Conventional Versus Virtual Reality-Based Hess–Lancaster Assessment: Agreement and Repeatability in Ocular Motility Evaluation

Background: The conventional Hess–Lancaster test is widely used to assess ocular misalignment across diagnostic gaze positions, but it relies on subjective responses and manual recording. Virtual reality may provide a more standardized framework for ocular motility assessment. Objectives: To evaluate the agreement and within-method repeatability of point-by-point deviation measurements obtained with the conventional Hess–Lancaster test and a VR-based Hess–Lancaster assessment implemented in Dicopt Pro. Methods: This cross-sectional observational study included 52 adults with suspected or diagnosed ocular motility disorders. Participants underwent both assessments using the same predefined gaze positions. Agreement was assessed using Bland–Altman analysis, concordance correlation coefficients, mean absolute differences, and mixed-effects modeling. Repeatability was evaluated in a subset with repeated measurements using session-to-session differences and intraclass correlation coefficients. Results: The VR-based assessment showed moderate agreement with the conventional test, with a mean concordance correlation coefficient of 0.57 for both eyes. Mean bias was 1.22 prism diopters for the right eye and 0.10 prism diopters for the left eye. Repeatability estimates were moderate-to-good, with ICC values ranging from 0.62 to 0.83, although repeated measurements were available only in a subset of participants. Conclusions: The VR-based Hess–Lancaster assessment showed small mean differences and moderate agreement with the conventional test, although both methods should be interpreted within the context of the complete clinical examination.