Correlation of Corneal Hysteresis (CH) & Corneal Resistance Factor (CRF) with Geometric Corneal Para...
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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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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


Corneal Hysteresis (CH) & Corneal Resistance Factor (CRF) Factor (CRF) with Geometric Corneal Parameters

  • 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


Corneal spatial profile characteristics
Corneal Spatial Profile Characteristics Factor (CRF) with Geometric Corneal Parameters

  • 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


Our study
Our Study Factor (CRF) with Geometric Corneal Parameters

Objective:

  • to determine if Scheimpflug provided corneal spatial characteristics are better predictors of CH/CRF compared to CCT

ASCRS 2010


Methods
Methods Factor (CRF) with Geometric Corneal Parameters

  • 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


Demographics
Demographics Factor (CRF) with Geometric Corneal Parameters

  • 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


CCT vs. CRF/CH Factor (CRF) with Geometric Corneal Parameters

ASCRS 2010


Cornea thickness spatial characteristics
Cornea Thickness Spatial Characteristics Factor (CRF) with Geometric Corneal Parameters

  • 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


Modified slope
Modified Slope Factor (CRF) with Geometric Corneal Parametersα΄

  • 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


Linear regression analysis
Linear Regression Analysis Factor (CRF) with Geometric Corneal Parameters

ASCRS 2010


Stepwise logistic regression
Stepwise Logistic Regression Factor (CRF) with Geometric Corneal Parameters

  • 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


Conclusions
Conclusions Factor (CRF) with Geometric Corneal Parameters

  • 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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