Simply put, “strabismus” is a condition in which the visual axes of both eyes are not parallel. If the degree of non-parallelism is obvious, as shown in the picture, it is easy to detect. Sometimes, however, the patient’s strabismus is so small that it is not easily detected in normal life, or it is only intermittently detected. Often patients or parents of patients ask, “It’s okay to have a small degree of strabismus, right? It doesn’t need to be treated, right?” First of all, let’s talk about how our eyes keep the visual axes of both eyes parallel and strabismus does not occur. This is because our brain has a fusion function that can adjust the skewed object image to the macular central recess of both eyes, and this adjustment ability is called fusion ability. People who have poor fusion or whose fusion ability decreases with age are prone to develop a skewed eye position, or strabismus. Small strabismus, although it has little impact on aesthetics, may have the following hazards that need to be taken seriously: 1. For high and low strabismus, it is difficult to fuse even just 1 or 2 degrees, which can lead to severe visual fatigue symptoms in patients. Eye pain, headache and even nausea, vertigo, insomnia, etc. can occur. Therefore, even a small degree of strabismus should be taken seriously and treated promptly!