Leber hereditary optic neuropathy (LHON) is a maternally inherited bilaterally blinding optic neuropathy, predominantly affecting otherwise healthy young individuals, mostly men. The visual prognosis is generally poor, with most patients worsening to at least 20/200 visual acuity. The m.11778G>A (MTND4) mitochondrial DNA mutation is the most common cause of LHON and is associated with poor outcomes and limited potential for meaningful visual recovery. Treatments for LHON are limited, and clinical trials are hampered by inadequate data regarding the natural history of visual loss and recovery. In this article, we review the current literature specifically related to visual function of LHON patients with the m.11778G>A mutation.
Literature review was performed using MEDLINE through PubMed, Cochrane Reviews Library, and Orpha.net with search terms of “Leber hereditary optic neuropathy,” “LHON,” “ND4,” “G11778A,” “visual acuity,” “nadir,” “natural history,” and “registry.” All English-language, peer-reviewed publications with study cohorts of at least 5 LHON patients with the molecularly confirmed m.11778G>A mutation were included.
Meta-analysis of 12 retrospective and 3 prospective studies provided visual function information on 695 LHON patients with the m.11778G>A mutation, 100 (14.4%) of whom were reported to have “recovered” some vision, although definitions of “recovery” varied among studies and idebenone use could not always be excluded. When incorporating age at onset of visual loss into the analyses, and specifically addressing those patients aged 15 years or older, meaningful visual recovery occurred in 23 of 204 (11.3%) patients. A younger age at onset, especially less than 12 years, portends a better visual prognosis and a different natural history of visual loss progression and recovery than in adults.
The classic presentation of LHON patients with the m.11778G>A mutation of severe visual loss with rare or poor recovery from nadir still holds true for most affected individuals. Among patients 15 years and older, recovery of meaningful vision likely occurs in less than 20% of patients, irrespective of how recovery is defined, and ultimate visual acuities of better than 20/200 are rare. Adequate prospective studies with sufficient sample sizes of genotypically homogeneous untreated LHON patients stratified by age, immediately enrolled when symptomatic, followed regularly for adequate periods of time with consistent measures of visual function, and analyzed with a standard definition of visual improvement are unfortunately lacking. Future clinical trials for LHON will require more standardized reporting of the natural history of this disorder.