The causes of cross-eye in one-month-old babies include physiologic and pathologic (e.g., internal strabismus) causes. 1. Physiological causes: one-month-old babies with rooster eyes, that is, eyeball cohesion, if there is no other discomfort, generally belong to the normal phenomenon. It may be caused by physiological reasons such as incomplete development of the baby’s eyes, and generally after the eye muscles are fully developed, it may gradually improve. 2. Pathological causes: the baby’s eyeball coalescence may also be caused by congenital strabismus, also known as infantile strabismus. Children may have a family history, the onset of the disease is common at birth or within 6 months after birth, and the angle of strabismus is large and stable. The etiology of the disease is unknown, and early surgery is required, usually before the age of 2 years, while both eyes are still developing and have the potential to achieve normal visual function. It is recommended that children with anomalous eye position should be seen promptly for evaluation of their condition and regular treatment under the supervision of a physician.