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

Democritus University of Thrace

Status: Completed

Conditions: Keratoconus

Treatments: Procedure: Corneal Collagen Cross-linking (CXL)

Study type: Observational

Funder types: Other

Identifiers

NCT01471873

25/27-09-2011

Details and patient eligibility

About

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.

Full 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.

Enrollment: 67 patients

Sex: All

Ages: 18+ years old

Volunteers: No Healthy Volunteers

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

Trial design

67 participants in 2 patient groups

Keratoconus Group (KG)

Description:

Keratoconus group (KG) included patients with progressive keratoconus.

Collagen-Cross-linking group (CXLG)

Description:

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.

Treatment:

Procedure: Corneal Collagen Cross-linking (CXL)