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Th. Filippopoulos, M.D. 1, 2 , K. Platari, M.D. 1 , An. Charonis, M.D., Ph.D. 1 ,

Correlation of Corneal Hysteresis (CH) & Corneal Resistance Factor (CRF) with Geometric Corneal Parameters. Th. Filippopoulos, M.D. 1, 2 , K. Platari, M.D. 1 , An. Charonis, M.D., Ph.D. 1 , M. Papathanassiou, M.D. 2 , G. Georgariou, M.D. 1 , I. Vergados, M.D., Ph.D 2 .

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Th. Filippopoulos, M.D. 1, 2 , K. Platari, M.D. 1 , An. Charonis, M.D., Ph.D. 1 ,

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  1. Correlation of Corneal Hysteresis (CH) & Corneal Resistance Factor (CRF) with Geometric Corneal Parameters Th. Filippopoulos, M.D.1, 2, K. Platari, M.D.1, An. Charonis, M.D., Ph.D.1, M. Papathanassiou, M.D.2, G. Georgariou, M.D.1, I. Vergados, M.D., Ph.D2. 1.Athens Vision Eye Institute 2. Attikon Hospital, Department of Ophthalmology, University of Athens Medical School The authors have no financial interest in the subject matter of this poster. ASCRS 2010

  2. Corneal Hysteresis (CH) & Corneal Resistance Factor (CRF) • CH demonstrates a good linear correlation to CCT • CH demonstrates less diurnal variability compared to IOP, CCT • CRF may be able to differentiate between normal and glaucomatous cohorts • in a multivariate analysis IOP appears to be more dependent on CRF compared to CCT 20ms Montañés JMet al. IOVS 2008; 49: 968-74 Kida T et al. IOVS 2006; 47: 4422-6 Medeiros FA et al. J Glaucoma. 2006; 15: 364-70 ASCRS 2010

  3. Corneal Spatial Profile Characteristics • proprietary (Pentacam) corneal spatial characteristics useful in keratoconus screening • Percentage Increase in Thickness (PIT) PIT: (CTx-TP)/TP % • Corneal Thickness Spatial Profile (CTSP) CTSP: (CTx)=f(x) Ambrosio R. et al. J Cataract Refract Surg 2006; 32: 1851-9 ASCRS 2010

  4. Our Study Objective: • to determine if Scheimpflug provided corneal spatial characteristics are better predictors of CH/CRF compared to CCT ASCRS 2010

  5. Methods • prospective random recruitment of one eye (n=117 eyes) from healthy refractive surgery candidates during 07/2009 • inclusion criteria: normal topography, normal corneal slit lamp examination • independent variables: age, gender, CCT, spherical equivalent, corneal curvature, corneal diameter, ACD, ACV, PIT, CTSP • linear regression analysis for individual variables • multivariate stepwise logistic regression ASCRS 2010

  6. Demographics • average age ± SD: 33.7 ± 9.8 years • gender: 60.7% female • average logMAR BCVA ±SD: 0.12 ± 0.1 • (Snellen equivalent ~ 20/25) • average SEq ± SD: -4.0 ± 2.7 D • average Ultrasonic CCT ± SD: 551 ± 29.2 μm • average Scheimpflug CCT± SD: 552 ± 27.4 μm • average CH ± SD: 10.6 ± 1.4 mmHg • average CRF ± SD: 10.7 ± 1.5 mmHg • average corneal diameter ± SD: 12.2 ± 0.4mm • average ACD ± SD: 3.3 ± 0.4 p=0.6, student’s t-test ASCRS 2010

  7. CCT vs. CRF/CH ASCRS 2010

  8. Cornea Thickness Spatial Characteristics • ΔCT= CTmax - TP • Percentage Increase in Thickness • (PIT)= (ΔCT/TP)% • CTSP can be expressed by the slope α (μm/mm) of a simplified linear function αx +β fitting our data • (α)= ΔCT/corneal radius average ± 1.96SD ASCRS 2010

  9. Modified Slope α΄ • effort to include CCT and CTSP (α) into one value • average cornea spatial characteristics of the cohort described by simplified linear function CTx=αavex +βave • α΄=((CTmax- βave)/cor. radius)/αave ASCRS 2010

  10. Linear Regression Analysis ASCRS 2010

  11. Stepwise Logistic Regression • dependent variable CH • final model included the following independent variables: • age (p=0.22) • corneal curvature (p=0.60) • spherical equivalent (p=0.03)* • CCT (p<0.000001)** • Percentage Increase in Thickness (PIT) (p=0.67) • ACD (p=0.83) ASCRS 2010

  12. Conclusions • CH and CRF are primarily dependent on CCT • CTSP/PIT parameters are not better predictors of corneal viscoelastic properties • in the multivariate model the spherical equivalent maintained statistical significance • further investigation of the relationship of CH/CRF to geometric characteristics including corneal volume may be warranted ASCRS 2010

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