Their influence on the photoreceptors generates chemical reactions that inform the brain via the optic nerve. Mercury rules the optic nerve and retina in general, but the Sun, Uranus and Neptune rule specific groups of cells. The Sun also rules the lens and cornea, while the Moon controls both the vitreous and aqueous humors. Since the different parts of the eye are nourished and maintained by the blood, it is most vital to keep it clean with good kidneys. When toxic blood goes to the eye, the aqueous humor loses its normal alkaline balance and can no longer absorb the above described highly charged etheric beam, then instead of building the eye, light gradually burns it and blindness follows.
Spiritual vision is an extension of physical sight.
If the concentration is used to investigate the memory of nature this beam is focused upon the planetary reflecting ether, then our one-pointed mind brings its vibration in harmony with the 4th Region of the World of Thought, then the heart, through right feeling lifts us up to the World of Life Spirit which is the true memory of nature. The Life Spirit, the World of Thought and the higher ethers are brought in unison by this process in a manner similar to the strings of a piano when you depress the pedal and hit a low C string, then the other octaves, middle C and high C resonate with it. Of course this all sounds simple, but one must work many lifetimes to attain the goal. Some of us DID start in the past and have attained some measure of insight. She trained herself with them and used most positively the last 15 years of her life in total blindness.