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 40-year-old man complained of diplopia 4 days after trabeculectomy of the right eye 4 months before visiting our clinic. His corrected vision was 0.5 with − 5.50-diopter correction in the right eye and 1.0 with − 3.50-diopter correction in the left eye. Fundus examination revealed enlarged disc cupping in the right eye and a normal left eye. His VF examination showed an extremely constricted VF in the right eye, with only 7.5° × 5° remaining in the central island []. Prism-cover testing revealed 20 PD XT at the primary position. Ocular motility testing demonstrated no ophthalmoplegia. To eliminate the diplopia, we performed a right LRM recession of 7.0 mm. One month postoperatively, prism-cover testing revealed 3 PD right hypotropia. The patient described alleviation in diplopia, although it did occur sometimes. He also reported improved stereoacuity.