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Editors Selection IGR 15-2

Anatomical Structures: Corneal Hysteresis as a Risk Factor for Progression

Comment by Tony Realini on:

84612 Relationship of Corneal Hysteresis and Anterior Lamina Cribrosa Displacement in Glaucoma, Wong BJ; Moghimi S; Zangwill LM et al., American Journal of Ophthalmology, 2020; 212: 134-143

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Wong and colleagues have conducted a prospective study to evaluate the relationship between corneal hysteresis (CH) and displacement of the anterior lamina cribrosa (ALC) over time in 147 eyes of 96 patients with glaucoma. CH was measured using the Reichert Ocular Response Analyzer at baseline, and ACL surface depth was measured using spectral domain optical coherence tomography a minimum of five times (mean 7.9) over a minimum of three (mean 3.5) years. A series of OCT images from 18 healthy subjects over the same time frame established the expected stability of ACL surface depth in the healthy state, while the mean rate of change in ACL surface depth among glaucomatous eyes was 0.78 µm/year in the posterior direction. In multivariable mixed-effects modeling, each 1 mm lower CH was associated with 0.66 µm/year of posterior ALC displacement. This is potentially a highly significant observation. More than a decade ago, several investigators (myself included) speculated that while CH's most obvious relationship to glaucoma was its effect on the accuracy of intraocular pressure (IOP) measurement, its characterization of anterior ocular biomechanical properties may reflect the nature of posterior ocular biomechanical properties. To wit, an eye with a less viscoelastic (not easily deformable) cornea may also have a less viscoelastic (less easily deformable) lamina, which in turn may be less well able to compensate for IOP-induced structural changes, thereby potentially increasing the risk of axonal injury and glaucoma progression. Several studies have established the relationship between CH and glaucoma progression risk. The study under discussion here may shed light on the mechanistic relationship between CH and progression risk.

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