Abstract
Purpose: :
Thyroid orbitopathy (TO) is the most common cause of restrictive strabismus. Patients often present with vertical and/or horizontal double vision due to restriction involving most commonly the inferior and medial rectus muscles. Traditional muscle surgery involves release of the tight muscles. Previous literature has described frequent need for secondary operations and over correction incidence of up to 50%. Recognizing that the tight muscles are also limited in their excursion; it was proposed that operating on the better moving eye particularly the inferior oblique (IO) might produce an improvement in binocularity and decrease the incidence of over correction.
Methods: :
A total of 42 patients with restrictive strabismus due to TO treated at the University of Virginia over 12 years with inferior oblique surgery were retrospectively reviewed.
Results: :
Thirty nine patients were treated initially with inferior oblique surgery. Of these 28 patients required secondary procedures. Four patients were over corrected and a total of 24 patients were under corrected. A total of 3 patients were treated with IO surgery as a secondary procedure. Five patients were treated with additional muscle procedures at the time of IO surgery (3 medial rectus (MR), 1 superior rectus (SR) and 1 lateral rectus (LR)). At the time of last follow up ranging from 6 months to 8 years 23 had no diplopia, 2 had minimal diplopia and 2 had persistent diplopia. All but two were completely functional.
Conclusions: :
Inferior oblique surgery by balancing the overall excursion of extraocular muscles in thyroid patients may produce binocularity in primary position and down reading gaze. There appears to be an increase in the area of binocular single visual and a decrease in the incidence of over correction with the use of inferior oblique surgery. The use of the Hess screen and binocular single vision fields is helpful in assessment and planning of surgery in these patients.
Keywords: strabismus: treatment • orbit • eye movements