Human eyes do grow, but most of the growth takes place early in life.
For the retina, a vast majority of growth takes place before the age of two.
For the eyeball, most growth occurs before the age of six, and there is supposedly no growth at all after puberty.
Nearsightedness, which is tied to an elongated eye shape, can appear relatively late, after growth is supposed to be done; the eye remains moldable and can change its shape.
Why changes in the relative dimensions of the eye should occur is not fully understood.
It is likely that the eye remains sensitive to growth factors, chemical signals that stimulate growth.
But the eye has many such growth factors, and which ones are at work in the development of the eye remains to be learned.