Purpose: To study retinal nerve fiber layer (RNFL) thickness by optical coherence tomography (OCT) in unaffected carriers with Leber's hereditary optic neuropathy (LHON) mutations.
Design: Cross-sectional study.
Participants: Sixty-six unaffected carriers (44 females and 22 males) were analyzed and compared with an age-matched control group of 70 patients (40 females and 30 males). The statistical analysis was performed after grouping both the patients and the control group on the basis of gender and, for unaffected carriers only, mitochondrial DNA mutation.
Methods: The Fast RNFL Thickness (3.4) scan acquisition protocol was used.
Main outcome measure: Retinal nerve fiber layer thickness as measured by OCT.
Results: With respect to the control group, unaffected male carriers showed a thicker RNFL in the temporal and inferior quadrants and in the 360 degrees average measurement (P = 0.025, P = 0.03, and P = 0.018, respectively). These differences reached statistical significance in subjects carrying the 11778 mutation, whereas only a trend was detected in those with the 3460 mutation. Unaffected female carriers had an increased thickness in the temporal quadrant when compared with the control group (P = 0.003) and no differences in the other measurements. The increase in temporal sectors was statistically significant in females with the 11778 mutation, whereas a trend was detected in those with the 3460 mutation.
Conclusions: A thickening of the temporal fibers was detected in all subgroups of unaffected carriers. This is the first evidence indicating the preferential involvement of the papillomacular bundle in subclinical LHON. This notion previously was based on the early loss of fibers from the temporal quadrant in acute LHON and the selective loss of small-caliber fibers at histopathology. Our study also revealed that males have a more diffuse involvement than females.