The eye shape is born to be what it is like. Generally, the shape will not change in essence with time flying. Sometimes people think their eyes look different than before because there are some factors of alteration. First, even the shape will no change, the size will change. The size of eyes refers to the size of palpebral fissure, which means the distance between upper and lower eyelids. When people grow old, their faces grow too. Thus, palpebral fissure becomes bigger. Meanwhile, the location of eyes in a face is also different. For infants, their eyes are almost in the middle of face, but for adults, there eyes are at about one third of face. So, eyes look different. Additionally, there will be some trace of age leave around your eyes, such as extra fat and wrinkles. They may bring you eye bags or black circles. They may squeeze your eyes and make them look smaller. All in all, this is no natural way to change the shape of eyes, it comes from gene. If you have to, plastic surgery is an option.
Technically, our eye shape are born. It is not possible to alter the shape of your eye without doing serious damage. But aging can make "change" your eye shape. As people getting old, it will appears wrinkles and get skin hung around the eyes. That is why make other think your eyes shape changed. Anyway, this is the natural rule that we can hardly prevent it.
It's hard to say. Because someone will never have change on eye shape until sixties, while others may be change gradually with age. No matter what situation you are, in fact, your eyes will be narrow and small in your old ages eventually. All in all, eye shape change depends on personal body qualities.