It seems like being nearsighted for much of your life due to elongated eyes would make it easier in general to focus on near objects rather than far since the lens would not have to change much. Since in old age we lose the ability to focus close images due to a hardening of the lens over time, wouldn't having eyes shaped more for near images be helpful in maintaining the ability to see close up, and thus nearsighted, or myopic people, would be less likely to develop farsightedness, or hyperopia, with age? It seems then that nearsightedness is more of an adaptation that occurs at a young age, so that these people can work up close for longer periods of time both in the the short term(studying) and long term(age). I'd love to hear if any research has been done on this subject, and any other input you have.
2 Answers
It is generally understood that we tend to become hyperopic as we age (reference). As to whether this aids in decreasing myopia is stated as marginal in papers. One paper titled "Is there a hyperopic shift in myopic eyes during the presbyopic years?" states that
it was found that almost all hyperopic and emmetropic eyes showed an age-related hyperopic shift; but only a small proportion of myopic eyes shifted toward hyperopia, with others remaining relatively stable and still others increasing in myopia.
In a second study titled "Age-Related Decreases in the Prevalence of Myopia: Longitudinal Change or Cohort Effect?", it was found that there is a decline in the prevalence of myopia in older adults.
Some people in personal experiences have stated that their myopia has decreased (reference) while others found themselves wearing bifocals (reference). In closing, I would say that this is something that your Ophthalmologist may be able to predict better but it is not a given that your myopia would decrease. It may or may not be so with many factors like your eye shape coming into play.
Let me see whether I can explain this quickly. The eye size is tightly regulated genetically. Babies don't have big eyes, they have exactly the same sized eyes like adults, only their head is smaller. Myopic eyes are larger than normal and hyperopic eyes are smaller than normal, even though the difference is only 1 to a few millimeters. When you focus to the far point, the light focusses to the nearest point possible in the back of your eye. When you come closer to an object, the focus point inside the eye moves further out. Thus, the farsighted person with the small eye can only see when the object is away. Moving closer moves the focal point inside the eye to behind the retina. The opposite is true for myopic people with too large eyes. When a person gets old, the lens gets stiff and cannot adjust the focal point inside the eye to the distance of the retina. Thus, the lens remains stiff in the most relaxed state (extended), or - in other words - at the most distant focal point the person had when it was young. A normal-sighted person has his old-age focal point at the horizon and since his lens is stiff, can only see sharp from the horizon to a few meters in front of him (depending on the intensity and wavelength of the light - blue light better than red). A short-sighted person is of disadvantage when old, since his far point remains to be at short distance. He gains a little sharpness over the normal sighted person in the short distance, but loses it in the distance like he always did. You can calculate this nicely, actually. All physics.
