Corneal Hysteresis and IOPcc

What is Corneal Hysteresis?

Corneal Hysteresis (CH) is an assessment of the cornea’s ability to absorb and dissipate energy and has been shown to be independently predictive of visual field progression in glaucoma. Different from thickness or topography, which are geometrical attributes, Corneal Hysteresis is a tissue property.

Make a more confident glaucoma risk assessment, with Corneal Hysteresis. Only Ocular Response Analyzer® G3 from Reichert® measures Corneal Hysteresis (CH), a superior predictor of glaucoma progression, which is more associated with visual field progression than CCT or IOP.1,3,5 Ocular Response Analyzer helps add clarity to your glaucoma decision making process. CPT Code 92145, was published for the Corneal Hysteresis measurement provided by Ocular Response Analyzer.

Corneal Hysteresis Insights: ‘The Ophthalmologist’ Advanced Glaucoma Technologies Forum

Insights on the role of Corneal Hysteresis in Glaucoma management.

Taken from the Advanced Glaucoma Technologies Forum presented by The Ophthalmologist

“Hysteresis is a very powerful risk factor for progression of the disease, and I think it’s one that’s largely overlooked. In fact, if you take Hysteresis out of the central corneal thickness measurement, central corneal thickness might not even be a risk factor for glaucoma progression. Hysteresis is absolutely critical for estimating the risk.” – Robert Weinreb, MD.
Glaucoma opinion leaders Ike Ahmed, MD, E. Randy Craven, MD, Constance Okeke, MD, Inder Paul Singh, MD, and Robert Weinreb, MD, discuss the strides made in detection and management of glaucoma, and explain the benefits of measuring Corneal Hysteresis for glaucoma risk assessment. In this round table discussion, the doctors explain how Corneal Hysteresis aids them in better predicting glaucoma progression.

“Things like Hysteresis have helped me a great deal because it does give you an understanding of the quality of the IOP. In other words if someone has a low hysteresis with a high pressure I’m much more worried than having a high Hysteresis with a high pressure,” explains Dr. Singh.

Significance of Corneal Hysteresis in predicting glaucoma development, in 25 seconds with Felipe Medeiros, MD.

Felipe Medeiros, MD briefly describes the relevance of his new publication: A Prospective Longitudinal Study to Investigate Corneal Hysteresis as a Risk Factor for Predicting Development of Glaucoma. Corneal Hysteresis was found to be independently more predictive of conversion to glaucoma than other risk factors, including IOP and CCT.


IOP Values Derived from Reichert® Ocular Response Analyzer® G3 Strongly Correlate to Goldmann IOP

David Lunt, Consultant Ophthalmic Surgeon from Leeds Hospital in England, describes the findings from his study investigating the accuracy and clinical utility of the Reichert Ocular Response Analyzer® G3 compared to Goldmann Applanation Tonometry. IOP readings from the Ocular Response Analyzer G3 were shown to correlate strongly with Goldmann, is subject to less inter-operator variability, is less challenging to use, offers reduced risk of infection transmission, and does not require topical anesthesia. Using Ocular Response Analyzer G3 for IOP measurements could offer an invaluable solution for seeing an ever increasing number of patients safely and effectively, especially in virtual glaucoma clinic.


Eyes on Glaucoma: Corneal Hysteresis/IOPcc, Glaucoma Vital Signs You May Be Missing, N Radcliffe, MD

Nathan Radcliffe, MD, discusses how in recent years our understanding of the cornea’s role in glaucoma has evolved substantially. We now know that the cornea itself provides us with independent information, and properties such as corneal hysteresis are now considered to be essential in glaucoma risk assessment. In addition, corneal biomechanical properties influence tonometer accuracy more than corneal thickness alone - and modern tonometry methodologies are capable of overcoming these complex variables.


How is Corneal Hysteresis useful in glaucoma decision making, J. Thimons, OD.

Dr. James Thimons, OD, discusses the use of the Ocular Response Analyzer and the importance of its Corneal Hysteresis and IOPcc measurements in the monitoring, diagnosis, and treatment of glaucoma. Here learn what Corneal Hysteresis is, why it is an essential glaucoma risk factor, and how to incorporate this measurement into daily clinical practice. In addition, Dr. Thimons explains why corneal biomechanics influence IOP measurement accuracy and how the IOPcc measurement provides a better assessment of the true intraocular pressure. 


