Spontaneous reversal of vertical diplopia in graves' Eye disease

Two patients, among 77 examined in the past five years with Graves' eye disease and vertical diplopia, spontaneously resolved their vertical deviation. One had a maximum of 33 prism diopters of hypotropia decreasing to 1 prism diopter of hypophoria in 22 months, and the other a maximum of 12, improving to orthophoria in ten months. Ten mechanisms are considered. Five seem compatible with the findings of each of our two patients: reversal of a hormonal effect causing intracellular deposition of mucopolysaccharides, lengthening of the involved muscles from being chronically stretched, hypertrophy of the antagonist of the restricted muscle, resolution of abnormal co-contraction of the involved muscle when it was functioning as an antagonist, and reversal of fast calcium channel problems affecting muscle relaxation. No mechanism is proven to be the operating one. This report emphasizes the importance of delaying strabismus surgery in patients with Graves' eye disease until the motility findings are unchanged for a year.