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(K_m), the maximum keratometry of anterior cornea(K_max), 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, K_m and K_max 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; P<0.01, P=0.011, 0.008, 0.014, 0.005), and also with the posterior corneal elevation(r=0.565, 0.369, 0.348, 0.306, 0.284; P<0.01, P=0.002, 0.003, 0.010, 0.017). Correlation between corneal densitometry and biomechanical properties: the corneal densitometry values of all ≤2mm, central >2 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.