If your 16-month-old child has a watery eye, it is likely due to a viral infection, such as a cold that has spread to the eye. This usually clears up on its own within 5 to 7 days. You can gently clean the eye with a damp towel to remove any discharge. However, if the symptoms persist for more than a week without improvement or if other symptoms develop, it is advisable to consult a doctor.