IGF1 and Strabismus: Recent studies demonstrated that insulin-like growth factor-1 (IGF-1) applied unilaterally over a 3 month time-period to infant monkey medial rectus muscle resulted in development of strabismus,8 while BDNF treatment did not.7 However, analysis of the effects of sustained release of BDNF showed that there was a significant effect on the myofibers that expressed the slow myosin heavy chain isoform (MyHC).