Ocular Response Analyzer® in clinical practice, use and interpretation, Nathan Radcliffe, MD

Nathan Radcliffe, MD, demonstrates use of the Ocular Response Analyzer®, describes the measurement results, and discusses how the Corneal Hysteresis and IOPcc measurements impact glaucoma decision making. He also discusses delegation of the test to technicians, patient flow, and other practical issues in this informative video.


Corneal Hysteresis and glaucoma patient management, Davinder S. Grover, MD, MPH

Davinder S. Grover, MD, MPH, speaks about Corneal Hysteresis (CH) as an assessment of the cornea's ability to absorb and dissipate energy, which is different from thickness or topography, which are geometrical attributes of the cornea. Corneal Hysteresis is independently predictive of visual field progression in glaucoma.

Will Your Patient Progress? Stratifying Glaucoma Risk with Corneal Hysteresis - Webinar

Distinguished speakers Davinder S. Grover, MD, MPH, and Paul M. Karpecki, OD, FAAO, discuss and review evidence and cases supporting Corneal Hysteresis and Corneal Compensated IOP (IOPcc) as essential risk factors for glaucoma decision making.


Corneal Hysteresis: Clinical Relevance in Glaucoma in 90 Seconds, N. Radcliffe, MD

Nathan Radcliffe, MD and Christopher Starr, MD, both of Weill Cornell Medical College, New York-Presbyterian Hospital, discuss the clinical applications in glaucoma of Corneal Hysteresis (CH) and why Ocular Response Analyzer® should be brought into routine glaucoma management.

The Role of Corneal Hysteresis in Glaucoma Progression, Felipe Medeiros, MD

Felipe Medeiros, MD, Professor at Duke Ophthalmology, describes his recent study using Corneal Hysteresis (CH) — a measure of the eye’s viscoelastic biomechanics properties — for predicting glaucoma progression. Dr. Medeiros explains the importance of collecting Corneal Hysteresis measurements to better determine patients at high risk for glaucoma.

Corneal Hysteresis (CH): An indispensable tool in the glaucoma decision making process.

Corneal Hysteresis has consistently shown to be predictive of, or strongly associated with, glaucoma progression, and more powerfully so, than key indicators such as IOP and CCT, making it an indispensable tool in the glaucoma decision making process.

Glaucoma is the second leading cause of irreversible blindness in the world. Despite the fact that there are a variety of well-known risk factors, it can be difficult to diagnose. Beyond diagnosing, predicting an individual patient’s rate of future glaucoma progression is often extremely challenging for clinicians.

The Ocular Hypertension Treatment Study (OHTS), and similar studies, have brought to light the relevance of central corneal thickness (CCT) in glaucoma. Numerous studies utilizing the Ocular Response Analyzer have confirmed the importance of the cornea in glaucoma decision making and, in fact, demonstrated that Corneal Hysteresis is of far greater significance than CCT.

Corneal Compensated IOP (IOPcc): Less affected by corneal properties. 

Ocular Response Analyzer takes corneal biomechanical properties into consideration, providing Corneal Compensated IOP (IOPcc). The patented bi-directional applanation system enables the measurement of Corneal Hysteresis and IOPcc.

Intraocular pressure (IOP) is the only modifiable risk factor for glaucoma. As such, accurate measurement of IOP is critical for proper diagnosis and management. However, it is widely recognized that Goldmann and other tonometers are influenced by corneal properties. While corneal thickness has been accepted as an important factor contributing to the accuracy of IOP measurements, it has been shown that attempting to adjust IOP values by means of a corneal thickness correction formula does not add any value to the glaucoma decision making process. It is biomechanics, not thickness, that predominantly influence the accuracy of IOP measurements.

Corneal biomechanical properties can affect the accuracy of measured IOP values by as much as 17 mmHg in normal eyes3 and more than 20 mmHg in eyes with corneal pathology.4 IOPcc effectively eliminates these influences on the pressure measurement.

Compensated IOP (IOPcc) - A pressure measurement that is less affected by the cornea than other methods of tonometry. IOPcc is patented technology, exclusive to Reichert. 
- IOPcc is less affected by corneal properties than Goldmann2
- IOPcc is a better indicator of glaucomatous damage than Goldmann tonometry6

How is Corneal Hysteresis measured?

