Analysis of the correlation between biomechanical properties and corneal densitometry in myopic eyes

Abstract

Abstract Background To investigate the correlation between corneal biomechanical characteristics (in vitro and in vivo) and corneal densitometry in myopia. Methods The Pentacam (Oculus, Wetzlar, Germany) corneal densitometry (CD) and Corvis ST (Oculus, Wetzlar, Germany) exams were conducted prior to surgery for myopic patients who were intended to undergo small-incision lenticule extraction (SMILE). CD values (grayscale units, GSUs), CCT (central corneal thickness) and in vivo biomechanical parameters were obtained. The stromal lenticule was subjected to a uniaxial tensile test to obtain the elastic modulus E in vitro. To exam correlations among biomechanical characteristics, CCT and CD values. Results In this study, 37 myopic patients (63 eyes) were included. The mean age of participants was 25.14 ± 6.74 years (range:16–39 years). The mean CD values of the total cornea, anterior layer, intermediate layer, posterior layer, 0–2 mm region and 2–6 mm region were 15.03 ± 1.23 GSU, 20.35 ± 1.98 GSU, 11.76 ± 1.01 GSU, 10.95 ± 0.83 GSU, 15.57 ± 1.12 GSU and 11.94 ± 1.77 GSU, respectively. Elastic modulus E (in vitro biomechanical indicator) was negatively correlated with intermediate layer CD (r=-0.35, P = 0.01) and 2–6 mm region CD (r=-0.39, P = 0.00). A negative correlation was also found between 0–2 mm central region CD and in vivo biomechanical indicator SP-HC (r=-0.29, P = 0.02). CCT was correlated with multiple biomechanical characteristics in vivo but didn’t interfere in vitro biomechanical indicator. Conclusions In myopic patients, densitometry is negatively correlated with biomechanical properties both in vivo and in vitro. With an increase in CD, the cornea deformed more easily. Elastic modulus can exclude the influence of CCT on corneal mechanics.