Correlation among corneal densitometry, corneal topographic, and biomechanical properties in keratoconus

Abstract

AIM:To investigate the correlation among corneal densitometry, corneal topographic parameters, and corneal biomechanical properties in keratoconus.METHODS: Retrospective case study. A total of 70 eyes of 48 keratoconus patients were enrolled in this study. Corneal topography were measured using Pentacam, inclding the flat keratometry of anterior cornea(K1), the steep keratometry of anterior cornea(K2), the mean keratometry of anterior cornea(Km), the maximum keratometry of anterior cornea(Kmax), anterior corneal elevation(ACE), posterior corneal elevation(PCE), thinnest corneal thickness(TCT), and the distance from cone to apex(DCA). Corneal optical density of different corneal layers and zones were measured with the Scheimpflug-based Pentacam corneal densitometry module. Corneal biomechanical properties were measured using CorVis ST, inclding time of the first applanation(AT1), length of the first applanation(AL1), velocity of the first applanation(V1), time of the second applanation(AT2), length of the second applanation(AL2), velocity of the second applanation(V2), the highest concavity time(HCT), the highest concavity deformation amplitude(HCDA), the highest concavity radius(HCR), the highest concavity peak distance(HCPD), stiffness parameter applanation 1(SPA1), Ambrósio's relational thickness horizontal(ARTh).RESULTS: Correlation between corneal densitometry and topographic parameters: The corneal densitometry values of the anterior ≤2mm layer correlated with the K1, K2, Km and Kmax values positively(r=0.291, 0.315, 0.315, 0.387; P=0.015, 0.008, 0.008, 0.001). The corneal densitometry values of the anterior ≤2mm, anterior >2 and ≤6mm, total ≤2mm, total >2 and ≤6mm, and posterior >2 and ≤6mm layers correlated with the anterior corneal elevation positively(r=0.465, 0.302, 0.317, 0.291, 0.335; P2 and≤6mm, posterior >2 and ≤6mm, and total >2 and ≤6mm layers all correlated with AL1 negatively(r= -0.284, -0.290, -0.245, -0.326, -0.282, -0.395, -0.310; P=0.017, 0.015, 0.041, 0.006, 0.018, 0.001, 0.009). The corneal densitometry values of central ≤2mm, central >2 and ≤6mm, and posterior >2 and ≤6mm layers all correlated with AL2 negatively(r= -0.246, -0.256, -0.256; P =0.041, 0.032, 0.032). The corneal densitometry values of anterior ≤2mm layer correlated with HCR negatively(r= -0.308, P=0.010). The corneal densitometry values of central ≤2mm, posterior ≤2mm, and certral >2 and ≤6mm layers all correlated with HCT negatively(r= -0.292, -0.340, -0.262; P=0.014, 0.004, 0.028). The corneal densitometry values of anterior ≤2mm, total ≤2mm, and posterior >2 and ≤6mm layers all correlated with ARTh negatively(r= -0.430, -0.293, -0.319; P<0.01, P = 0.014, 0.007).CONCLUSION: The corneal densitometry values correlated with the severity of keratoconus and the biomechanical properties, and may became a potential diagnostic index of keratoconus.

Keywords

• keratoconus
• densitometry
• corneal topography
• biomechanics