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 32-year-old male patient with retinitis pigmentosa complained of intermittent diplopia for the past few years, with recent progression. His corrected vision was 0.8 in both eyes. Fundus examination revealed retinal pigmentory changes, narrowing vessels, and relatively pale discs bilaterally, and VF examination showed that only the central island remained bilaterally []. Prism-cover testing revealed 30 PD left hypertropia (LH) and 4 PD XT. Ocular-motility testing demonstrated slight overaction of the inferior oblique muscle and slight underaction of the superior oblique muscle in the left eye. On prism-adaptation testing, the patient reported no diplopia with a 16 PD prism. However, he did not like prism glasses and asked for surgical correction. We performed an inferior oblique myectomy in the left eye. One month after surgery, cover testing revealed 18 PD LH and 4 PD XT at the primary position. The patient experienced occasional diplopia only with right-up gazing, but there was no diplopia at the primary position or with near work. At the last follow-up visit 3 months later, prism-cover testing measurements were unchanged. The patient was satisfied with being free of diplopia in daily life.