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Corneal Biomechanics as a Risk Modifier: Last-Month Evidence · Glaucoma, Vision & Longevity: Supplements & Science

• 0:00
  SPEAKER_00: Understanding corneal biomechanics and glaucoma risk.
• 0:03
  SPEAKER_00: Glaucoma is an eye disease where damage to the optic nerve leads to vision loss.
• 0:08
  SPEAKER_00: The main known risk factor has long been high intraocular pressure, IOP.
• 0:12
  SPEAKER_00: However, newer research shows the biomechanical properties of the cornea, essentially how springy or deformable the cornea is, also influence glaucoma risk.
• 0:22
  SPEAKER_00: Two key measures are corneal hysteresis, CH, and dynamic corneal response, DCR, parameters.
• 0:28
  SPEAKER_00: CH measures how well the cornea absorbs and dissipates energy.
• 0:32
  SPEAKER_00: Think of it as corneal shock absorption.
• 0:35
  SPEAKER_00: DCR parameters come from devices like the Corvus ST, which use a quick air puff and high-speed camera to record corneal deformation.
• 0:43
  SPEAKER_00: These measures are now easier to get in the clinic thanks to instruments such as the Ocular Response Analyzer, ORA, and Corvus ST.
• 0:52
  SPEAKER_00: Recent evidence suggests both CH and DCR can help predict glaucoma development and progression beyond IOP and corneal thickness, CCT.
• 1:00
  SPEAKER_00: Measuring corneal hysteresis and corneal response.
• 1:03
  SPEAKER_00: The ORA, introduced in 2005, uses an airpuff and infrared light to estimate CH.
• 1:09
  SPEAKER_00: It reports two values, CH and a related corneal resistance factor, CRF.
• 1:14
  SPEAKER_00: The newer Corvus ST system uses a high-speed Scheinflug camera, over 4,300 frames sec to visualize the actual corneal movement during an airpuff.
• 1:24
  SPEAKER_00: It yields many dynamic response metrics like deformation amplitude, inverse radius, stiffness beyond CH.
• 1:30
  SPEAKER_00: Importantly, each device produces different parameters and they are not interchangeable.
• 1:35
  SPEAKER_00: For example, one study found that the Corvus ST's biomechanically corrected IOP did not match the ORA's cornea-compensated IOP, IOPCC.
• 1:45
  SPEAKER_00: The two methods showed weak agreement and should not be used interchangeably.
• 1:50
  SPEAKER_00: In practical terms, CH from ORA and DCR metrics from Corvus reflect related but distinct corneal properties.
• 1:58
  SPEAKER_00: Clinicians are beginning to incorporate these tests.
• 2:00
  SPEAKER_00: One expert review even recommends checking corneal biomechanics at baseline in all glaucoma patients and suspects.
• 2:08
  SPEAKER_00: This means measuring CH and possibly corvus metrics as part of the initial exam.
• 2:13
  SPEAKER_00: In summary, corneal biomechanics can now be measured clinically, and experts suggest doing so in glaucoma care.
• 2:20
  SPEAKER_00: Biomechanics and glaucoma onset, evidence is growing that low CH predicts glaucoma development.
• 2:26
  SPEAKER_00: In one large prospective study of glaucoma suspects, ocular hypertension, about 19% developed glaucoma over four years.
• 2:34
  SPEAKER_00: Eyes that converted had significantly lower baseline CH.
• 2:38
  SPEAKER_00: Specifically, each 1 mm Hertzgrame lower CH at baseline raised the hazard of developing glaucoma by about 20%, multivariable hazard ratio 1.2, 95% CI 1.01 to 1.42.
• 2:51
  SPEAKER_00: In that study, after controlling for age and other factors, neither baseline IOP nor corneal thickness CST was a significant predictor, only CH was.
• 3:00
  SPEAKER_00: In practical terms, a 10mm Hergdram CH and an 8mm DRAM CH would translate to roughly 1.2 squared and 1.44, 44%.
• 3:08
  SPEAKER_00: Higher risk for the eye with 8 mmHgs.
• 3:11
  SPEAKER_00: This suggests CH adds independent prognostic value.
• 3:14
  SPEAKER_00: Someone with borderline pressures but very low CH may be at higher risk than predicted by IOP CCT alone.
• 3:21
  SPEAKER_00: The American Academy of Ophthalmology similarly notes that lower CH is associated with faster progression in glaucoma patients, including those with normal tension glaucoma, IOP in normal range.
• 3:33
  SPEAKER_00: Their review found that patients with normal tension glaucoma had lower CH than IOP matched normals, indicating CH matters even when IOP is low.
