Abstract: Objective To compare the subjective squint deviation(SSD) in patients with intermittent exotropia detected with synoptophore method and computer-based perceptual eye position (PEP) test. Design Prospective comparative case series. Participants 355 patients with intermittent exotropia. Methods The long-distance SSD was detected with synoptophore method and, at the same time, middle-distance SSD was detected with the computer-based PEP test. Main Outcome Measures Horizontal SSD and vertical SSD. Results With synoptophore method, the mean SSD in the horizontal direction was (-8.85±5.39) °, and mean vertical deviation of eye position was (2.13±1.33)°. With PEP test, the mean SSD in the horizontal direction was (287.41±220.80) (1°=53 pixels) pixels, and mean vertical deviation of eye position was (25.06±33.95) pixels. The detection rate of horizontal SSD was higher with PEP test (84.79%, 301/355) than with synoptophore method (63.10%, 224/355) (χ2=51.115, P=0.000). The detection rate of vertical eye position deviation was higher with PEP test (82.82%, 294/355) than with synoptophore method (6.44%, 23/355) (χ2 = 267.033, P=0.000). The horizontal SSD was (-10.48±3.19)° and the vertical SSD was (-2.13±1.33)° in 23 patients with vertical eye position deviation detected with synoptophore method, and there was no linear correlation between them (r=-0.211, P=0.335). The horizontal SSD was (291.05±220.43) pixels, and the vertical SSD was (25.06±33.95) pixels, and there was a linear correlation between them (r=0.406, P=0.000). In 206 patients simultaneously having horizontal SSD of two methods, the SSD was (-8.84±5.31)° in synoptophore method and (296.14±222.19) pixels in PEP test, respectively. And there was a linear correlation between them (r=-0.301, P=0.000). In 22 patients simultaneously having the vertical SSD of two methods, the SSD was (2.09±1.34)° in synoptophore method, and (42.95±40.88) pixels in PEP test. And there was no linear correlation between them (r=0.119, P=0.598). Conclusion In patients with intermittent exotropia, both SSD and PEP can reflect the horizontal eyes position deviation in the state of binocular differentiate gaze, but the detection rate of PEP test in the vertical direction was much higher than that of synoptophore method. The vertical PEP increased accordingly with the enlargement of the horizontal PEP. PEP test was a more sensitive and more comprehensive test of the eye position deviation. （Ophthalmol CHN，2020, 29： 133-137）

Key words: visual perception, binocular vision, intermittent exotropia