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Updated: Oct 21, 2025
Recording Horizontal Saccade Performances Accurately in Neurological Patients Using Electro-oculogram
Published on: March 13, 2018
Audit and Comparison Between Radiographic Markers of Gaze Direction Using EOS Imaging - An Essential Step to
Hwee Weng Dennis Hey1, Joel Xue Yi Lim2, Chuen Seng Tan3
1Department of Orthopedic Surgery, National University of Singapore, Singapore.
Study Design:
Retrospective cohort study on prospectively implemented EOS protocol.
Objective:
This study aims to audit and compare existing radiological definitions of gaze direction-chin brow vertical angle (CBVA), McGregor slope (McGS), slope of line of sight (SLS), orbital-internal occipital protuberance (OIOP) slope angle, and Tangent to the hard palate (THP) in a neutral, healthy, and asymptomatic cohort.
Summary Of Background Data:
The ability to accurately define direction of gaze is the first step when striving for horizontal gaze restoration in any affected individual with rigid sagittal deformity. Yet, the radiological definition of gaze direction remains poorly standardized.
Methods:
Hundred healthy subjects who could achieve horizontal gaze underwent whole-body standing EOS radiographs taken under a strictly standardized protocol. Radiographic measurements of global spinal sagittal parameters and surrogate measures of horizontal gaze were analyzed and compared.
Results:
The mean age was 45 ± 15.9 years, with a balanced male-to-female-ratio. Their C7 SVA was -7.7 mm ± 24.8 mm, PI was 51.0o ± 11.4o, PI-LL was -0.9o ± 13.0o and T1-slope was 21.2o ± 9.2o. Measured horizontal gaze parameters were as follows: CBVA (1.07o ± 5.48o), McGS (-3.23o ± 5.63o), SLS (0.45o ± 5.34o), OIOP (5.03o ± 4.66o), THP (-0.17o ± 6.27o). CBVA correlated strongly with McGS (r = 0.679, P < 0.001), SLS (r = 0.592, P < 0.001), OIOP (r = 0.697, P < 0.001), and THP (r = -0.504, P < 0.001). OIOP had the lowest variance amongst all parameters and showed less variability compared to CBVA (SD 4.66 Var 21.69 vs. SD 5.48 Var 30.08, P = .012). Multivariate analysis showed that C2-7 angle was the only parameter found to be associated with OIOP values (P = 0.006).
Conclusion:
OIOP is the least variable, and most robust radiological method in determining gaze direction. It uses easily recognizable anatomical landmarks and an angular criterion, which makes it advantageous both with x-rays or slot scanners.Level of Evidence: 3.
