the second image. For this, you want to turn the calibrated dial counter-clockwise to get the right endpoint.
  Finally, a correct reading will result in to the third image.