Minimally Invasive Strabismus Surgery

6.1 Introduction

In October 1839, only a few days apart, two surgeons independently performed the Þrst documented successful myotomy to improve strabismus. In Berlin, Johann Friedrich Dieffenbach myotomized one medial rectus muscle in an esotropic boy while Florent Cunier of Brussels myotomized one lateral rectus muscle to cure an exodeviation [29]. Probably, already in 1818, William Gibson of Baltimore had myotomized several patients. However, because of the disappointing results, he failed to report it until 1841. Since these early beginnings of strabismus surgery, many different operating techniques for rectus and oblique eye muscles have been described, making surgical outcome more predictable. This chapter is devoted to minimally invasive approaches to strabismus surgery. All techniques being reviewed aim to reduce tissue traumatism, postoperative patient discomfort, hospital stay and working disability. For such techniques it is advisable to use the operating microscope which will allow higher magniÞcations than magnifying spectacles. A better view of the operating site allows a less traumatic tissue dissection and a better control of bleeding. Chemodenervation therapy, which can also be considered a minimally

1 The author has no Þnancial interests in any of the products mentioned in this chapter.

D. S. Mojon

Department of Ophthalmology, Kantonsspital St. Gallen, Rorschacherstrasse, 9007 St. Gallen, Switzerland e-mail: daniel.mojon@kssg.ch

invasive procedure, will not be appraised since excellent literature on that topic already exists [1, 18Ð20].

6.2 Nonsurgical Treatment

A nonsurgical treatment remains less invasive than minimally invasive surgery. Even if this seems obvious, strabismus surgery is indicated only if all nonsurgical options have been considered and potential alternatives have been tried. As nonsurgical treatments are beyond the scope of this book, only some key points that have to be tried before considering surgery will be mentioned. First, patients with visible strabismus, with no chance of postoperative binocular vision, should try to wear glasses. This may sufÞce to distract. However, glasses must be carefully selected. Exodeviations are accentuated by horizontally narrow glasses and esodeviations by horizontally wide glasses. Thus, horizontally narrow glasses should be tried for esotropia and horizontally wide glasses for exotropia. This is the only option for patients with disturbing pseudostrabismus, apart from lid surgery to change the amount of visible sclera. Second, a preoperative automatism should be developed to look for symptoms and signs of ocular myasthenia gravis and endocrine orbitopathy. In ocular myasthenia gravis patients, strabismus surgery is indicated only if medical treatments fail. In patients with endocrine orbitopathy, orbital decompression has to be considered, because usually strabismus surgery is advisable only afterwards. For both diseases, squint angles should be stable before strabismus surgery can be performed. Third, in all phakic patients a cycloplegic refraction is needed, regardless of their age. Patients with dark iris require the use of atropine. A prescription of the correct glasses or contact lenses may eliminate