Recently, some diligent researchers have come up with a novel explanation of myopia progression in the human, i.e., the "peripheral hyperopic defocus".
In plain English, it means when you wear glasses to correct nearsightedness or more accurately the central vision, the side vision is actually still fuzzy with the clear focal points behind the eye (or being hyperopic, i.e., farsighted, by definition). This is illustrated in the picture here, in which the white arc behind the eye is the hyperopic focus. It is this blurriness at the retinal level that seems to cause the eyeball to grow or "elongate" in the anterior-posterior sense. Not only in the myopic eyes, potential myopic eyes also have the more prolate eyeball shape. So it would appear that the shape of the eyeball is predictive of myopia formation and progression.
With the new information,
(1) the instrument makers can develop new refractive devices;
(2) lens makers can design new spectacle and contact lenses;
(3) the doctors will have new myopia managing regimens to contemplate;
(4) the biochemists will propose and test new projects on the development of posterior sclera/choroid during myopization; and
(5) the drug makers can look into more targeted posterior pole growth inhibitors.
In other words, a whole new enterprise unveils right before our eyes. Naturally it remains to be seen if this defocus theory ultimately proves to be true.