Manual compass measurement and trigonometric determination of proptosis.

PURPOSE: To determine the accuracy of manual compass measurement and trigonometric determination of proptosis (MCMATDP). METHODS: This agreement study included 120 eyes without eye diseases or injury of 60 patients who visited the ophthalmic clinic of Peking University Shenzhen Hospital from February 2020 to June 2020. The absolute values of proptosis were measured by MCMATDP and computed tomography (CT). The differences between the two methods were shown by Bland-Altman plot. RESULTS: The cohort comprised 25 males and 35 females (average age 38.3 years). The absolute value of proptosis measured by CT was correlated with the MCMATDP. Further analysis showed that a 95% limit of agreement (LoA) was - 0.53 to 0.60 mm in the right eye and - 0.46 to 0.55 mm in the left eye between CT and MCMATDP. In addition, the 95% LoA was - 0.49 to 0.60 mm in both eyes between the two methods. All points were < 5% in Bland-Altman plots. CONCLUSIONS: Compared to CT, MCMATDP is rather consistent in proptosis measurement. The new method is feasible in clinical practice when measuring proptosis. With the development of non-contact intelligent measurement software and the continuous improvement in measurement accuracy, a non-invasive, simple, and inexpensive measurement mode is true based on the theory of MCMATDP.