2022 年 60 巻 1 号 p. 16-24
Cyclotropia is a condition in which one eyes is rotated about the anteroposterior axis. Cyclotropia affects the visual function;but, it is difficult to detect any external changes because of the rotational symmetry of the eyeballs in relation to the anteroposterior axis. Moreover, it takes time to receive an adequate medical diagnosis. To measure the degree of cyclotropia, a major amblyoscope that can display separate optotypes to the left and right eyes is widely used. However, a major amblyoscope is a highly specialized inspection equipment and is not suitable for daily measurements. In this study, we propose a method to quantify cyclodeviation by monocular vision using common devices such as smartphones and tablets that can be used for the routine testing of cyclotropia. In the proposed method, a tilted bar as an optotype is presented on the device to a monocularly blinded patient, and the patient is requested to make the tilted bar horizontal by rotating the device. The deviation between the optotype and the horizontal is measured when the horizontal is maintained based on the patient’s sense of equilibrium, and the cyclodeviation is measured as the sum of the deviations of both eyes. We implemented the proposed method as an application running on smartphones and tested the application on 47 patients with paralytic strabismus and 10 normal subjects. In patients with acquired paralytic strabismus, the correlation between the results of the proposed method and those measured with a major amblyoscope was 0.66, implying that the measurement results were good. The ROC analysis based on the results of all subjects for the classification of paralytic strabismus patients and normal subjects resulted in an AUC of 0.89, indicating that the implementation of the proposed method had a moderate predictive ability for cyclodeviation.