POLG and Nystagmus: The phenotype of POLG‐related disorders is variable; it ranges from severe and often lethal childhood forms to later‐onset forms with a continuum of overlapping phenotypes, including ophthalmoplegia.113 In addition to ophthalmoplegia, ptosis, gaze‐evoked nystagmus, rebound nystagmus, abnormalties of saccades (dysmetria and slowing), and impaired pursuit have been observed.114 Treatment of mitochondrial diseases is still limited and includes vitamins and cofactors.21