A 16-year-old boy visited our clinic for diplopia after the removal of a brain tumor. The patient described difficulty reading: words such as “happy” would become “happpy.” There was no prior history of strabismus or amblyopia. Three years prior, he was diagnosed with a suprasellar germinoma for which he underwent craniotomy to excise the tumor, followed by radiotherapy. His BCVA was 0.2 in the right eye and 0.05 in the left eye. Fundus examination revealed bilateral diffuse optic atrophy, and VF examination showed bitemporal hemianopia and an inferonasal defect in the right eye []. Hirschberg testing revealed 15° of XT in the left eye, and the prism-cover test demonstrated approximately 30 PD XT. On the prism-adaptation test, he reported a narrowing image with a 35-PD base in prism while a widening image with a 25-PD base in the prism. He noted the most normal image with a 30-PD base in the prism. Ocular-motility testing revealed normal duction and version. To eliminate the diplopia, we performed LRM recession of 6.0 mm and medial rectus muscle (MRM) resection of 4.5 mm in the left eye. One month after surgery, prism-cover testing revealed residual 14 PD XT. Prism adaptation for challenging with a 14-PD base in led to image narrowing. He was free of diplopia at both near and distant fixation without any prism aid. The vision and eye position remained stable at 5-year follow-up.
A 22-year-old male patient visited our clinic complaining of diplopia after a traffic accident 1 year prior. There was no abnormal eye position noted before his accident. The trauma caused encephalomalacia and fracture of the frontal bone and orbital bone. His best-corrected visual acuity (BCVA) was 1.0 in both eyes. Fundus examination revealed bilateral bow-tie shaped optic atrophy. His VF examination showed complete bitemporal hemianopia []. Traumatic optic chiasmopathy was then diagnosed. Ocular motility testing revealed no ophthalmoplegia, and the prism-cover test demonstrated 16 prism-diopter (PD) exotropia (XT) and 7 PD right hypertropia (RH). To eliminate this diplopia, we performed lateral rectus muscle (LRM) recession of 6.5 mm and superior rectus muscle (SRM) recession of 3 mm in the right eye. Three months after strabismus surgery, the prism-cover test revealed 0.5 PD XT and 4 PD RH at the primary position. Eye-alignment examination with the Hess chart also showed improvement over the preoperative findings. However, the patient complained that his diplopia persisted and failed to fuse with any prism.