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 37-year-old woman developed diplopia after a second brain surgery 2 months prior, with left occipital craniotomy for recurrent tentorial meningioma removal. She had good vision and no strabismus before the first surgery for removing her brain tumor, 18 months previously. Diplopia and esotropia (ET) developed after her first brain surgery, although 10 PD prism glasses eliminated the diplopia in daily life. However, after her second surgery, she experienced diplopia even with the prism glasses. Ocular examination revealed a BCVA of 0.8 in the right eye with − 1.75-diopter correction and 1.0 in the left eye with − 1.75-diopter correction. Fundus examination revealed no optic atrophy, and VF examination showed new-onset right homonymous hemianopia []. Prism-cover testing revealed 25 PD ET at the primary position, with both near and distant fixation. Her eye movement was free and the range of eye movement was normal bilaterally. To eliminate the diplopia, we performed MRM recession of 7 mm in the left eye. One month after surgery, prism-cover testing revealed 8 PD ET. The patient was satisfied with new prism glasses.