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 10-year-old boy was referred to our clinic with the complaint of diplopia. He described a vertically displaced image that disappeared with chin-up posturing. He noted this vision change after cranial surgery for removing a craniopharyngioma 4 months prior. His preoperative ophthalmic examination was normal except for bilateral myopia. Cycloplegic refraction revealed − 2.50 diopters in the right eye and − 2.00 diopters in the left eye. Both eyes had a BCVA of 1.0. Prism-cover testing showed 11 PD XT at the primary position. Ocular motility testing revealed normal and symmetric eye movement bilaterally; however, the Hess chart demonstrated mild supraduction overaction in the right eye. Fundus examination revealed bilateral optic atrophy, and VF examination showed bitemporal hemianopia []. Since the patient could eliminate the diplopia with an adapted head posture, we proceeded with observation only. One year later, the patient noticed diplopia only with an upward gaze. The Worth four-dot test revealed left-eye suppression. The last follow-up was 6 years after the first visit, and the optic disc, VF defect, and XT remained stable. His BCVA was 1.0 bilaterally with a correction of − 4.75 diopters in the right eye and − 4.00 diopters in the left eye. The patient admitted that he seldom experienced diplopia and could simply ignore it when it occurred.