This report is intended to be used as an aid to military mission planners in determining allowable proximity to a nuclear fireball from the standpoints of permanent retinal injury and the temporary effects of flashblindness. Pertinent physical and physiological phenomena are discussed in moderate detail; the nucleaus of the work being a family of curves which indicate acceptable separation distances for the prevention of retinal burns and flashblindness. Detailed instructions for approximating acceptable separation distances using a slide rule are included as an appendix.