It’s unusual to see a middle-aged person holding a book arm’s length in order to read the print, or struggling for some time to thread a needle. Both are signs of presbyopia, difficulty in focusing the eyes on close objects.
As we grow older, the lenses in our eyes lose their elasticity and ability to focus for near and distant vision. Most people notice this at about the age of forty, particularly when reading. The print becomes a little fuzzy and, instead of accommodating with our eyes, we tend to over the book or newspaper a little farther away. Before long, the focus becomes set at a more of less constant distance.
Some people find that they become near-sighted as they grow older They see things clearly close at hand, but distant objects blurred. The condition is known as myopia, which comes from Greek word meaning ‘to close the eye’ Myopic people develop the habit half closing the eyes, which gives them sharper vision. In myopia, the eyeball becomes too long from front to back, so that light from distant objects comes to a focal point before it reaches the retina. Instead of casting a sharp image, objects appear blurry. Near-sighted people often find that as they age they don’t need glasses for reading.
Far-sighted people have the opposite problem. Their eyeballs are too short from front to back. They see distant objects well, but the focal point of those nearby is behind the retina. Babies are born far-sighted. For three to six months their eyes don’t focus on close objects, and then for months they wander individually instead of working together.