Oxygen nuclei irradiation of retinas: long-term observations

Delayed (4.5 years postexposure) retinal effects from corneal exposure to stripped oxygen nuclei accelerated to particle energies of 250 or 300 MeV/nucleon are reported. The left eyes of six rhesus monkeys were subjected to beam fluxes ranging from 1.3 x 107 to 3.2 x 108 particles/cm2 with right eyes serving as controls. The retinal doses for those fluxes were estimated to be between 150 and 4200 rad, respectively. No discernible retinal lesions were observed in two monkeys receiving 150 and 160 rad. A third monkey exposed to a medium flux of 5.4 x 107 particles/cm2 (710 rad) exhibited ultrastructural changes in all retinal layers considered to be primarily secondary to vascular damage. Lesions in the remaining three monkeys subjected to fluxes ranging from 2.3 x 108 particles/cm (2700 rad) to 3.2 x 108 particles/cm (4200 rad) were more severe with varying loss and disorganization of retinal structures