Purpose: To report the serial evaluation of asymptomatic eyes of subjects with mutated G11778A mitochondrial DNA.
Methods: Forty-five asymptomatic G11778A Leber hereditary optic neuropathy (LHON) carriers and two patients with the mutation who developed unilateral visual loss underwent testing that included visual acuity, automated visual field, pattern electroretinogram (PERG), and spectral-domain optical coherence tomography every 6 months between September 2008 and March 2012.
Results: Visual acuity, visual fields, and retinal nerve fiber layer thickness remained stable within the normal range. Mean PERG amplitudes of carriers dropped progressively by ∼ 40% from baseline to 36 months. In addition, comparisons with the fellow eyes of patients with unilateral optic neuritis revealed a 3.4 ETDRS (Early Treatment Diabetic Retinopathy Study) letter loss in the LHON carriers. A single carrier developed visual loss, with PERG amplitudes dropping by half. In one of two LHON cases who presented with unilateral visual loss, visual acuity in the asymptomatic eye was ∼ 20/40 at baseline. The PERG amplitude of this eye was reduced to ∼ 30% of normal. Six months later, his visual acuity had dropped to ∼ 20/500. A second patient who was ∼ 20/20 and had a visual field defect in the asymptomatic eye at baseline remained at this level for the 18 months of follow-up. His PERG amplitudes were similar to those of asymptomatic carriers, with 0.78 μV at baseline that did not decline with follow-up.
Conclusions: Declines of the PERG amplitude suggest subclinical retinal ganglion cell dysfunction in asymptomatic G11778A subjects, which is progressive.
Keywords: Leber hereditary optic neuropathy; electrophysiology; mitochondrial DNA.