A 400-degree increase in myopia after retinal detachment surgery is normal if an extrascleral cerclage was performed, and is usually considered abnormal if a vitrectomy was performed. Retinal detachment requires surgery. There are several types of surgery, the two main types being an extrascleral ligation and a vitrectomy. Extrascleral ligation causes the patient’s eye axis to lengthen, which can lead to an increase in myopia, and a 400-degree increase in myopia after surgery is normal. Vitrectomy surgery itself does not change the refractive status of the patient. If silicone oil is injected into the eye during the surgery, it will lead to hyperopia rather than myopia. Therefore, a 400-degree increase in myopia after vitrectomy surgery is not normal. To determine whether an increase in myopia after retinal detachment surgery is normal or not, it is recommended that you seek medical attention in a timely manner and ask your doctor to make a professional judgment.