Here is a brief explanation relative to the reason and the how. Let me know if there is anything that you do not understand. We have to be scientifically consistent with this so that we have a basis to work from that we know works in other aspects of light and life. In other words in order for this to work we have to do what science says induces light to arrive at a particular point and do what it does. The Bible is clear in stating that God is light.
Ancient writings speak of the single eye which is the light receptor of the body.
Back to quantum physics. When a light wave is observed it collapses to a microdot particle. Magnetism flowing down from above which can entwine with our DNA cannot reach its goal within us unless we watch ourselves and collapse that wave to a particle microdot. It then enters our body and entwines with our DNA and can correct the defects in our DNA and in the DNA of all life upon the planet. To confirm this fact go to any book store, pick up a book on quantum physics such as the Dancing Wu Li Masters and see how light waves that are observed collapse to a particle and then can hit their target.