• 3:43
  SPEAKER_00: In other words, corneal biomechanics seem to affect the optic nerve's vulnerability to pressure.
• 3:48
  SPEAKER_00: In some, patients with higher CH tend to have slower or less glaucoma risk, whereas low CH consistently signals higher risk of onset and damage.
• 3:58
  SPEAKER_00: Biomechanics and glaucoma progression.
• 4:00
  SPEAKER_00: Corneal biomechanics also predict progression in established glaucoma.
• 4:04
  SPEAKER_00: In a landmark perspective study, each 1 mm Hertz lower CH predicted about zero, 25% faster loss per year of the Visual Field Index, VFI.
• 4:14
  SPEAKER_00: Over several years, this difference compounds meaningfully.
• 4:17
  SPEAKER_00: Importantly, CH explained a larger share of progression risk than CCT, about 17.4% of the variation in visual field change versus only 5.2% for CCT.
• 4:28
  SPEAKER_00: This shows CH adds predictive power beyond thickness and pressure.
• 4:32
  SPEAKER_00: Additionally, in that study, the effect of IOP on progression was stronger in eyes with low CH.
• 4:38
  SPEAKER_00: Eyes with both high IOP and low CH had especially fast damage rates.
• 4:43
  SPEAKER_00: In plain terms, imagine two glaucoma patients with the same pressures and corneal thickness.
• 4:48
  SPEAKER_00: If one has low CH, softer cornea, and the other has high CH, stiffer cornea, the low CH patient is likely to worsen faster.
• 4:56
  SPEAKER_00: Clinicians might see similar effects in visual field tests.
• 4:59
  SPEAKER_00: Lower CH often correlates with faster field loss, even after accounting for IOP.
• 5:05
  SPEAKER_00: For example, Medeiros et al.
• 5:07
  SPEAKER_00: reported that weaker CH was significantly associated with risk of faster progression, supporting the idea that the cornea's shock absorbing ability helps protect the optic nerve.
• 5:18
  SPEAKER_00: Incremental value over IOP and CCT.
• 5:21
  SPEAKER_00: Importantly, many studies show CH provides added value beyond known risk factors.
• 5:26
  SPEAKER_00: In both onset and progression analyses, CH remained significant even after adjusting for IOP and CCT.
• 5:32
  SPEAKER_00: In the glaucoma suspect study, neither IOP nor CCT predicted conversion once CH was in the model.
• 5:40
  SPEAKER_00: In the progression study, CH explained about three times more of the outcome variance than CCT.
• 5:46
  SPEAKER_00: In practice, this means CH can refine risk estimates.
• 5:49
  SPEAKER_00: For example, an ocular hypertensive patient with moderate pressure but very low CH would be reclassified as higher risk than one with the same pressure but higher CH.
• 5:59
  SPEAKER_00: Clinicians should thus consider CH in addition to IOP and thickness.
• 6:03
  SPEAKER_00: The combination gives a fuller picture.
• 6:05
  SPEAKER_00: As one recent review concluded, measuring CH complements current structural and functional assessments when gauging risk.
• 6:13
  SPEAKER_00: Subgroup findings.
• 6:15
  SPEAKER_00: Evidence suggests the influence of CH holds across different patient groups.
• 6:20
  SPEAKER_00: For instance, CH is lower in all major glaucoma types compared to normals, including primary open angle, angle closure, and pseudoexfoliation glaucoma.
• 6:29
  SPEAKER_00: This includes normal tension glaucoma.
• 6:31
  SPEAKER_00: Even when pressures are similar, NTGIs have lower CH than non-glaucoma eyes.
• 6:37
  SPEAKER_00: In Susanna's cohort, no subgroup, age, gender, race, overrode the CH effect.
• 6:43
  SPEAKER_00: African-American race did not significantly alter CH's predictive power in her study.
• 6:47
  SPEAKER_00: In Mendelian terms, CH appears a generalized risk marker.
• 6:51
  SPEAKER_00: Even patients on different treatments show this pattern.
• 6:54
  SPEAKER_00: One study found that treated and untreated glaucoma eyes both differed from normals in certain corneal stiffness metrics.
• 7:01
  SPEAKER_00: Taken together, current data imply low CH is a red flag in virtually any glaucoma suspect or patient, regardless of ethnicity or glaucoma subtype.
• 7:11
  SPEAKER_00: Device differences and measurement precision.
• 7:14
  SPEAKER_00: Different instruments can yield somewhat different biomechanical numbers.
• 7:17
  SPEAKER_00: The RA provides CH and CRF, while the Corvus ST generates many indices, deformation amplitudes, stiffness parameters, etc.
