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In 40 patients with metastatic brain tumor and acute lymphoblastic leukemia received whole brain irradiation, the dose delivered to the eyelens was measured using T.L.D. chips applied on the eyes as usual shield. The dose to the eyelens was expressed the relative dose to the mid brain dose. Radiotherapy was administered using Co-60 teletherapy with bilateral whole brain irradiation. The results are as follows: 1. The dose to the right eye from its incipient field is 16.6% of tumor dose while the dose to the same eye from the opposite field is 41.2%. On left eye, 19.2% from incipient field while 39.2% from the opposite field. 2. Total received dose to right and left eyes is 28.9%, 29.8% of tumor dose respectively. 3. Comparing lens shield group with orbit shield group received dose is 22.5%, 15.8% of tumor dose, respectively. 4. The dose delivered to the eyelens in ipsilateral side depends upon internal scattering, location of lead shield and penetrating dose of lead in itself. The dose in contralateral side depends upon divergency of radiation beam and patients’s malposition. 5. The dose to the eyelens should be less than 10% of tumor dose with adequate shield, also not missing the chance of leptomeningeal recurrence because of overshielding.
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