Strabismus update

At a meeting, earlier this year, of the American Association of Pediatric Ophthalmology and Strabismus (AAPOS), a number of new treatment options were introduced to the delegates, including two new surgical approaches and an innovative new therapy.

N. Ela-Dalman and colleagues from the Jules Stein Eye Institute, University of California, Los Angeles, California, USA, reported a new technique, to weaken the inferior oblique muscle (IOM) for the treatment of persistent or recurrent inferior oblique overaction. Patients underwent inferior oblique orbital fixation in which the insertion of the muscle was sutured to the lateral orbital wall. The authors discovered that this significantly weakened the IOM function. Patients with a V-pattern improved from a mean of 22.2 prism dioptres preoperatively to 5.6 prism dioptres postoperatively, while those patients with inferior oblique overaction improved from +2.6 overaction, on average to -0.3 dioptres postoperatively. The great advantage of this procedure is that it is, theoretically, reversible and so could potentially be converted to another weakening surgery, if required.

Bisen Gokyigit and colleagues have tried a new method of recessing the IOM without altering the position of the lower eyelid. The technique involved separation of the external 10% of muscle fibres with their associated anterior ciliary vessels from the internal 90% of muscle fibres. The external fibres, with their attachment to the lower lid retractors, were left in place while the internal fibres were disinserted and recessed. Retraction of the lower eyelid was not observed in any of the patients undergoing this new surgery, despite recessions being generally larger than those in conventional surgery. A further advantage is the sparing of the anterior ciliary vessels of the recessed inferior rectus muscle, which reduces the risk of anterior segment ischaemia.

Elsewhere, Linda McLoon, PhD, and her colleagues from the Department of Ophthalmology, University of Minnesota, USA, reported on the effect of insulin-like growth factor (IGF-1), administered locally, to strengthen extraocular muscles. IGF-1 is a myogenic growth factor that occurs naturally during the development and regeneration of muscles. The researchers tested the use of a slow-release pellet containing IGF-1 implanted on the scleral side of one superior rectus muscle in a rabbit model. One to two months after implantation, it was found that the treated muscle fibres were larger in cross-sectional area than control muscles and the force generated was significantly greater than that of the contralateral untreated superior rectus muscles. This treatment presents the possibility of strengthening extraocular muscles without the need for surgery.