• 7:27
  SPEAKER_00: Because of this, parameters are not directly interchangeable between devices.
• 7:31
  SPEAKER_00: For example, one study found that Corvus's BIOP and OROPC could not be used interchangeably, their agreement was poor even in normal eyes.
• 7:40
  SPEAKER_00: In short, an aura-measured CH is not the same as any single Corvus parameter.
• 7:45
  SPEAKER_00: When applying research findings, physicians should match the metric to the device used in the study.
• 7:51
  SPEAKER_00: As for reliability, both devices have good test-retest performance in normal eyes.
• 7:56
  SPEAKER_00: A repeatability study of the Corvus ST found most deformation-related parameters had coefficients of variation below 4%.
• 8:04
  SPEAKER_00: That same work reported good precision, repeatability, and reproducibility for its measurements.
• 8:10
  SPEAKER_00: Similarly, the ORA has shown high reliability for CH.
• 8:14
  SPEAKER_00: One report found Kronbach's alpha for zero.
• 8:17
  SPEAKER_00: 9.
• 8:18
  SPEAKER_00: Indicating excellent repeatability of CH in normal subjects.
• 8:22
  SPEAKER_00: In practice, this means a patient's CH measurement is fairly consistent from one visit to the next under stable conditions.
• 8:30
  SPEAKER_00: Of course, factors like variances in IOP and measurement technique can still introduce some fluctuation, but overall both CH and Corvus metrics are reasonably reproducible.
• 8:40
  SPEAKER_00: Putting it all together, clinical risk algorithms.
• 8:43
  SPEAKER_00: Given these findings, clinicians can refine their risk assessment by incorporating corneal biomechanics into decision making.
• 8:50
  SPEAKER_00: For example, in a glaucoma suspect or ocular hypertensive, one could add an adjustment for CH when deciding how aggressively to treat or follow-up.
• 8:58
  SPEAKER_00: A simple approach, calculate baseline risk using IOP, CCT, Age, etc., then increase that risk estimate for low CH.
• 9:07
  SPEAKER_00: The Susanna study implies roughly a 20% higher hazard per memometer lower CH.
• 9:12
  SPEAKER_00: So if two patients have the same age, IOP and CCT, the one with a CH5 mm lower would have about 1.25 cores 2.5 times the risk of glaucoma.
• 9:23
  SPEAKER_00: Practically speaking, a patient on the fence for treatment might be treated early if CH is low but monitored if CH is high.
• 9:30
  SPEAKER_00: For progression in known glaucoma, a similar logic applies.
• 9:33
  SPEAKER_00: Even if IOP is controlled, a low CH, e.g.
• 9:36
  SPEAKER_00: in the lower 20% of values, signals faster loss.
• 9:39
  SPEAKER_00: In such cases, clinicians might opt for a lower pressure target or consider earlier surgery.
• 9:45
  SPEAKER_00: Conversely, a higher CH, stronger cornea, might mean the eye tolerates pressure better, allowing a more moderate approach.
• 9:52
  SPEAKER_00: Although formal guidelines for CH-based algorithms are not yet established, one can adapt existing risk models like those from OHTS or AGS by inserting CH as an independent factor.
• 10:03
  SPEAKER_00: In sum, if CH is low, especially well below average, prone to consider more aggressive management.
• 10:10
  SPEAKER_00: If CH is high, standard risk thresholds may suffice.
• 10:13
  SPEAKER_00: Visual field and imaging follow-up should also be more frequent for low CHIs.
• 10:18
  SPEAKER_00: In conclusion, the latest evidence mid-2026 reinforces that corneal biomechanics are useful modifiers of glaucoma risk.
• 10:26
  SPEAKER_00: They add predictive power on top of IOP and CCT.
• 10:30
  SPEAKER_00: The consensus is shifting toward using CH and DCR in practice.
• 10:34
  SPEAKER_00: Going forward, clinicians can integrate these factors into patient discussions and treatment plans, ultimately aiming to prevent vision loss by tailoring therapy to each eye's individual biomechanics.
• 10:46
  SPEAKER_00: Tags glaucoma risk factors, corneal hysteresis, corneal biomechanics, intraocular pressure, central corneal thickness, dynamic corneal response, ocular response analyzer, Corvus ST, glaucoma progression, risk assessment.
• 11:01
  SPEAKER_00: All links to sources are available in the text version of this article.
• 11:05
  SPEAKER_00: You can find the full article at VisualFieldtest.com.
• 11:08
  SPEAKER_00: Thanks for listening.
• 11:10
  SPEAKER_00: To check your visual field, click the link at the bottom of this article or visit visualfieldtest.com.