The early reactions of the eye to radiation are conjunctivitis and, with higher doses, corneal damage. The inflammatory reactions are transient and remit within a few weeks after the end of radiotherapy. Doses above 60 Gy can produce corneal ulcerations with the risk of perforation and loss of the eye. The most frequent late reaction of the eye is cataract of the lens. The tolerance dose (about 5 Gy) is extremely low and the latent period varies from 6 months to 3 years. The lens in children has a much lower tolerance. The increasing potential for optical support and ophthalmic surgery over recent decades has reduced the fear of this complication. The most severe late complications are retinopathy (RR) and neuropathy of the optic nerve (RON), both of which are caused by radiation-induced microangiopathy. Visual loss is very frequent and complete blindness is seen with high doses in the range of 50-60 Gy. The latent period of these injuries varies widely from 1 month to 15 years, but they usually occur within 3 years of treatment. Conflicting frequencies are reported in the literature. Beyond 30 Gy, usually no RR is seen. However, the lowest recorded dose producing RR is 11 Gy. In the high dose range of 60-70 Gy RR and RON are found in 10%-100% of patients. There is a great need for prospective trials to estimate the true risk to patients with nasopharyngeal, maxillo-ethmoidal, and orbital tumors, pituitary adenomas, and tumors of the salivary glands. To minimize complications of radiotherapy to the eyes daily fractions should be reduced to 1.7-1.8Gy.(ABSTRACT TRUNCATED AT 250 WORDS)