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The author of this monograph is associated with the Ophthalmology Branch of the National Institute of Neurological Diseases and Blindness at Bethesda, Maryland. He has applied mathematical procedures to study correlations between the optical elements as the basis for a theory of ametropia. Purely statistical approaches, emphasizing distributions rather than correlations, generally have failed to yield significant clues as to the causes of ametropia. Van Alphen's approach strongly suggests that axial length is the most important factor. He presents laboratory evidence (strain-gage studies of scleral and choroidal stress, and pressure differentials between suprachoroid and intraocular spaces) that the axial length is determined primarily by ciliary and choroidal tension. He proposes that this tension varies in the same and in different eyes in attempts to "emmetropize" hypermetropic and myopic tendencies. Van Alphen postulates that choroidal tension influences axial length of the globe by forming a barrier between the intraocular hydrostatic pressure
Hill RV. On Emmetropia and Ametropia (Supplement to Ophthalmologica, Vol. 142).. Arch Ophthalmol. 1962;68(3):438. doi:10.1001/archopht.1962.00960030442022