Which patients, as measured by Corvis (Corneal Visualization Scheimpflug Technology), are at higher risk of developing glaucoma?

Corvis ST Risk Stratification for Glaucoma Development

While Corvis ST (Corneal Visualization Scheimpflug Technology) measures corneal biomechanical properties including corneal hysteresis, the current evidence base and clinical guidelines do not provide specific Corvis ST parameters for glaucoma risk stratification—instead, clinicians should rely on corneal hysteresis measurements (typically obtained via Ocular Response Analyzer) combined with central corneal thickness to assess risk.

Understanding Corneal Biomechanics and Glaucoma Risk

The question addresses Corvis ST specifically, but the available guideline evidence focuses on corneal hysteresis as the key biomechanical parameter for glaucoma risk assessment:

Higher Risk Patients (Based on Corneal Biomechanics)

Patients with lower corneal hysteresis are at significantly increased risk for developing glaucoma:

• Each 1 mm Hg decrease in corneal hysteresis increases the risk of developing glaucoma by 21% in prospective studies 1
• Patients who developed glaucoma had baseline corneal hysteresis measurements of 9.5 ± 1.5 mm Hg compared to 10.2 ± 2.0 mm Hg in those who did not develop disease 1
• Low corneal hysteresis remains predictive even after adjusting for age, IOP, central corneal thickness, and treatment status 1
• Corneal hysteresis may be more strongly associated with glaucoma risk than central corneal thickness alone 2

Central Corneal Thickness Risk Stratification

The American Academy of Ophthalmology provides specific CCT thresholds for risk stratification that should be used in conjunction with biomechanical assessment:

• CCT ≤510 μm: Higher risk 3, 4
• CCT 511-580 μm: Intermediate risk 3, 4
• CCT >580 μm: Lower risk 3, 4

In the Ocular Hypertension Treatment Study, risk of developing POAG was greater in eyes with CCT <555 μm compared to those with CCT ≥588 μm 3

Additional Risk Factors to Integrate

When assessing glaucoma risk, corneal biomechanics must be considered alongside other established risk factors:

High-Risk Features Requiring Aggressive Monitoring

• Older age, particularly African Americans and Latinos over 40 years, and Caucasians over 65 years 3, 5
• Family history: 9.2-fold increased odds with first-degree relative with confirmed POAG 6; 5-fold increase with two or more affected siblings 3, 6
• Elevated IOP (though some patients develop glaucoma with normal IOP) 3, 5
• Low diastolic perfusion pressure <50 mmHg 3, 4
• Beta-zone parapapillary atrophy at baseline 3, 7
• Larger cup-to-disc ratio or smaller neuroretinal rim area 3

Clinical Application Algorithm

For patients undergoing corneal biomechanical assessment:

1. Measure corneal hysteresis (via Ocular Response Analyzer, as Corvis ST-specific guidelines are not yet established) 3

2. Measure central corneal thickness via ultrasonic pachymetry 3

3. Stratify risk based on combined parameters:

   • Highest risk: Low corneal hysteresis (<9.5 mm Hg) + thin CCT (≤510 μm) + additional risk factors 1, 4
   • Intermediate risk: Borderline hysteresis (9.5-10.2 mm Hg) + intermediate CCT (511-580 μm) 1, 4
   • Lower risk: Normal/high hysteresis (>10.2 mm Hg) + thick CCT (>580 μm) 1, 4

4. Use OHTS risk calculator to integrate age, vertical cup-to-disc ratio, pattern standard deviation, CCT, and IOP for 5-year risk assessment 4

5. Initiate monitoring protocol based on risk:

   • High-risk patients: Comprehensive ophthalmologic examination every 3-6 months with visual field testing, optic nerve imaging, and IOP measurement 7
   • Lower-risk patients: Annual comprehensive eye examinations 5

Critical Caveats

Do not use IOP correction nomograms based on corneal thickness or biomechanics—no validated correction formula exists 3, 4. Instead, diagnose glaucoma using clinical examination of the optic nerve head, RNFL and macular imaging, and visual field assessment 3

Corneal hysteresis is dynamic and may increase after IOP-lowering interventions, so serial measurements may be valuable for monitoring 2

In post-keratorefractive surgery eyes with thin CCT, IOP may be significantly underestimated by Goldmann applanation tonometry—consider alternative tonometry methods less influenced by corneal properties 3