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P. Barboni, G. Savini, M. Valentino, M. Zanini, F. Fortuna, A. De Negri, F. Sadun, V. Carelli; Retinal Nerve Fiber Layer Thickness in Patients Showing Visual Recovery in Leber’s Hereditary Optic Neuropathy . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1201.
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Purpose: To measure by OCT the retinal nerve fiber layer (RNFL) thickness in patients with Leber’s Hereditary Optic Neuropathy (LHON) and recovery of visual acuity. Methods: 23 patients (mean age: 36.5±14.5 years) with LHON, as defined by the presence of a pathogenic mtDNA point mutation, were compared to an age and optic nerve head (ONH) size–matched control group of 23 individuals. StratusOCT was used to detect the peripapillary RNFL thickness (RNFL thickness 3.4 acquisition protocol) and measure ONH size (Fast optic disc acquisition protocol). Computerized perimetry was performed to assess the visual field. The eye with the best visual acuity was selected in the patient group and compared to one randomly selected eye of subjects in the control group. Patients were further classified into three categories, according to the size of the central scotoma: type 1 showing a scotoma > than 20° and a prevalent pattern of fenestration; type 2 showing a scotoma of 10–20° and a prevalent pattern of restriction; type 3 showing a scotoma <10° and an exclusive pattern of restriction. Results: With respect to the control group, patients with LHON and recovery of visual acuity revealed a reduced RNFL thickness (p <0.0001) in the 360° average and in each quadrant measurement. According to analysis of variance and multiple comparisons post tests, RNFL values of all quadrants, except the temporal, were significantly higher in the case of a scotoma smaller than 10° (type 3). After grouping the three categories, the 360° RNFL measurement was positively correlated to visual field mean deviation (r = 0.6984, p = 0.0018) and, to a lesser extent, to visual acuity (r = 0.4736, p = 0.0224). Conclusions: LHON patients with recovery of visual acuity show a stronger association of RNFL thickness with visual field preservation than with final visual acuity. The type 1 patients feature a patchy gain of function of few bundles of fibers on a generalized loss. At variance, type 3 patients have a wider preservation of fibers with a better visual outcome. Type 2 patients show a mixed pattern and an intermediate visual outcome. We conclude that recovery of visual function may have different phyhsiopathological substrates, ranging from preservation of myelinated axons from death to re–gain of function in survived axons, possibly through re–myelination.
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