A Case of Highly Myopic Strabismus That Showed Temporary Large Exotropia After the Yokoyama Procedure

Highly myopic strabismus is a progressive form of esotropia and hypotropia. It occurs when the globe axis is elongated due to high myopia, causing the posterior portion of the globe to dislocate between the superior rectus and lateral rectus muscles and prolapse from the muscle cone. This condition is often accompanied by mechanical restrictions of eye movement. If it progresses, the globe may become fixed in an inferomedial position. The most common treatment is uniting the superior and lateral rectus muscle bellies using a suture posterior to the muscle insertions, also known as the Yokoyama procedure. This case report presents the case of a 59-year-old male patient who underwent the Yokoyama procedure. After surgery, the patient experienced severe inflammation and pain during eye movement; however, as the symptoms subsided, diplopia improved, and by the one-month follow-up examination, the pain had completely resolved. In addition, the patient showed a significant angle of exotropia, which spontaneously recovered to the normal position one month after the surgery, accompanied by the resolution of diplopia. When the patient underwent the Yokoyama procedure after seven years of observation following the initial examination, it was found that the patient had exotropia immediately after surgery, but the eye position improved over time, and the patient was eventually able to maintain a normal position. Postoperative magnetic resonance imaging (MRI) showed that the position of the superior rectus and lateral rectus muscles had improved, and the angle of dislocation had also improved. There have been no reports of spontaneous improvement in postoperative exotropia, as in this case, which provides new insights into the possibility of temporary changes in eye position and spontaneous improvement in the treatment of highly myopic strabismus. Additionally, it also prompts reconsideration of the importance and significance of postoperative management.