Researchers who previously reported that corneal hysteresis (CH) was associated with glaucoma progression1 have found that it should be considered a new risk factor for developing the disease.2 For every 1 mm Hg reduction in CH, the risk of developing glaucoma increased 21%.
Study specifics. CH, a measure of the cornea’s viscoelasticity, is the difference (measured in mm Hg) between the pressure at which the cornea bends inward during an air jet applanation and the pressure at which it bends out.
For this prospective observational cohort study, the researchers evaluated 199 glaucoma suspects (287 eyes) who had a history of intraocular pressure (IOP) > 21 mm Hg and/or suspicious appearance of the optic nerve, with normal visual fields (VFs) at baseline. CH measurements were acquired at baseline using the Ocular Response Analyzer (ORA; Reichert Technologies), and the patients were followed an average of 4 years.
Results. Glaucoma development, defined as 3 consecutive abnormal standard automated perimetry tests during follow-up, occurred in 19% of eyes.
The study found that lower baseline corneal hysteresis measurements were significantly associated with increased risk of developing glaucomatous VF defects over time, even after adjusting for age, IOP, corneal thickness, and pattern standard deviation.
At baseline, CH was lower in those who developed glaucoma than in those who did not develop glaucoma (CH of 9.5 mm Hg vs. 10.2 mm Hg).
Predictive power. The study also found that CH may be a stronger risk factor for glaucoma than central corneal thickness (CCT), said coauthor Felipe A. Medeiros, MD, PhD, at Duke University in Durham, North Carolina. He added that this finding probably is related to the fact that thickness is just 1 component related to corneal biomechanics.
But unlike CCT, which affects estimations of IOP, there appears to be only a weak relationship between CH and IOP. “Corneal hysteresis may actually act more like a surrogate marker for the biomechanical properties of tissues in the back of the eye,” Dr. Medeiros said.
What next? Now, along with IOP, age, and CCT, another risk factor has been added to the constellation of those associated with glaucoma. “The challenge,” said Dr. Medeiros, “is how to develop new objective risk calculators that merge all these factors.” In the meantime, he advised doctors to consider measuring CH in glaucoma suspects. Eyes with a low CH would probably need to be monitored more often or receive early treatment, he said.
1 Medeiros FA et al. Ophthalmology. 2013;120(8):1533-1540.
2 Susanna CN et al. Am J Ophthalmol. Published online Jan. 2, 2018.
Relevant financial disclosures—Dr. Medeiros: NIH: S; Reichert: C,S.
For full disclosures and the disclosure key, see below.
Full Financial Disclosures
Dr. Adrean Allergan: C,S; Genentech: C,S; Ohr Pharmaceuticals: C,S; Ophthotech: C,S; Regeneron: C,S; SciFluor Life Sciences: C,S.
Dr. Fieß None.
Dr. Medeiros Alcon: C; Allergan: C; Bausch + Lomb: S; Carl Zeiss: C,S; Heidelberg Engineering: C,S; Merck: S; NIH: S; Novartis: C; Sensimed: S; Topcon: S; Reichert: C,S.
Dr. Whalen None.
||Consultant fee, paid advisory boards, or fees for attending a meeting.
||Employed by a commercial company.
||Lecture fees or honoraria, travel fees or reimbursements when speaking at the invitation of a commercial company.
||Equity ownership/stock options in publicly or privately traded firms, excluding mutual funds.
||Patents and/or royalties for intellectual property.
||Grant support or other financial support to the investigator from all sources, including research support from government agencies (e.g., NIH), foundations, device manufacturers, and/or pharmaceutical companies.
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