Variability of Pentacam-derived Back Elevation Measurements in Keratoconus and Cross-linked Corneas

Completed

• Conditions: Keratoconus
• Interventions: Procedure: Corneal Collagen Cross-linking (CXL)

• Registration Number: NCT01471873
• Lead Sponsor: Democritus University of Thrace

Brief Summary

Primary objective of this study was to assess the intrasession, intersession and interobserver variability of the Pentacam-derived posterior corneal elevation measurements in keratoconus eyes and eyes that underwent Corneal Collagen Cross-liknking (CxL) treatment due to progressive keratoconus.

Detailed Description

The Pentacam Classic (Oculus Optikgerate GmbH, Heidelberg, Germany, software version 1.14r04) was used for the sake of the study.Two study groups were formed: 1) Keratoconus group (KC) included patients with progressive keratoconus and 2) Collagen-Cross-linking group (CXL) included keratoconus patients that had been treated with uneventful CXL at least on year prior to their enrollment in the study.

Three consecutive scans were obtained by two experienced operators. The same procedure was repeated within two weeks for the assessment of intersession variability. In all cases acceptable maps had at least 10.0mm of corneal coverage.All back elevation points were codified in order to facilitate statistical processing of data. Further to single point analysis, three additional parameters were evaluated: a) zone 4 parameter (z4) which derived by the analysis of all points at the central 4.0mm diameter zone, b) zone 8 parameter (z8) which derived by the analysis of all points at the central 8.0mm diameter zone, and, c) highest elevation point parameter (HEP), which derived by the analysis of the highest elevation points for all participants. Reproducibility of measurements was evaluated by means of intraclass correlation coefficients (ICC). Three different ICC types were calculated: a) intrasession ICC for both operators (ICC1 \& ICC2), b) interobserver ICC, and, c) intersession ICC. Moreover, Bland-Altman plots were used to evaluate the level of agreement between the two operators.

Study Timeline

• Study Start: 2011-03
• Primary Completion: 2011-09
• Study Completion: 2011-11
• Study First Submitted: 2011-11-09
• Study First Submitted QC: 2011-11-10
• Study First Posted: 2011-11-16
• Status Verified: 2017-01
• Last Update Submitted: 2017-01-14
• Last Update Posted: 2017-01-18

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 67

Inclusion Criteria

• Progressive keratoconus (Keratoconus group)
• Corneal collagen cross linking (CxL) treatment at least one year prior to enrollment (CxL group)

Exclusion Criteria

• Glaucoma
• Suspicion of glaucoma
• history of herpetic keratitis
• corneal scarring
• severe eye dryness
• pregnancy or nursing
• current corneal infection
• underlying autoimmune disease

Study & Design

• Study Type: OBSERVATIONAL
• Study Design: Not specified

Arm && Interventions

Group	Intervention	Description
Collagen-Cross-linking group (CXLG)	Corneal Collagen Cross-linking (CXL)	Collagen-Cross-linking group (CXLG) included keratoconus patients that had been treated with uneventful corneal collagen cross-linking (CXL) at least on year prior to their enrolment in the study.

Primary Outcome Measures

Name	Time	Method
Variability of posterior corneal surface elevation measurements within and between sessions and within and between observers.	2 weeks	The Pentacam Classic (Oculus Optikgerate GmbH, Heidelberg, Germany, software version 1.14r04) was used for the sake of the study. Three consecutive scans were obtained by two experienced operators for the assessment of intrasession and interobserver variability. The same procedure was repeated within two weeks for the assessment of intersession variability.Bland-Altman plots were used to evaluate agreement between the 2 operators. The reproducibility of all measurements was evaluated by means of the intraclass correlation coefficient(ICC).

Trial Locations

Locations (1)

Eye Institute of Thrace (EIT); 🇬🇷 Alexandroupolis, Thrace, Greece