When you have long sight you can see things a long way away clearly. But the problem comes with looking at things that are near, such as reading a book: the print appears blurred. One of the reasons this happens is that in long-sighted people - the eyeball becomes squashed. This pushes the focal distance beyond the retina, where it should focus. So the image on the retina is blurred. The solution is to insert a converging lens, that is glasses, in front of the eye. This will adjust the focal length so that the focal point hits the back of the eyeball, the retina. Then the image will be clear.
Long sight, the pont of focus is beyond the retina.