For the subject of refraction and refractive errors such as the
different forms of hypermetropia, myopia and astigmatism the reader
is referred to the many excellent works on ophthalmology which cover
these subjects quite thoroughly. They are only used here in the
relation to eye strain and its reflexes. The osteopathic logic here
given should be combined with a reading of the refractive errors in
such works as Fuchs, Weeks, De Schweinitz and others.