June 2019

GLAUCOMA

Presentation Spotlight
A glaucoma risk factor that physicians might not be measuring for yet


by Liz Hillman EyeWorld Senior Staff Writer


Dr. Radcliffe measures his own corneal hysteresis.
Source: Nathan Radcliffe, MD

 

There’s a test that can help assess a patient’s risk for glaucoma development and progression that Davinder Grover, MD, said many ophthalmologists are not using and may not even know about.
It’s called corneal hysteresis, which is a measure of how well the eye absorbs and dissipates energy. To Dr. Grover, corneal hysteresis is a “glaucoma vital sign” that he finds “essential” as he makes decisions for his patients’ glaucoma treatment plans.
Corneal hysteresis, as a biomechanical property of visco-elasticity, is measured by a device similar to the tonometer “puff test.” A bidirectional applanation system, the Ocular Response Analyzer (Reichert Technologies), calculates corneal hysteresis as the difference in pressure from when the cornea bends inward upon an air puff and the pressure when it bends outward again. A corneal hysteresis of 10 is average, above 10 is good, and below 10 is correlated with a greater risk for progression, Dr. Grover said.
Until somewhat recently there were not well-designed prospective studies confirming the connection between corneal hysteresis and progression or glaucoma development. In 2013, Medeiros et al. published a prospective longitudinal study that evaluated corneal hysteresis as a risk factor for glaucoma progression.1 Overall, corneal hysteresis measurements were found “significantly associated with glaucoma progression,” according to the investigators.
“Eyes with lower CH had faster rates of visual field loss than those with higher CH,” Medeiros et al. wrote. “The prospective longitudinal design of this study supports the role of CH as an important factor to be considered in the assessment of the risk of progression in patients with glaucoma.”
More specifically, corneal hysteresis was two times more predictive of visual field progression, compared to Goldman applanation, and three times more predictive than central corneal thickness.
Another study by Susanna et al. published in 2018 found that corneal hysteresis could be used as a risk factor for predicting even the development of glaucoma, with lower corneal hysteresis measurements significantly associated with increased risk.2
“The evidence for corneal hysteresis as a risk factor is in some ways stronger than the evidence for corneal thickness, which we all use and is the standard of care,” said Nathan Radcliffe, MD.
Recognition of corneal hysteresis as a risk factor, however, is lagging. Some say it’s just a research tool, Dr. Radcliffe said, but he countered that there are ways it directly impacts clinical management. It can help identify patients who are over or under treated; tells which eyes will have pressure reductions after cataract surgery; can help in MIGS decision making; and helps physicians understand how much pressure reduction they might get from starting a medication or from laser trabeculoplasty, Dr. Radcliffe said.
Dr. Grover thinks corneal hysteresis measurement is especially useful for low tension glaucoma or early glaucoma cases, finding that it helps him risk stratify. Dr. Radcliffe also said he measures hysteresis on almost all of his patients at some point within the first year.
“[Hysteresis] tells me how their eye is tolerating pressure,” he said. “Another way to think of it is how much biomechanical stress this eye is experiencing from pressure.”
The Ocular Response Analyzer also provides a measurement called corneal compensated IOP (IOPcc). This, Dr. Grover explained, takes into consideration the corneal hysteresis and other factors to give an output of what Reichert thinks the true IOP actually is. When corneal hysteresis is low, Dr. Grover observed, there is usually a discrepancy between IOPcc and the Goldman applanation measurement. At the 2019 Surgical Summit, Dr. Grover said the relationship between IOPcc and Goldman needs further investigation.
Dr. Radcliffe said corneal hysteresis serves as a model for technological adoption. In this case, he said, there is good data showing that this measurement is clinically helpful.
“But we don’t have a great economic story and in modern ophthalmic times, often procedures that have better reimbursement will grow faster, but the data is very clear that this test helps us better care for patients with glaucoma,” he said. “I think it’s only a matter of time before it is the standard of care.”

About the doctors

Davinder Grover, MD
Glaucoma Associates of Texas
Dallas

Nathan Radcliffe, MD
Assistant professor of ophthalmology
Icahn School of Medicine,
Mount Sinai
New York

References

1. Medeiros FA, et al. Corneal hysteresis as a risk factor for glaucoma progression: a prospective longitudinal study. Ophthalmology. 2013;120:1533–40.
2. Susanna CN, et al. A prospective longitudinal study to investigate corneal hysteresis as a risk factor for predicting development of glaucoma. Am J Ophthalmol. 2018;187:148–152.

Contact information

Grover
: dgrover@glaucomaassociates.com
Radcliffe: drradcliffe@gmail.com

A glaucoma risk factor that physicians might not be measuring for yet A glaucoma risk factor that physicians might not be measuring for yet
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