Kettesy A
Klin Monbl Augenheilkd. 1979 Jan;174(1):41-4.
Author attempts to explain the rise of infantile convergent squint, when the hypermetropia is less than 3,5 diopter. In such cases the low hypermetropia is relative in the sense of Donders, because a sometimes isometropic aniseikonia prevents the fusion. To examine the aniseikonia he recommands a very simple procedure, the comparison test, carried out joined to the cover test.