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Corneal hysteresis may help assess glaucoma risk
Lower baseline corneal hysteresis measurements were significantly associated with increased chances of developing glaucoma in a study.
Because the disease remains asymptomatic for a long time, corneal hysteresis (CH) could help in identifying patients who are at a higher risk of developing visual field defects so they can be monitored more closely and treated promptly, according to Susanna and colleagues.
Other studies, the authors noted, have measured CH in patients with progressing glaucoma, but this was the first time CH was evaluated as a predictive factor in a cohort of glaucoma suspects with normal visual field.
A total of 287 eyes of 199 patients were followed every 6 months for an average of 4 years. Fifty-four (19%) developed visual field defects at some point during the follow-up. In these patients, CH measurements, acquired at baseline with the Ocular Response Analyzer (Reichert Technologies) were significantly lower. Other parameters, such as IOP and central corneal thickness did not reach significance.
“Our findings suggest that evaluation of CH may add significant value to the assessment of risk of disease development in glaucoma suspects followed over time,” the authors wrote.
In a multivariable model, each 1 mm Hg lower CH was associated with a 21% increase in the risk of developing glaucoma.
The underlying cause of the correlation between CH and the risk of glaucoma are still unclear, according to the authors. CH does not seem to affect IOP and it is, therefore, more likely that other mechanisms are involved, such as a reduced resilience of the posterior ocular structures to IOP peaks or fluctuations.
“Future studies should attempt to incorporate CH measurements along with other known risk factors into models designed to improve risk assessment in glaucoma,” the authors concluded.
– by Michela Cimberle
Disclosure: Susanna reported no relevant financial disclosures. Please see the study for the other authors’ financial disclosures.
Perspective
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Building a risk profile is a critical component in the management of patients being monitored for the onset of manifest glaucoma. In the absence of frank functional loss, the decision to initiate treatment isn’t easy, and the clinician must weigh the consequences of medications or surgery against those of permanent visual field loss.
The Ocular Hypertension Treatment Study revealed five factors that predict the development of open-angle glaucoma: older age, higher IOP, large cup-to-disc ratio, greater pattern standard deviation and thinner central corneal thickness. Additional risk factors include African or Hispanic ethnicity, a family history of glaucoma, previous anterior segment trauma, use of topical steroids, high myopia, diabetes, extremes of systemic blood pressure (particularly hypotension) and, perhaps more controversially, obstructive sleep apnea and low cerebrospinal fluid pressure.
Susanna and colleagues suggest that low corneal hysteresis (possibly reflecting an inability of the corneoscleral shell to dampen IOP fluctuations and protect retinal ganglion cell axons) should be added to that list. Low corneal hysteresis is already acknowledged as a risk factor for both structural and functional progression; it follows that in a “glaucoma suspect” hysteresis in the single digits may be what tips the scale in favor of initiating treatment.