Ignite Creation Date:
2024-05-05 @ 11:53 PM
Last Modification Date:
2024-10-26 @ 10:41 AM
Study NCT ID:
NCT01448408
Status:
COMPLETED
Last Update Posted:
2011-10-07
First Post:
2011-10-05
Brief Title:
Corneal Biomechanical Properties and Anterior Segment Parameters in Forme Fruste Keratoconus
Sponsor:
Democritus University of Thrace
Organization:
Democritus University of Thrace
Study Overview
Official Title:
Evaluation of the Sensitivity Specificity and Test Accuracy of Corneal Biomechanical Metrics Anterior Segment Data and a Combination Model in Differentiating Forme Fruste Keratoconus FFK From Healthy Corneas
Status:
COMPLETED
Status Verified Date:
2011-10
Last Known Status:
None
Delayed Posting:
No
If Stopped, Why?:
Not Stopped
Has Expanded Access:
False
If Expanded Access, NCT#:
N/A
Has Expanded Access, NCT# Status:
N/A
Acronym:
None
Brief Summary:
The present study attempts to evaluate the diagnostic capacity of a anterior segment parameters b biomechanical metrics and c a combination model in differentiating Forme Fruste Keratoconus FFK from healthy corneas
The study adhered to the tenets of the Declaration of Helsinki and written informed consent was given by all participants The study was conducted at the Eye Institute of Thrace ΕΙΤ in Alexandroupolis Greece EΙΤ is a Democritus University research institute focusing primarily on the conditions of the anterior segment of the eye
All participants underwent a complete clinical evaluation including review of medical history visual acuity measurements uncorrected and best corrected visual acuity placido disc topography Scheimpflug camera measurements ORA measurements slitlamp biomicroscopy and fundoscopic examination
All study participants were divided in two groups The FFK group FFKG consisted of patients with unilateral KC
The control group CG was formed by refractive surgery candidates who visited EITs outpatients service for their preoperative examination
CRF and CH parameters were obtained while the patient was sitting on a chair in front of the Ocular Response Analyzer ORA Reichert Ophthalmic Instruments Buffalo NY USA device Upon successful fixation of the patients eye on a red blinking target the operator activated the device An air puff was released by a non-contact probe which scanned the central area of the eye and sent a signal to the ORA In brief the air puff causes the cornea to move inward past applanation and into slight concavity After milliseconds the air pumps shut off the pressure decreases and the cornea begins to return in its normal state The system monitors the entire process and measures two pressure values which are determined from the inward and outward applanation processes The aforementioned measuring procedure enables the determination of CH which is related to the viscoelastic structure of the corneal tissue and is calculated as the difference between the two pressure values at the two applanation processes and CRF which is indicative of the overall resistance of the cornea and is calculated as a linear function of the two pressures associated with the two applanation In order to ensure accurate results ORA was done four times for each eye by the same operator Signals that differ significantly in appearance from the other signals from the same eye were deleted
Corneal Astigmatism Cyl Anterior Chamber Depth ACD Corneal Volume at 3mm CV3 at 5mm CV5 and overall CV Central Corneal Thickness CCT Thinnest Corneal Thickness TCT and TCT co-ordinates TCTx TCTy were obtained using Pentacam KISA index was calculated using Pentacam derived topography Pentacam is based on a rotating Scheimpflug camera and monochromatic slit light source a blue light emitted diode at 475 nm which rotate together After proper alignment of the patients head a fixation target is shown which guides the patients gaze A real time image of the patients eye is shown to the examiner on the computer screen and the image is manually focused and centered Acceptable maps had at least 100mm of corneal coverage Moreover images with extrapolated data in the central 90mm zone were excluded Regarding the measuring procedure itself patients were asked to blink and then look at the fixation device In case of low-quality image the procedure was repeated until the acceptable criteria were met
The data from the FFKG were compared with those from the CG in separate series analyses Receiver operating characteristics ROC curves were applied to determine the overall predictive accuracy of the test for each studied parameter as described by the area under the curve We also used this approach to identify the cut-off points for studied parameters to maximize sensitivity and specificity in discriminating FFK cases from normal corneas Logistic regression was used to support the cut-off point identified in the ROC curve analysis We determined a cutoff value that will gave us the best predictive fit for our sample data Furthermore logistic regression analysis was performed to determine the predictive capability of a model that combined both corneal biomechanical properties and pentacam derived anterior segment parameters
