January, 2020- Taking Tonometry Into the 21st Century

January Issue, 2020


New prism is 94% more accurate than the legacy method.

The CATS prism, which received 510(k) clearance in March 2018, fits onto any existing Goldmann or Perkins tonometer without need for recalibration or alteration in measurement technique or interpretation.

Designed to overcome IOP measurement errors due to patient variability in corneal thickness, rigidity, curvature, and tear film adhesion force, the CATS prism differs from a standard GAT prism by its shaped contact surface, which has a central concave region surrounded by an annular convexity.

“…The prism was designed to significantly decrease patient IOP dependence on corneal biomechanical and tear-film properties, which is the primary source of individual error….”

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The CATS Tonometer Prism™ is the first innovation in applanation prism technology in 60 years.
Rigorous and consistently repeatable clinical tests have proven that the CATS Tonometer Prism™ brings significantly more accuracy to Intraocular Pressure (IOP) measurements than the legacy Goldmann Applanation Tonometer (GAT) IOP prisms.

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Journal of Ophthalmology December 2019 – Modified Goldmann prism intraocular pressure measurement accuracy and correlation to corneal biomechanical metrics: multicentre randomized clinical trial. Clinically evaluate intraocular pressure (IOP) measurements taken with a Goldmann applanation tonometer (GAT) prism and a modified surface Goldmann prism examining measurement differences correlated to central corneal thickness (CCT) and corneal hysteresis (CH) values.

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Each issue we will take a look at some of the most frequently asked questions that we receive and feature a Q & A below!

Q: When the clinician uses the CATS prism, does s/he still need to perform CCT and CH (hysteresis) error correction?

A: Usually No. CATS measures “true” IOP to within +/-2mmHg in 97% of the population. However, in cases of extremely abnormal corneas or those with corneal pathological conditions, the clinician should consider performing CCT and CH to gather additional data and insights into the condition.