Goldmann Tonometer Remains Gold Standard for Measuring IOP

Goldmann Tonometer Remains Gold Standard for Measuring IOP

Most new technologies for measuring intraocular pressure (IOP) fail to measure up to the Goldmann applanation tonometer, according to Yvonne Buys, MD, FRCSC. She presented a review of currently available devices at Saturday’s Glaucoma Subspecialty Day.

“We do have a variety of technologies available outside of the Goldmann. Each has its own strengths and weaknesses, said Dr. Buys.  

New devices have pros and cons. Most of the new devices can detect very high IOP, she noted. But clinicians are often interested in the lower IOPs as well, which are best detected with the Goldmann tonometer. So, despite the Goldmann’s limitations—it’s nonportable, requires sterilization, and needs to be calibrated—it remains the gold standard for IOP measurement.

Key properties of new tonometry instruments:

• PASCAL: Based on the principle of contour matching rather than applanation, this approach eliminates influence of corneal thickness, rigidity, curvature, and elastic properties.
• Reichert ORA and Corvis STL: These devices employ noncontact, bidirectional, air-puff applanation and provide a corneal-compensated IOP measurement.
• Diaton: Portable and handheld, the Diaton does not require sterilization or anesthesia. Because it measures IOP through the eyelid over the sclera, it is not affected by central corneal thickness or corneal rigidity.
• Icare: The Icare is portable, does not require sterilization or anesthesia, and can be used at home. The contact time is exceptionally brief and can pick up transient dips or spikes in IOP; to overcome this variability, the user must take the average of 4 out of 6 readings. The device records IOP, time, and date and calculates a quality score using an algorithm. The data are stored in the device and can be accessed later by the physician.
• Triggerfish: This device consists of a contact lens sensor, plus a small antenna near the eye that transmits data wirelessly. It can be used at home and offers continuous measurement. For example, 24-hour IOP patterns can be monitored continuously without having to wake the patient.

Lack of correlation between devices. The bottom line, Dr. Buys said, is that the correlation between the technologies is poor. Most new technologies either over- or underestimate IOP relative to the Goldmann. “So the main point is not to change techniques when you’re following an individual patient,” she said.—Anni Griswold

Financial disclosures. Sensimed: S.

Disclosure key. C = Consultant/Advisor; E = Employee; L = Speakers bureau; O = Equity owner; P = Patents/Royalty; S = Grant support.