There is a rule in ayurveda that states the sun can improve weak vision. Today is a sunny day in SF, so I tested this rule to see if it works. The morning started out with my usual double vision. So, I started doing garden work at the garden out in the sun. A few minutes later I noticed that the garden statues and ornaments in the yard started to look clearer. So, I drove my car to have lunch at an Indian restaurant a few blocks away and I could see well enough to drive through the streets fairly safely..
So, I learned that being out in the sun doing some activity is good exercise and necessary to maintain good vision. This principle ties in with a certain eye exercise to improve vision. The exercise is called the swing. It requires one to swing the body back and forth with the legs as the center or the fulcrum of the swing. This is supposed to improve vision which needs dynamic activity to engage the eyes with the environment. IOW, being in a static position is not good for clear vision. So, IMO the sun is good for vision since it encourages the body to move around and engage with the environment. However, the sun may not be as beneficial to lay outside to sun bathe. So there you have: the ayurvedic principle is very sound and practical.
