[Should accommodative strabismus be operated on?].

Abstract

Hypermetropia is probably not the real cause of accommodative squint. The arguments for this view are the absence of binocular vision in more than half and of the presence of a vertical deviation in about one third of cases of accommodative strabismus. Furthermore, after reduction of this vertical deviation by means of simultaneous surgery upon the horizontal and oblique muscles, binocular vision recovers spontaneously, the accommodative component of the squint disappears and visual acuity improves without glasses. Recent neurophysiologic research explains the beneficial effect of simultaneous surgery. According to these investigations there are two systems of accommodation and convergence; a quick phasic one, where accommodation is linked with convergence and a slow tonic one without interaction. The tonic system is responsible for the neutralization of the excess of convergence induced by hyperaccommodation. Tonic vergence depends on fixation disparity which is eliminated by a vertical deviation and restored by the surgical reduction of this vertical deviation. The fact of wearing positive correction produces and consolidates a hypo-accommodation, revealing a latent hypermetropia which could compromise emmetropisation. Furthermore, this correction being associated with squint, is a source of psychological complexes and the cost of an optical treatment is high, considering that spectacles need to be renewed frequently and many times during lifetime. On the other hand, simultaneous surgery removes an important obstacle to fusion and makes the patient independent of spectacles, not only regarding the squint, but also visual acuity.