How: from memory: there is mention of a part of the eye becoming stretched due to weightlessness - you’d have to read the article I referenced and others I no longer have marked on the subject.
OT
Have you read “The Crystal Sun”? It is a fascinating bit of research on lenses. For instance: the best lenses made 3500 BC were not equaled in quality until 1900 AD. Most lenses made in antiquity are labeled jewelry by archeologists as “everyone knows” that eye glasses and telescopes were relatively modern discoveries. Get the hard back (British edition) since it has all the appendices where the history of some groups or particular lens is discussed of the thousands known to exist. Many illustrations.
But the article states the eye shortens.
Your distance prescription depends on the length of your eye. Your up close anility depends on the flexibility of the lens in your eye. It closes down enough to be relevant in everyone on the planet when they hit their every 40’s.
Have to check out “The Crystal Sun”. Cataract surgery has been done since the ancient Egyptians.