[The Leiden school].

Simultaneous horizontal and cyclovertical surgery gives better results than pure horizontal surgery; not only binocular vision reappears immediately and spontaneously but the accommodative component of the squint disappears as well. The question is to know why simultaneous surgery gives such good results. We think that the reduction of the vertical deviations associated with horizontal strabismus may give an explanation. In our experience, a vertical deviation is often present in accommodative strabismus and can disrupt fusion. The hemiretinal suppression which follows, puts the vergence system into open loop. The accommodative vergence caused by hypermetropia becomes manifest so that the correction needs to be reinforced frequently. In a young child this may impede the emmetropisation process. In addition, the spectacles being associated with strabismus, may be the source of psychological complexes. The fact that the squint is not cured and the deviation reappears without spectacles gives us the right to look for a more adequate remedy. The good results we obtained with simultaneous horizontal and cyclovertical surgery and especially the disappearance of the accommodative element encouraged us to operate accommodative strabismus.