|MadSci Network: Anatomy|
Dear Shaf Hussain,
You have asked an interesting question. According to the text Ocular Pathology by D. J. Apple and M. F. Rabb (Mosby, 1985) the diameter of a newborn's eyeball is about 18 mm; it increases rapidly during the first year of life, but after this, growth is very slow. The reasons behind eyeball growth are not precisely known. This was discussed in a great book by Richard J. Goss called The physiology of growth (Academic Press, 1978, pp. 191-199). Eye growth in a developing chick can be diminished by introducing a small tube into the eye to drain off intraocular fluid and reduce intraocular pressure (AJ Coulombre, Journal of Experimental Zoology, vol. 133, pp. 211-225, 1956 "The role of intraocular pressure in the development of the chick eye"). When this is done, the eyeball fails to enlarge normally, but the retina nevertheless keeps on growing, so that by the time the chick is ready to hatch from the egg, the eyeball is smaller than normal, but the retina has enlarged to form a highly folded sheet of neural tissue crowded within the eyeball. Lower animals such as fish apparently are able to enlarge their eyeballs and retinas steadily over the course of their entire lives, but this ability is lost in mammals and birds.
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