Retinoblastoma is the most common intraocular tumor in children. External irradiation is no longer the treatment of choice for retinoblastoma because of the risk of cosmetic dysplasia and tumor induction associated with radiation therapy. Modern radiotherapy techniques have reduced the dose of irradiation to normal tissues, and the value of external irradiation for retinoblastoma needs to be newly recognized. (1) External radiation therapy is increasingly becoming a salvage treatment for retinoblastoma after failure of chemotherapy combined with local therapy. Kaan [6] reported that 27.4% (26/95) of the 95 patients treated with adequate chemotherapy received external irradiation. The eye was preserved in 76.9% (20/26) of those who received external irradiation. In the whole group, 21.7% (15/69) of patients with stage I-IV received external irradiation and 30.6% (11/36) of children with stage V received external irradiation. In stage V, 36.1% of those who received external irradiation retained their eyes. 32 cases of failure after chemotherapy were reported by Chan [7] to receive crystal reduction radiotherapy and 4 cases received total eye irradiation. The ocular retention rate was 83.3% (30/36). (2) Chemoradiation therapy combined with prophylactic external radiation radiotherapy Stage E tumors are difficult to control with chemotherapy alone. For children with stage E in both eyes and children with stage E in which the contralateral eye has been removed, it is desirable to preserve the eye with vision. Shields [8] reported on a study of stage E retinoblastoma in which patients with stage E in the contralateral eye and contralateral eye removal received prophylactic radiotherapy after chemotherapy. It was performed 2 months after chemoablative treatment when there was no sign of tumor recurrence. Sixty-four patients received chemoablative therapy and 12 patients received chemoablative therapy combined with prophylactic radiotherapy. At 5 years of follow-up, 48% (20/42) of those treated with chemoablative therapy and 80% (4/5) of those treated with combined radiotherapy retained their eyes. The results showed that chemotherapy combined with prophylactic radiotherapy could reduce the need for curative radiotherapy and eye removal compared with chemotherapy alone. 2.Modern precise radiotherapy technology: With the advancement of computer technology and the development of imaging, radiotherapy has gone through the stage of body surface anatomical localization, bone anatomical localization, and developed into the era of localization, planning and irradiation based on three-dimensional image reconstruction. (1) Classical single field radiation therapy: The anterior border of the classical single temporal side irradiation field is in front of the serrated edge, i.e. the irradiation range is the whole retina. However, the irradiation range is actually the range of the 50% isodose curve, not the range covered by the prescribed dose curve. The conventional single temporal field approach is not suitable for advanced tumors that require irradiation of the entire retina or posterior chamber. The single anterior electron beam irradiation technique allows complete coverage of the entire eye including the anterior and posterior chambers. However, when the irradiation dose exceeds 40Gy, the corneas, crystalline lenses and other ocular tissues are irradiated with the prescribed dose, and the complications of radiation keratitis, cataract and glaucoma increase. (2) Stereotactic radiotherapy: stereotactic radiotherapy is the directional collimation of radiation from different directions to irradiate the lesion, with the tumor receiving a high dose of focused irradiation and the surrounding normal tissues being relieved of irradiation. sahgal [9] reported 5 patients receiving stereotactic fractionated radiotherapy with a median follow-up of 46.5 months. The tumor volume was exenterated by 1 mm as the treatment target area, which was achieved by irradiation with 4-5 non-coplanar focusing rotational arcs and a 10-20 mm diameter circular collimator. The prescribed dose was 40 Gy/20 times, and the prescribed dose curve was 90%-95%.