bates method: vision under adverse conditions a benefit to the eye?

[qergergergqe]

What does bates mean that not light but darkness is danger to eyes? how can the dark be danger to your eyes?? william bates said that reading in moving cars is beneficial to eyes, but how? bates also said lying down and reading is beneficial to eyes, but how? and then bates also said vision under difficult conditions is good mental training, but how?
also what is Photographic Type Reduction? bates said if can read Photographic Type Reduction, then your vision are benefited.