Clinical trial NCT01471873: Variability of Pentacam-derived Back Elevation Measurements in Keratoconus and Cross-linked Corneas
Official title: Variability of Pentacam-derived Back Elevation Measurements in Keratoconus and Cross-linked Corneas
Study type: OBSERVATIONAL
Overall status: COMPLETED
Conditions: Keratoconus
Keywords: Posterior corneal surface elevation
Pentacam-Scheimpflung imaging
variability
progressive keratoconus
corneal cross-linking
Lead sponsor: Democritus University of Thrace
Sponsor class: OTHER
First posted: 2011-11-16
Enrollment: 67
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Observational model: CASE_CONTROL
Time perspective: PROSPECTIVE
Sampling method: PROBABILITY_SAMPLE
Study population: Participants were recruited from the Cornea service of the EIT in a consecutive-if-eligible basis.

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.

Eligibility criteria: 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

Primary outcomes:
measure: Variability of posterior corneal surface elevation measurements within and between sessions and within and between observers.
timeFrame: 2 weeks
Secondary outcomes:
Other outcomes:
Locations:
city: Alexandroupolis
country: Greece
facility: Eye Institute of Thrace (EIT)
state: Thrace
Study officials:
References:
citation: Labiris G, Giarmoukakis A, Sideroudi H, Bougatsou P, Lazaridis I, Kozobolis VP. Variability in Scheimpflug image-derived posterior elevation measurements in keratoconus and collagen-crosslinked corneas. J Cataract Refract Surg. 2012 Sep;38(9):1616-25. doi: 10.1016/j.jcrs.2012.04.039.