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The biomechanical properties of the cornea are of great significance to corneal refractive surgery and postoperative corneal deformation, development, and pathology. In this paper, a geometric model of the cornea of myopia was established on the basis of the topographic data of a three-dimensional anterior segment analyzer, and the detection process of the visualized corneal biomechanics analyzer was simulated. Compared with the actual clinical detection results, the corneal elastic modulus and elastic modulus of 20 cases of myopia were calculated inversely. The mean value is 0.822 MPa±0.146 MPa. The calculated elastic modulus of myopia can provide a reference for the establishment of the finite element model of myopia, which is expected to provide a theoretical basis for the subsequent more accurate simulation of corneal refractive surgery and prediction of postoperative corneal mechanical properties.

Objective To obtain and analyze the effect of corneal collagen crosslinking (CXL) on corneal densitometry (CD) in patients with keratoconus (KC) by using the Pentacam 3D anterior segment analysis system. Methods Twenty-eight KC patients who visited the Chinese PLA General Hospital and underwent CXL from January 2017 to December 2019 were subjected and included in the KC-CD group. There were 14 patients who underwent monocular CXL, and the operated eyes were included in the CXL group and the non-operated eyes in the non-CXL group. CD values and data of corneal morphology, and the thinnest corneal thickness (TCT) were obtained and analyzed before and in 1 and 3 months, and 1 year after the CXL using the Pentacam 3D anterior segment analysis system. Nonparametric test, one-way Chi-square analysis, paired t-test and other statistical analyses were applied to compare CD before and after surgery in a cross-sectional and longitudinal manner. Results The CD values of 0~2 mm and 2~6 mm zones in the anterior, central, and posterior layers as well as in the total cornea were significantly higher (P < 0.05) in all KC patients undergoing CXL (KC-CD group) at 1 month after CXL when compared to the preoperative period. At 3 months after CXL, the CD values were higher in the 0~2 mm zones of the anterior layer, the central layer, and the total layer 0~2 mm than the values preoperatively (P < 0.01), whereas there was no statistical differences in the values in the 0~2 mm zone of the posterior layer. Only the CD values of the 0~2 mm zone in the anterior layer differed at 1 year after CXL when compared to the preoperative values (P=0.011). In the KC patients undergoing CXL in one eye, CD values in the non-CXL group did not change significantly before and after the CXL surgery, and the trend of CD values was the same in the CXL group as that in the KC-CD group. At 1 month postoperatively, a significantly higher CD value (P < 0.05) was observed in the CXL group compared to the non-CXL group in the 0~2 mm and >2~6 mm zones of the anterior layer, the central layer, the posterior layer, and the total layer. Compared with the Non-CXL group, the CD values of the above-mentioned layer of CXL group were still higher at 3 months after surgery (P < 0.05), but their mean CD values were decreased at 1 month after CXL. At 1 year after undergoing CXL, there were no significant changes in CD values in each layer between the CXL and non-CXL groups. Conclusion CXL causes an increase in CD value in KC patients with keratoconus, which peaks at 1 month postoperatively and then gradually decreased to normal level at 1 year after surgery.