the pupil of the eye, such as at nighttime, will permit more light to enter and, although the retinal image size does not change, it can be relatively more hazardous. Also, it is assumed that any light gather- ing devices such as binoculars also would increase the hazard. Any lesions (damage) on the retina less than 50 microns in diameter probably would not be detected by an eye examination. Actual functional impairment of vision probably would not start to occur if the lesions were mild and less than 50 microns on the fovea - the most sensitive portion of the retina. There may be less injury to the retina of the eye if a given total amount of thermal energy is received at a slower rate, i.e., there is more opportunity for the adjacent cells in the retina to conduct away some of the heat. High yield detonations in the lower atmosphere do exhibit a slower rate of delivery than low yields (say, a million tons versus 20 thousand tons). However, high yield detonations (as well as low yield) at high altitudes show a relatively rapid rate of production of thermal energy. This, together with the fact that the thermal energy traverses less atmosphere in reaching the eye than from low altitude bursts, made high altitude and high yield bursts particularly troublesome. (Graphics No. 6) The DataThere have no recorded eye injuries to persons off-site. individuals have complained of temporary eye impairment. A few Four military personnel participating in the Nevada tests have received eye injury - 30.