Although there are several different types of tonometers, they all operate with the common goal of helping eye care professionals measure the intraocular pressure (IOP) on the interior of a patient’s eye. The IOP measurement helps optometrists and ophthalmologists determine a patient’s risk for developing glaucoma.

Glaucoma is the leading cause of blindness in people over the age of 60 and is caused by an increased amount of fluid pressure within the patient’s eye. This increased pressure can damage the patient’s optic nerve.

Because glaucoma can eventually cause blindness if it goes untreated, a tonometry test is a vital part of the examination for detecting changes in the eye as early as possible. The actual type of tonometer used will depend on the patient and the physician’s preference. Continue reading to learn more about the different types of tonometers.

Digital contact tonometers

The Keeler Digital Applanation Tonometer (D-KAT) is a digital version of our popular KAT applanation tonometer. The Digital Applanation Tonometer is a ‘GAT’ and operates based on the Goldmann method, which means it measures IOP from the force required to flatten a consistent area of the patient’s cornea.
This device offers users exceptional reliability and ease of use. It features an LED display and internal electronics that allows for the accurate and fast measurement of IOP. To further simplify the procedure, the D-KAT has an illuminated display that facilitates easy readings, even in the darkest of examination rooms.
The D-Kat is available in both Take-away as well as Fixed variants and is compatible with most slit lamps including Keeler’s. Because the D-KAT will come into contact with patients’ corneas, you should consider the Keeler Disposable Applanation Prisms.

Standard mechanical contact tonometers

Our standard mechanical contact tonometers are also based on the Goldmann applanation tonometry (GAT) method, which is the most common and recognized as the international gold standard for measuring IOP. This method involves using a tonometer tip to touch an anesthetized cornea to discover the amount of force required to flatten the cornea.

During this procedure, the eye care professional will turn the tension knob altering the corneal force. The IOP will be determined when the internal aspects of the two semicircles contact each other. The standard contact tonometer does come into contact with patients’ eyes, so should consider the Keeler Disposable Applanation Prisms.

Perkins Hand-Held Tonometer

Similar to the standard contact tonometer, the Perkins tonometer utilizes the same applanation prisms. However, the Perkins tonometer is portable and can be used for patients who:

  • Are being tested in the supine position
  • Have physical limitations that prevent them from positioning in a slit lamp
  • Aren’t being tested in the office with a slit lamp

Non-Contact Tonometer (NCT)

Non-contact tonometer or a pneumotonometer involves applying a quick puff of air pressure to the patient’s eye through an instrument. The quick puff of air flattens the patient’s cornea in a non-invasive way, which means the eyes do not have to be numbed before the test.

The force required to flatten the patient’s eye is detected by sensors to determine the patient’s IOP. In the event the patient has abnormal results, the physician should perform other tests to confirm the diagnosis. These devices have increased in accuracy to the Goldmann applanation tonometry (GAT) and in most countries you must prove accuracy to Goldmann prior to receiving marketing clearance (FDA). Keeler offers both a desktop and mobile non-contact tonometers.

The AccuPen

The AccuPen is a handheld electronic device that is shaped like a large marker. It utilises a tiny plunger to determine the amount of resistance given by an anesthetized cornea when contacted. Gravity Offset Technology provides precise IOP measurements with less calibration compared to other handheld tonometers. Micro strain gauge technology combined with proprietary algorithms provide reproducible results.

The AccuPen can be easily transported and offers the most advantages when used on a patient’s edematous or scarred cornea.

Rebound Tonometer

Rebound tonometry assumes that patients with a higher IOP or those with harder eyes will induce a faster deceleration of a probe than patients with a low IOP or softer eye. A rebound tonometer measures the induction current generated when the metal probe bounces or rebounds off of the cornea back to the device.

The velocity of the rebound is converted into mm HG. The method of rebound tonometry doesn’t require anesthesia and can measure IOP relatively quickly.

Contact Keeler

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