Repeatability and Reliability of Corneal Tomography in Keratoconus Patients with Corneal Allogenic Intrastromal Ring Segments
Ugur Tunc1, Dilan Colak2, Burcu Yakut3, Fatma FeyzaNur Keskin Perk4, Metin Suleymanzade5, Sepideh Lotfi5, Aylin Kılıç51Department of Ophthalmology, Istanbul Medipol University, Faculty of Medicine, Istanbul, Türkiye2Department of Ophthalmology, Beyoglu Eye Training ad Research Hospital, Istanbul, Türkiye
3Department of Ophthalmology, Haseki Training and Research Hospital, Istanbul, Türkiye
4Department of Ophthalmology; Cam and Sakura City Hospital, Istanbul, Türkiye
5Department of Ophthalmology, Istanbul Biruni University, Istanbul, Türkiye
OBJECTIVES: To assess the repeatability and reliability of anterior and posterior corneal measurements in keratoconus patients who underwent corneal allogenic intrastromal ring segment (CAIRS) implantation using a Scheimpflug-based tomography system.
METHODS: This prospective observational study included 42 eyes: 20 keratoconic eyes that had undergone CAIRS implantation and 22 healthy controls. All participants were imaged with the Pentacam HR (Oculus Optikgeräte GmbH, Germany). Each eye underwent three consecutive scans during a single session. Repeatability was evaluated using within-subject standard deviation (Sw), repeatability index (RI), and tolerance index (TI), and reliability was assessed using intraclass correlation coefficients (ICC). A TI>0.36 was considered indicative of reduced repeatability.
RESULTS: Anterior corneal curvature parameters (K1 and K2) and pachymetric indices demonstrated excellent reliability (ICC>0.90) and acceptable repeatability (TI<0.36). In contrast, CAIRS-implanted eyes exhibited greater variability in Kmax, Kmean, anterior elevation, and several posterior corneal metrics, with TI values exceeding 0.36. Despite having high ICC values, posterior elevation showed the greatest variability. Pachymetry at the corneal vertex and the thinnest corneal thickness remained highly reproducible (TI 0.08 and 0.18, respectively), suggesting strong measurement accuracy.
DISCUSSION AND CONCLUSION: The implantation of CAIRS alters the shape of the cornea and decreases the repeatability of several tomography-derived metrics, especially posterior corneal indices and Kmax. Although overall reliability remains high, clinicians should cautiously interpret small postoperative changes in monitoring these parameters. Pachymetric measurements maintain excellent precision and can be reliably used for postoperative follow-up and progression assessment after CAIRS surgery.
Keywords: Cornea ectasia, intrastromal ring implantation, cornea tomography
Manuscript Language: English
