Long distance visual effects
Flash Blindness, also referred to as "dazzle," is a temporary impairment of vision. Victim does not have to be looking directly at the source for this to occur.
Nighttime greatly increases distance of effect
Retinal burn: visual capacity is permanently lost in the burned area. Retinal burns can be produced at great distances from the nuclear detonation because the probability of occurrence does not follow the inverse square law as is true of many other types of nuclear radiation.