Differences between groups were evaluated using the Welch modified Students two sample t-test and Mann-Whitney U test according to normality of distribution for each parameter A Kolmogorov-Smirnov test of normality was applied to all variables of each group The level of significance for each parameter was set at p005 The Pearson and Spearman tests were performed in order to assess correlations between anterior segment parameters and biomechanical properties depending on their parametric evaluation
The study adhered to the tenets of the Declaration of Helsinki and written informed consent was given by all participants The study was conducted at the Eye Institute of Thrace ΕΙΤ in Alexandroupolis Greece EΙΤ is a Democritus University research institute focusing primarily on the conditions of the anterior segment of the eye
All participants underwent a complete clinical evaluation including review of medical history visual acuity measurements uncorrected and best corrected visual acuity placido disc topography Scheimpflug camera measurements ORA measurements slitlamp biomicroscopy and fundoscopic examination
All study participants were divided in two groups The FFK group FFKG consisted of patients with unilateral KC
The control group CG was formed by refractive surgery candidates who visited EITs outpatients service for their preoperative examination
CRF and CH parameters were obtained while the patient was sitting on a chair in front of the Ocular Response Analyzer ORA Reichert Ophthalmic Instruments Buffalo NY USA device Upon successful fixation of the patients eye on a red blinking target the operator activated the device An air puff was released by a non-contact probe which scanned the central area of the eye and sent a signal to the ORA In brief the air puff causes the cornea to move inward past applanation and into slight concavity After milliseconds the air pumps shut off the pressure decreases and the cornea begins to return in its normal state The system monitors the entire process and measures two pressure values which are determined from the inward and outward applanation processes The aforementioned measuring procedure enables the determination of CH which is related to the viscoelastic structure of the corneal tissue and is calculated as the difference between the two pressure values at the two applanation processes and CRF which is indicative of the overall resistance of the cornea and is calculated as a linear function of the two pressures associated with the two applanation In order to ensure accurate results ORA was done four times for each eye by the same operator Signals that differ significantly in appearance from the other signals from the same eye were deleted
Corneal Astigmatism Cyl Anterior Chamber Depth ACD Corneal Volume at 3mm CV3 at 5mm CV5 and overall CV Central Corneal Thickness CCT Thinnest Corneal Thickness TCT and TCT co-ordinates TCTx TCTy were obtained using Pentacam KISA index was calculated using Pentacam derived topography Pentacam is based on a rotating Scheimpflug camera and monochromatic slit light source a blue light emitted diode at 475 nm which rotate together After proper alignment of the patients head a fixation target is shown which guides the patients gaze A real time image of the patients eye is shown to the examiner on the computer screen and the image is manually focused and centered Acceptable maps had at least 100mm of corneal coverage Moreover images with extrapolated data in the central 90mm zone were excluded Regarding the measuring procedure itself patients were asked to blink and then look at the fixation device In case of low-quality image the procedure was repeated until the acceptable criteria were met
The data from the FFKG were compared with those from the CG in separate series analyses Receiver operating characteristics ROC curves were applied to determine the overall predictive accuracy of the test for each studied parameter as described by the area under the curve We also used this approach to identify the cut-off points for studied parameters to maximize sensitivity and specificity in discriminating FFK cases from normal corneas Logistic regression was used to support the cut-off point identified in the ROC curve analysis We determined a cutoff value that will gave us the best predictive fit for our sample data Furthermore logistic regression analysis was performed to determine the predictive capability of a model that combined both corneal biomechanical properties and pentacam derived anterior segment parameters
Differences between groups were evaluated using the Welch modified Students two sample t-test and Mann-Whitney U test according to normality of distribution for each parameter A Kolmogorov-Smirnov test of normality was applied to all variables of each group The level of significance for each parameter was set at p005 The Pearson and Spearman tests were performed in order to assess correlations between anterior segment parameters and biomechanical properties depending on their parametric evaluation
Detailed Description:
None
Study Oversight
Has Oversight DMC:
None
Is a FDA Regulated Drug?:
None
Is a FDA Regulated Device?:
None
Is an Unapproved Device?:
None
Is a PPSD?:
None
Is a US Export?:
None
Is an FDA AA801 Violation?:
None