Exotropia is a kind of strabismus between exotropia and constant exotropia. The visual axes are often separated, and when looking at distance, the fused scattering amplitude exceeds the fused pooling amplitude, which produces exotropia; while when looking at near vision, it can maintain an orthotropic position, and exotropia occurs mostly preceded by exotropia. So what are the clinical diagnostic tools? 1.Cover test The patient is asked to look at a 30 cm target in front of him/her, such as a small light bulb, and the examiner covers one eye with the palm of his/her hand or a cardboard, when the cover is taken, both eyes are shifted, it means there is monocular strabismus. If both eyes are not shifted when the mask is taken, it means there is no strabismus; or if there is already strabismus, it is alternate strabismus. 2.Light method is the simplest and most commonly used method to measure strabismus. The examiner sits opposite to the patient and asks the patient to look at the light 30 cm in front of his eyes and observe the position of the light spot on the cornea of both eyes. If the light spot on the cornea is located at the pupillary margin, the strabismus is 10°-15°, 25°-30° for those located in the middle of the pupillary and corneal margins, and 45° for those located at the corneal margin. 3, prism masking method in front of the strabismus put a trigeminal prism (internal strabismus base outward, external strabismus base inward, upward strabismus base downward), gradually increase the trigeminal prism degree, alternately cover the two eyes, until the two eyes do not have eye position movement, the resulting trigeminal prism base, that is, the eye strabismus degree. 4, the visual machine to measure the oblique perspective in front of the gaze eye and strabismus at the same time each perceptual piece, health glasses barrel placed in the 00 position, and then turn the oblique glasses barrel, so that the two eyes picture overlap, at this time the barrel refers to the degree that the main perception of oblique perspective. If the light source of the two barrels is switched on and off alternately, and the barrel is moved until the reflective point is located in the center of the cornea, and the two eyes do not move, the degree at this time is the other perceptual oblique angle.