LCD L38026: Corneal Hysteresis

This is a NON-coverage policy for all corneal hysteresis (CH) assessments as a means of risk assessment or monitoring for progression of ophthalmic disease activity.

Hysteresis is a measure of resistance to deformation to an applied force. CH is a measure of the viscoelastic dampening property of the cornea and is postulated to be a surrogate for the viscoelastic dampening properties of the posterior sclera and lamina cribrosa through which the retinal ganglion cell axons pass as they exit the eye. It has been theorized that glaucomatous damage to the retinal ganglion cell axons occurs at the lamina cribrosa and that viscoelastic differences in the lamina cribrosa are responsible for differential effects of intraocular pressure (IOP) within these tissues and contribute to the susceptibility to IOP-mediated damage. Studies show an association between a lower CH and glaucoma or glaucoma risk, and it has been proposed as a risk stratification tool for use in the treatment of glaucoma, glaucoma suspect, and ocular hypertension (OHT). CH is not itself a modifiable risk factor for glaucoma but theoretically could signal the need for more aggressive IOP reduction.

The Ocular Response Analyzer (ORA) (Reichert Inc., Buffalo, New York, USA) is a non-contact tonometer that measures CH. The ORA received U.S. Food and Drug Administration (FDA) 510(k) clearance in 2004 for the intended use of measurement of IOP and biomechanical response of the cornea “for the purpose of aiding in the diagnosis and monitoring of glaucoma.” 1 This device measures CH by measuring the difference of 2 applanation event pressures taken during the inward and outward movement of the cornea following delivery of a metered pulse of air.

A 2006 retrospective, observational study compared CH and central corneal thickness (CCT) on various indices of glaucomatous damage in 230 patients (mean 65 years), 85% diagnosed with primary open angle glaucoma (POAG) or glaucoma suspect, and 15% with angle-closure glaucoma, suspected angle-closure glaucoma, or secondary glaucoma. 2 Multivariate analysis found CCT, but not CH to be predictive of higher cup-to-disk ratio (CDR) (P=0.02 vs. P=0.36). Multivariate analysis found lower CH but not CCT to be predictive of visual field progression (P=0.30), but not after factoring in axial length (P=0.09). Neither CH nor CCT were significantly associated with worsening mean deviation (MD) or pattern standard deviation (PSD). A 2011 prospective observational study of 162 POAG subjects found no statistical difference in CH compared with 150 normal subjects. 3 A small (57 patients), 2012 retrospective study found both CH and IOP to be independent, statistically significant predictors of response to topical prostaglandin treatment. 4

A 2012 prospective cohort study of 153 patients (153 eyes) with established glaucoma evaluated the relationship between CCT and CH and their correlation with progressive visual field loss. 5 Baseline measurements included age, race, sex, CH, MD, PSD, CCT, and IOP (calculated by averaging the first 4 measurements following the baseline visual field (VF)), peak IOP, and corneal compensated IOP (IOPcc). Progression of glaucoma was determined by an automated pointwise linear regression analysis of visual field tests. Progression occurred in 25 enrolled eyes (16%) and demonstrated significantly lower CCT and CH compared with non-progressed eyes (p=0.04 and p A 2013 retrospective study of 131 glaucoma patients investigated the correlation between CH and other structural markers of glaucomatous damage on spectral domain optical coherence tomography (SDOCT). 6 In a multivariable analysis including MD, age, average retinal nerve fiber layer (RNFL) thickness, and glaucoma status, only MD (p=0.001) and age (p A 2017 cross sectional study compared single CH measurements among 123 patients (123 eyes) previously diagnosed with either glaucoma (high tension glaucoma, N=37; pseudoexfoliative glaucoma, N=12; normal tension glaucoma, N=24), OHT (N=28), or glaucoma-like optic discs (GLD) (N=22). 7 A one-way Analysis of Covariance (ANCOVA), correcting for differences in age and IOP, found mean CH to be significantly lower in patients with glaucoma versus those with OHT and GLD (p The following 4 studies by the same principal investigator included subjects who were part of the larger Diagnostic Innovations in Glaucoma Study (DIGS). 8-11 DIGS is a single-center, prospective, longitudinal cohort study of the relationships between optic nerve structure and glaucomatous vision loss, and the assessment of new diagnostic and monitoring modalities that could be used to mitigate functional vision loss by identifying at-risk patients through earlier detection and intervention.