Retinal Neuronal Loss in Visually Asymptomatic Patients With Myoclonic Epilepsy With Ragged-Red Fibers

Abstract

Myoclonic epilepsy with ragged-red fibers (MERRF, OMIM, #545000) is a rare neurological condition mostly caused by the m.8344A>G mitochondrial DNA pathogenic variant, which can variably affect multiple tissues, including the retina and optic nerve. We report detection of visually asymptomatic neuroretinal loss in 3 patients with genetically confirmed MERRF, using spectral domain optical coherence tomography (SD-OCT). All patients underwent a complete ophthalmic examination including assessments of visual acuity, color vision, pupillary reactions, extraocular movements, applanation tonometry, slit-lamp, and dilated fundus examinations. Standard automated perimetry or Goldmann kinetic perimetry was performed, as well as fundus photographs and SD-OCT of the optic nerve head and macula. Despite the absence of visual symptoms in all patients, and normal visual acuity and visual fields in 1 patient, the 3 genetically confirmed patients (point mutations m.8344A>G; age range: 18-62 years) with MERRF-related neurological manifestations, displayed thinning of the retinal nerve fiber layer and variable alterations of the macular ganglion cell complex. Visually asymptomatic patients with genetically confirmed MERRF can display features of structural neuroretinal loss, quantifiable with SD-OCT. Further investigations are needed to establish whether OCT can assess early neurodegeneration in MERRF.