Objective: To evaluate inter-corneal symmetry of biomechanical parameters in keratoconus patients as measured by an ultra-high frequency corneal visualization Scheimpflug technology (CorVis-ST).Methods: In this case series study, 40 bilateral keratoconus patients diagnosed with the Amsler-Krumeich keratoconus classification were recruited from December 2013 to July 2015 at the Optometry Outpatient of the Eye Hospital, Wenzhou Medical University. The same operator, using the same CorVis-ST instrument,measured each eye three times. Twelve inter-corneal parameters measured by the instrument were recorded,including 10 biomechanical parameters, intraocular pressure, and central corneal thickness. Student's t-test and Mann-Whitney U-test were used to compare inter-corneal differences, while inter-corneal agreement was evaluated by the Bland-Altman plot. Results: The 95% limits of agreement and agreement ratios of the12parameters were as follows: applanation 1 time (AP1 T), -0.56 - 0.61 ms (8.8%, Z =0.441,P =0.229); applanation 1 length, -0.75 - 0.77 mm (45.0%, t =-0.178, P =0.907); applanation 1 velocity,-0.063 - 0.053 m/s (37.0%, Z =-1.528, P =0.171); applanation 2 time (AP2 T), -1.01 - 0.84 ms (4.6%,t =-0.848, P =0.269); applanation 2 length, -0.96 - 1.02 mm (65.8%, t =-0.342, P =0.715); applanation 2 velocity, -0.22 - 0.22 m/s(50.0%, t=-0.087, P =0.812); maximum deformation time (T), -1.38 - 1.11 ms (8.5%,Z =-1.170, P =0.162); maximum deformation peak distance, -1.70 - 3.93 mm (78.8%, Z =-3.321, P =0.001);maximum deformation curvature, -2.30 - 2.74 mm (46.5%, t =1.014, P =0.287); maximum deformation amplitude, -0.34 - 0.28 mm (29.1%, t =-1.057, P =0.221); intraocular pressure, -3.61 - 3.91 mmHg (32.6%,t =-1.152, P =0.267); and central corneal thickness, -135.70 - 152.10 μm (32.3%, t =-0.698, P =0.323).Of all measured parameters, only AP1 T, AP2 T, and T had low agreement ratios, indicating high inter-corneal symmetry. Conclusions: In our study population of binocular keratoconus patients, the parameters
AP1 T, AP2 T, and T had high inter-corneal symmetry. Research protocols using the CorVis-ST to studykeratoconus should take these results into consideration during data analysis.