Corneal Hysteresis is the difference in the inward and outward pressure values obtained during the patented dynamic bi-directional applanation process utilized by the Ocular Response Analyzer. It is a characterization of the cornea’s ability to absorb and dissipate energy, which is a function of visco-elastic biomechanical properties of the cornea.


CPT® Code 92145 published for Corneal Hysteresis.

A new CPT code, 92145, has been published specifically for the Corneal Hysteresis measurement provided by the Reichert® Ocular Response Analyzer®. In the 2015 CPT handbook, a new, permanent, Category I CPT code, 92145 (Corneal hysteresis determination, by air impulse stimulation, unilateral or bilateral, with interpretation and report), replaces the prior temporary, Category III CPT code, 0181T. The new code took effect January 1, 2015. For more information regarding CPT Code 92145, please consult your medical billing specialist.

Designed and Assembled in the USA.

Ocular Response Analyzer G3 was invented, designed, and is proudly engineered and assembled in the USA at our state-of-the-art world headquarters in Buffalo, New York.

Decades of Glaucoma Care Innovation.

In 1959 Dr. Bernard “Bernie” Grolman flipped on the radio during his morning commute to American Optical, now Reichert Technologies, and heard a public service announcement about the prevalence of glaucoma. Being familiar with tonometry due to his industry experience he thought, “What if I could create an instrument that eye doctors could use to help diagnose a leading cause of blindness, without touching the cornea?”

“The need for a non-contact tonometer was so obvious,” said Grolman, who would spend the next 10 years of his life designing and testing the original AO Non-Contact Tonometer.

Using an air pulse with electro-optical detection to provide Goldmann-like measurements, the non-contact tonometer enabled user-friendly measurement of IOP without the need for topical anesthesia or corneal contact.

Unveiled in 1971, the NCT I was the buzz of the entire industry. American Optical, now Reichert Technologies, continued to innovate on the concept, introducing generation after generation of non-contact tonometer.

Fast forward to 2001 when David Luce, Ph.D. discovered that, using the same basic measurement process, information about corneal biomechanics could be extracted from the NCT measurement signal. The Corneal Hysteresis measurement was born and the instrument that became known as the Ocular Response Analyzer was made available for sale in 2005. At long last, the topic of corneal biomechanics moved out of the laboratory and into the clinic, spawning entire new sections on conference programs and launching the subject to the forefront of the ophthalmic publication landscape.

Reichert remains the world-leader in tonometry products and has become the pioneering innovator behind Corneal Hysteresis.


1 - Medeiros FA, Meira-Freitas D, Lisboa R, Kuang TM, Zangwill LM, Weinreb RN. Corneal hysteresis as a risk factor for glaucoma progression: a prospective longitudinal study. Ophthalmology. 2013 Aug;120(8):1533-40.
2 - Felipe A. Medeiros, MD and Robert N. Weinreb, MD. Evaluation of the Influence of Corneal Biomechanical Properties on Intraocular Pressure Measurements Using the Ocular Response Analyzer. J Glaucoma 2006;15:364–370.
3 - Liu J, Roberts CJ. Influence of corneal biomechanical properties on intraocular pressure measurement: quantitative analysis. J Cataract Refract Surg. 2005 Jan;31(1):146-55.
4 - Herbert E. Kaufman, MD. Pressure Measurement: Which Tonometer? Symposium on Glaucoma. Vol 11, number 2.
5 - Robert N. Weinreb, James D. Brandt, David Garway-Heath and Felipe Medeiros World Glaucoma Association on Intraocular Pressure; Consensus Series 4; May 5, 2007, Pg 18.
6 - Aashish Anand, MD, Carlos Gustavo De Moraes, MD, Christopher C Teng, MD, Celso Tello, MD, Jeffrey M Liebmann, MD Robert Ritch, MD. Lower Corneal Hysteresis Predicts Laterality in Asymmetric Open Angle Glaucoma, IOVS Papers in Press. Published on June 23, 2010 as Manuscript iovs.10-5580.
7 - Morita T, Shoji N, Kamiya K, Hagishima M, Fujimura F, Shimizu K. Intraocular pressure measured by dynamic contour tonometer and ocular response analyzer in normal tension glaucoma. Graefes Arch Clin Exp Ophthalmol DOI 10.1007/s00417-009-1169-4.

Reichert, Reichert Technologies, and Ocular Response Analyzer are registered trademarks of Reichert, Inc. AMETEK is a registered trademark of AMETEK, Inc. CPT is a registered trademark of the American Medical Association.