Abstract
Purpose: :
To longitudinally investigate by means of OCT the pattern of fiber loss in the peripapillary Retinal Nerve Fiber Layer (RNFL) of patients with Leber’s Hereditary Optic Neuropathy (LHON).
Methods: :
8 patients (mean age: 18.4±2.9 years) with LHON, as defined by the presence of a pathogenic mtDNA point mutation, were studied during the first two years from the onset of the disease. One randomly selected eye or the second eye affected was considered, respectively, when the disease was simultaneous or not simultaneous. Measurements were carried out at different time points: 2, 6, 12 and 24 months since the disease onset. Stratus OCT was used to analyze peripapillary RNFL thickness (3.4mm diameter). Groups were compared by paired t test followed by box plot graphical distribution.
Results: :
A significant reduction of RNFL was detected in all quadrants between 2 and 6 months and between 6 and 12 months and, at a lesser degree, between 1 and 2 years. In the temporal quadrant most fibers were lost during the first six months of follow–up and no RNFL thinning was detected between one and two years. In the superior and inferior quadrants the RNFL thickness reduction was more evident between 6 and 12 months, but did not stop until the last examination. Notwithstanding a similar pattern of reduction of fiber, patients with recovery of visual acuity (VA) and small central scotoma showed a better preservation of RNFL. During the same follow–up, a high rate of visual recovery (5 eyes out of 7) was observed (mean VA: 0.032 at onset and 0.21 at last examination).
Conclusions: :
OCT allows the longitudinal evaluation of RNFL in LHON. The fiber loss in the temporal quadrant occurs quickly and is almost complete after one year since the disease onset. Conversely, the superior, inferior and nasal quadrant undergo a progressive thinning of the RNFL, which is more evident between 6 and 12 months but can be still detected up to two years. These findings are consistent with the well–known preferential involvement of the papillo–macular bundle and the new notion of a chronic nature of LHON.
Keywords: neuro-ophthalmology: optic nerve • nerve fiber layer