Evaluation of Dynamic Corneal Response Parameters and the Biomechanical E-Staging After Accelerated Corneal Cross-Linking in Keratoconus

Abstract

Purpose: This study evaluated the biomechanical E-staging in progressive keratoconus (KC) corneas before and after epithelium-off accelerated corneal cross-linking (CXL, 9 mW/cm2, 10 min, 5.4 J/cm2). Design: German university-based retrospective longitudinal cohort study. Methods: The biomechanical E-staging for ectatic corneal diseases was applied retrospectively on 49 progressive KC corneas of 41 patients who underwent CXL. Main outcome parameters included the Corvis Biomechanical Factor (CBiF, the linearized Corvis Biomechanical Index), the biomechanical E-staging (E1 to E4 result of dividing the CBiF value range into 5 groups), maximal anterior keratometry (Kmax), anterior radius of curvature (ARC), and thinnest corneal thickness (TCT). They were evaluated at 2.1±2.0 months preoperatively (n=49 corneas, 41 patients) and postoperatively after 5.4±1.4, 11.3±1.8, and 23.4±1.6 months. Results: The CBiF decreased (5.1±0.5 | 5.0±0.5, P=0.0338) and the E-staging increased significantly (2.4±0.9 | 2.6±0.8, P=0.0035) from preoperatively to the first postoperative follow-up. The difference was not significant after 11 months and there were same values after 23 months. Kmax, ARC, and TCT slightly decreased (Kmax: 56.9±6.3, 54.3±5.1, 56.2±6.6, 54.0±5.2; ARC: 49.8±3.5, 48.9±3.2, 50.8±5.6, 49.0±3.7; TCT: 470±34, 454±36, 459±35, 466±39; preoperatively and 5, 11, and 23 months postoperatively). A postoperatively decreased TCT was associated with an increased E-stage, whereas an equal or increased TCT measurement after CXL was associated with equal or lower E-staging results. Conclusions: The biomechanical E-staging in KC corneas is influenced by TCT measurements and increases within the first postoperative months after CXL. On the long term, it indicates a postoperative KC stabilization, with comparable E-values to preoperatively at 11 and 23 months after CXL.

Das biomechanische E-Staging: In-vivo-Biomechanik beim Keratokonus

“…Daher wurde untersucht, wie sich das biomechanische E-Staging nach Crosslinking verhält (Epithelabrasio, „Accelerated Protocol“, 9 mW/cm 2 , 10 min, 5,4 J/cm 2 ). Hierfür wurden 49 Keratokonus-Hornhäute von 41 Patienten retrospektiv analysiert, bei denen mindestens eine präoperative sowie eine postoperative Corvis-ST-Messung nach etwa 1 Jahr vorlag 37 . Für einige dieser Augen lagen zusätzliche Messungen vor, sodass insgesamt 22 Keratokonus-Hornhäute (21 Patienten) 5 Monate nach Crosslinking, 49 Keratokonus-Hornhäute (41 Patienten) nach 11 Monaten und 21 Keratokonus-Hornhäute (18 Patienten) nach 23 Monaten ausgewertet wurden.…”

“…5 ), jedoch nicht innerhalb des 1. Jahres nach Durchführung eines Crosslinkings 37 , 38 . Dieses Ergebnis führte zu der Frage, warum das biomechanische E-Staging im 1.…”

“…For this reason, we investigated how the biomechanical E-staging behaves after cross-linking (epithelial debridement, “accelerated protocol”, 9 mW/cm 2 , 10 min, 5.4 J/cm 2) . For this purpose, we performed a retrospective analysis of 49 keratoconus corneas from 41 patients who had undergone at least one preoperative Corvis ST measurement and one postoperative measurement about a year after the procedure 37 . Additional measurements were available for some of these eyes, resulting in a total of 22 keratoconus corneas (21 patients) evaluated 5 months after cross-linking, 49 keratoconus corneas (41 patients) evaluated at 11 months, and 21 keratoconus corneas (18 patients) evaluated at 23 months.…”

“…This suggests that the biomechanical E-staging can be used in the long term to assess progression or stability after cross-linking ( Fig. 5 ), but not within the first year after the cross-linking procedure 37 , 38 . This result raised the question of why the biomechanical E-staging increases, on average, during the first year after cross-linking.…”

“…Daher wurde untersucht, wie sich das biomechanische E-Staging nach Crosslinking verhält (Epithelabrasio, "Accelerated Protocol", 9 mW/cm 2 , 10 min, 5,4 J/cm 2 ). Hierfür wurden 49 Keratokonus-Hornhäute von 41 Patienten retrospektiv analysiert, bei denen mindestens eine präoperative sowie eine postoperative Corvis-ST-Messung nach etwa 1 Jahr vorlag [37]. analysiert werden konnten.…”