Serial Retinal Nerve Fiber Layer Loss Measured with the GDx VCC in a Large Brazilian Pedigree with 11778 mtDNA Leber's Hereditary Optic Neuropathy

Abstract

Abstract: : Purpose: To document progressive loss of retinal nerve fiber layer (RNFL) as measured with the GDx VCC over a twelve month period in both affected subjects and asymptomatic carriers of Leber's Hereditary Optic Neuropathy (LHON) with a 11778 mitochondrial genomic mutation. Methods: In an ongoing study, RNFL thickness was measured with the GDx VCC in October 2002 and in October 2003 in 21 symptomatic LHON subjects and in 71 asymptomatic LHON carriers. The symptomatic subjects had a best corrected visual acuity of less than 20/400, while the carriers maintained a normal VA. All scans with the GDx VCC were performed on the same instrument and by the same examiner. Results: LHON subjects with profound visual loss in October 2002 demonstrated little or no RNFL thinning. Those LHON subjects with less profound visual loss and only moderate RNFL attenuation as of 2002 demonstrated RNFL loss ranging from 9.1 to 19.9 microns of thickness. Seventeen of the 71 (24%) asymptomatic carriers demonstrated mild RNFL thinning ranging from 8.0 to 20.6 microns over the one–year study period. Conclusions: Although classically characterized by acute loss of vision, LHON appears to be a chronic disease characterized by progressive RNFL loss over time in both symptomatic patients with moderate vision loss and in 24% of the asymptomatic carriers with normal visual function. In LHON subjects with profound visual loss and marked RNFL reduction at the initial exam, further loss was essentially unmeasurable with so little RNFL remaining. In subjects with less profound visual reduction, RNFL loss continued to progress years beyond the initial acute symptom of vision loss. In one quarter of the asymptomatic LHON carriers, mild RNFL attenuation was demonstrated over the one–year study period. In this 11778 pedigree, LHON appears to be a chronic disease with an acute phase of symptomatic vision loss, eventually leading to destruction of nearly all of the RNFL.

Keywords: neuro–ophthalmology: optic nerve • nerve fiber layer