The neutral eye, when fully relaxed or flattened, is set to focus distant objects. Rays of light emanating from objects farther than 20 feet are considered to be parallel, and parallel rays or bundles of rays of light will focus on the retina of a neutral eye without change or effort. Should the object be nearer than 20 feet, then a bending of the eyes must take place in order to see objects clearly. Distant vision for neutral eyes is 20/20 (ability to read on a chart, line 20 at 20 foot distance) or better.
At 40 inches from the eyes, neutral eyes have to bend or add 1.00d. of curvature to the eyes. At 20 inches 2.00d. -- at 13 inches, which is the reading distance, neutral eyes have to bend and add 3.00d. of curvature to the eyes. At 10 inches it is 4.00d., at 4 inches it is 10.00 d. At 2 inches, a person with neutral eyes would have to bend and add 20.00d. of curvature to his eyes. A watchmaker's loop, which he wears all day long on one eye, has a plus 20.00d. spherical lens.
A plus lens will blur the distant vision of a neutral eye, but it would reduce the bending of the eyes for near work. At 13 inches, which is the reading distanc, neutral eyes wearing plus 1.00 spherical glasses would have to bend their eyes only 2.00.d. instead of 3.00d. It would be a big help to a person who has to read a long time. But, for distance he would be able to see much better with the naked eyes. When age sets in and the bending of the eyes becomes difficult, the wearing of a pair of plus 1.00 glasses, for near work, becomes a necessity.
It would do much good and no harm to children or adults who have neutral, perfect and normal eyes, to wear plus spherical glasses up to plus 1.00d. whenever they do sustained and prolonged near work. It would lessen the bending of the eyes in looking near and downward. It would fully relax and stretch the eyes in trying to see far and upward. It would lessen the chances of their eyes becoming poor-sighted, near-sighted and astigmatic.