Asymmetric whole eye movement during non-contact tonometry: independent validation and implications for corneal biomechanical parameters

Purpose The Corvis ST non-contact tonometer calculates whole eye movement (WEM) to isolate corneal deflection from globe displacement, assuming symmetrical retraction. This study aimed to validate the Corvis ST WEM parameter against an independent high-speed camera (HSC) system, quantify nasal-temporal asymmetry in globe retraction, and develop a correction method for identified asymmetries. Methods In this prospective cross-sectional study, 68 healthy subjects (mean age 22.65 ± 4.14 years) underwent Corvis ST measurement. In a subset of 20 participants, globe movement was simultaneously recorded using an orthogonal HSC system (3,030 fps). Raw displacement matrices were analysed to decompose the ocular response into translational and rotational components. Twelve WEM separation methods were compared using peripheral root-mean-square residuals. Results Robust regression achieved the lowest peripheral residuals (4.74 ± 2.97 µm), representing an 87.3% improvement over traditional edge-averaging (36.33 ± 18.76 µm, p < 0.001) and was optimal for 95.3% of measurements. HSC validation confirmed moderate-to-good reproducibility (ICC = 0.608 for amplitude and 0.720 for time). Significant nasal-temporal asymmetry was observed: nasal displacement exceeded temporal by 44–141 µm (N:T ratio 1.18–1.69, p < 0.001), with greater asymmetry in left eyes (N:T = 1.69 ± 0.34) than right eyes (N:T = 1.18 ± 0.20, p < 0.001). Globe retraction exhibited biphasic dynamics (slow phase 6.42 ± 3.17 ms, peak WEM at 21.07 ± 0.51 ms). Corneal curvature (SimK) predicted rotation amplitude in left eyes only (β=−0.47, p = 0.005). Deformation bounce was prevalent (63.0%), predominantly severe (55.9%) Conclusions The Corvis ST accurately measures overall globe displacement, but consistent nasal-temporal asymmetry introduces rotational error into standard WEM correction. An exploratory robust regression approach improved DCR parameter accuracy in this cohort, with potential implications for biomechanically corrected IOP, keratoconus screening indices, and clinical use of WEM as an orbital tissue biomarker. These correction findings require confirmation in larger, prospectively powered samples.