사시, or strabismus, is a condition where the eyes do not properly align with each other. This misalignment can cause one eye to look straight ahead while the other turns inward, outward, upward, or downward. It can occur in children and adults and may lead to issues such as double vision or difficulty focusing. Treatment for 사시 often includes options like glasses, eye exercises, or surgery, depending on the severity and underlying cause. Early diagnosis and intervention are important to prevent complications, such as amblyopia, commonly known as lazy eye, which can develop if the brain favors one eye over the other.