Comparison of corneal biomechanical parameters in healthy corneas with symmetric and asymmetric bow-tie topographic pattern with inferior and superior steepening.

ABSTRACT

PURPOSE: To compare the corneal biomechanical parameters in healthy corneas with symmetric and asymmetric bow-tie topographic patterns. METHODS: In this cross-sectional study, 144 eyes were divided based on inferior-superior asymmetry value (I-S) into symmetric (zero I-S - 0.50 to + 0.50 D) and asymmetric bow-tie topographic patterns with inferior (positive I-S + 0.51 to + 1.4 D) or superior (negative I-S - 2.5 to - 0.51 D) steepening. The biomechanical assessment was performed using Corvis ST and ocular response analyzer (ORA). A general linear model univariate analysis was used to compare the parameters, while the central corneal thickness, intraocular pressure, and age were considered covariates. RESULTS: Only the peak distance (PD) at the highest concavity phase (P = 0.007) and tomographic biomechanical index (TBI, P = 0.001) showed statistically significant differences between the three groups. For TBI, this difference was statistically significant between the positive I-S group separately with the zero I-S group (P < 0.001), and with the negative I-S group (P = 0.022). For PD, the significant difference was between the negative I-S group separately with zero I-S (P = 0.019), and positive I-S groups (P = 0.018). There was a statistically significant correlation between the I-S value with PD (r = 0.281, P = 0.001) and TBI (r = 0.170, P = 0.044). CONCLUSIONS: Most corneal biomechanical parameters are not statistically significant compared to the zero I-S group. However, superior steepening is associated with a stiffer response based solely on the shorter PD values seen in this group, and the group with the inferior steepening shows the highest or more suspicious values based on TBI.