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Jong-Mo Seo, Min-Won Seo, So Hyun Bae, Hee-Kyung Yang, Jeong-Min Hwang; Development of 3D mouse-assisted Hess-Lancaster test. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5213.
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© ARVO (1962-2015); The Authors (2016-present)
Traditional Hess-Lancaster test uses nine points for diagnosing which part of the ocular muscle is paralyzed, and it uses red/green glass lenses for the inhibition of binocular fusion mechanism. This method is simple and easy to follow, but the manual examination and charting of the result decreases the reproducibility. Computerized test has been developed, but using joystick, mouse and keyboard are not so much intuitive as using pointer. To enhance the user interface and the fidelity of the computer-based test, 3D mouse was adopted and the target was revised.
The software was developed on Windows 7 operating system with Application Programming Interface. And for the interactive and efficient test, 3D mouse (SpaceNavigator, 3Dconnection Inc.) was adopted. Nine reference points for the test are equally separated in distance, and the sequence of the test point is determined in pseudo-random manner, thus all points will be evaluated without duplication. Evaluation point will be displayed with empty circle with the color of red or green as a reference. And around this circle, the opposite color pair, green or red empty circle is displayed as a mobile target, so the patient should control 3D mouse in x- or y-direction to overlap the mobile circle onto the reference circle. This result reflects the deviation angle according to the gaze. On confirming the position of the second circle by clicking, reference circle will be changed to vertical bar, and the mobile circle will be changed to rotated bar, so the patient should rotate mobile bar until it is aligned to the reference bar by rotating 3D mouse. This result reflects the deviation of torsion on each gaze. By this way, all points were evaluated in terms of deviation angle and torsion.
18 points of pseudo-random sequence evaluation (9 points for each eye) prevented the patient to notice which eye is being tested or which point will be displayed next time. This reduces the patient’s cheating for secondary gain. By separating circle matching and bar matching, patient’s attention can be increased in each sequence test. And by using 3D mouse, all interactions were integrated into single interface which can be used easily by the examinee.
By using 3D mouse and the variable target, computerized Hess-Lancaster test was developed. This test might enhance the performance and the reliability of the computer-based clinical evaluation of the paralytic strabismus.
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