Relative hypermetropia: a conception of Donders fallen into oblivion.

Donders created 2 triads in connection with hypermetropia. The first is well known: Ht = Hm + H1. The second is a division into facultative, relative, and absolute hypermetropia. In present ophthalmic literature the second triad is confused with the first; the important member called relative hypermetropia is not even mentioned. I tried to find the cause of this misunderstanding. In my opinion the second triad--in the form Hess had given to it--should be placed among the basic informations of ophthalmology.