FEB 24, 2012
Burton J. Kushner, MD, discusses the paradox of surgeons obtaining good results treating A- and V-pattern strabismus, convergence insufficiency and convergence excess esotropia using methods of insertion slanting recessions or biased resections that are opposite in nature. He reviews the underlying assumptions made to justify these approaches, previous publications on this topic and extraocular muscle mechanics. He concludes that most likely the recession or resection itself affects the outcome, and insertion slanting does not have a substantial effect.
He says that some researchers report success treating a V-pattern esotropia by recessing the medial rectus muscles and slanting the superior pole of each muscle back farther than the inferior pole (the Simonsz/von Graefe method), while others slant the inferior poles back farther (the Bietti method).
"The fact that essentially opposite approaches could produce good results presents a conundrum that challenges our basic understanding of eye muscle physiologic features and strabismus surgery," he writes.
While he believes that the Simonsz/von Graefe method is based on sound concepts of oculomotor mechanics, he says its effect is miniscule and negated by sarcomere remodeling, with the main effect coming from the recession or resection.
On the other hand, he says the published reasoning in support of the Bietti method is based on misquoting and misinterpretation of previous work by Alan Scott, MD, and does not make sense given what is known about oculomotor mechanics. In this case, Dr. Kushner concludes that the recession or resection procedure probably works despite the slanting.