Humans are adaptable. The refractive error distribution in the population of newborns is almost a normal curve. By the first grade the distribution has become leptokurtic with the great majority of the population falling within -0.5 and +2.00 diopters of error. The babies have grown out of their refractive errors!
Graduate Students at Indiana University did a study of babies at 2 weeks of age who performed as well on focusing tests as college students. The one baby who did not was about 5 D hyperopic. After 6 weeks or so it was clearly withdrawn and abnormal in personality. The baby could not respond to the test. Application of +4 D glasses changed the baby's personality overnight!
Regarding the overcoming of hyperopia by optometric intervention, the baby above was not followed, but if the baby continued to wear those glasses, now as an adult, he/she will still be +4 hyperopic.
I worked with an 18 month old esotropic girl whose eyes were so crossed I thought she had convergence fixus. However when I held her at arms length and turned my body through 360 degrees her vestibulars took over and her eyes straightened and she showed nystagmus. At each of the three visits I increased the plus to take home. Her eyes straightened with +11D. Then at the age of three years while moving to another city she lost her glasses and went without them for 3 months. The new eye examination showed her Rx to be +4. She had lost 7 diopters in three months!
I did not realize the significance and was not smart enough to say to Mom: "Let's leave the glasses off for another 3 months," or "Let's wear plano glasses with binasal occluders for 3 months." The last checkup of this patient was at age 18 years when she was wearing +4D contact lenses! We cured her of esotropia and reduced 7 diopters of hyperopia! She has of course continued to be straight eyed.
Wild monkeys have low hyperopia or emmetropia and no myopia. Caged monkeys have less hyperopia and much more myopia. Because the evidence for emmetropization is so strong, I suggest a couple of approaches on how to emmetropize young hyperopes.
We know that older people grow into myopia, so I would not put an upper age on when a person can grow out of hyperopia. The important condition is that they be able to intensively pursue visual tasks requiring accommodation. If they are not visually involved, and if we eliminate the need to emmetropize, they will not emmetropize!
When I'm in the mall, I see thick glasses on small children and I have to control myself. I know that wearing those glasses blocks emmetropization. If Mom would put the glasses on the child only in the afternoon, the child would grow out of his/her hyperopia and require several spectacle power reductions. If the child's correction is less than the refractive error, he/she will grow out of the need for those glasses and soon weaker lenses will be needed.