The eye pressure, also called the intraocular pressure (IOP), is measured at all comprehensive eye exams to screen for glaucoma. In glaucoma, the eye pressure is higher than normal and it results in the loss of vision. There are different methods for measuring the eye pressure and each has unique benefits and challenges. The most common methods of checking the eye pressure include Goldmann applanation tonometry, non-contact tonometry (air puff), and by palpation of the eyeball.
Why the Eye Pressure is Important
The eye pressure is the only risk factor for glaucoma which can be modified, meaning it is the only way to identify or treat anyone with glaucoma.
Since glaucoma does not cause any symptoms in the early stages of the disease, it must be detected at a routine eye examination by measuring the eye pressure.
In addition to glaucoma, other conditions such as eye inflammation, wounds, or even tumors can be identified by reading an abnormal eye pressure.
Goldmann Applanation Tonometry
The method of checking the eye pressure which is considered the gold standard is Goldmann applanation tonometry.
This method requires the use of a numbing eye drop and yellow dye called fluorescein dye.
After the numbing drop and yellow dye are put into the eye, the doctor will use a small device attached to a microscope to softly touch against the front of the eye and record the eye pressure.
This method is beneficial in that the reading is very precise and accurate which is why it is the gold standard and used on all known glaucoma patients or high risk glaucoma suspects.
However, the disadvantages of Goldmann applanation tonometry are the need for eye drops and that it can cause apprehension from the patient when the tonometer probe begins to approach the eye.
Non-Contact Tonometry (Air Puff)
Another method of checking the eye pressure which has become very common is using a non-contact tonometer or what is known as the air puff test.
Instead of using a device to touch the eye, the non-contact tonometer uses a puff of air to evaluate the eye pressure.
For non-contact tonometry, the instrument will be on a table and have a chin rest and forehead rest, once the patient is positioned, the instrument will puff a small amount of air against the eye and record the eye pressure based on the resistance.
This method is very fast and easy to perform on many patients. It does not require any eye drops and has no contact of any form with the eye.
However, this test is notoriously bothersome for patients who are sensitive to the air puff and may give poor results if the patient is unable to cooperate well.
Manual Palpation for Eye Pressure
In infants and small children, other precise methods of measuring the eye pressure are unable to be performed.
The best method of measuring the eye pressure in these small children is using manual palpation.
This allows the doctor to simply press against the closed eyelids to ensure that both are soft and equal in pressure.