Is combined surgical correction of horizontal and vertical squint of value in Graves' ophthalmopathy?

Background: In Graves' ophthalmopathy squint can be corrected in about two-thirds of the patients with a single recession of an inferior or medialis rectus muscle. The dose-effect correlation is linear over a wide range. Combined vertical and convergent misalignments are rare. The aim of this study was to evaluate the dose-effects in combined recessions of medialis and inferior rectus muscles. Material and Methods: The dose-effect of combined recessions (one side medialis and inferior n = 28, both sides medialis and one side inferior n = 9) was evaluated. The control groups were patients with Graves' ophthalmopathy, who had single inferior recession (n = 187), single medialis recession (n = 37) and bilateral medialis recession (n = 44). Results: Small hypotropias (up to 5degrees) at the eye with the poorer abduction disappear after single (17 of 21) or bilateral (14 of 19) medialis recessions. This obvious influence of horizontal recession on the vertical angle leads to a higher dose-effect for the inferior recessions in combined surgery, and was stronger for bilateral cases (from 2.0degrees to 2.7degrees/mm recession) than for unilateral cases (from 2.0degrees to 2.2degrees/mm recession). The dose-effect for medialis recession in combined surgery increased for the unilateral procedures only from 1.7degrees to 1.8degrees/mm recession and not for the bilateral medialis recession. Conclusions: The dose-effect for combined medialis and inferior recessions is enhanced and varies to a much higher degree in comparison to single muscle recessions. Because of the higher variability, patients who need both medialis and inferior recession should be better operated in separate sessions, beginning with the horizontal muscle(s).