Myelinated retinal nerve fibres loss in Leber's hereditary optic neuropathy

CLINICAL FEATURES, IMAGING, AND NATURAL HISTORY OF MYELINATED RETINAL NERVE FIBER LAYER

PURPOSE

To evaluate the natural history of myelinated retinal nerve fiber layer (MRNFL) through clinical features and enhanced depth imaging optical coherence tomography.

METHODS

This is a retrospective, noncomparative, case series of patients who underwent thorough clinical examination to document associated ocular and systemic features. Enhanced depth imaging optical coherence tomography was performed when MRNFL was located posteriorly and accessible to imaging.

RESULTS

Seventy-two eyes of 62 patients had a total of 86 MRNFL lesions. Enhanced depth imaging optical coherence tomography (n = 42 eyes) showed that all lesions originated in the nerve fiber layer with preservation of the vascular structures. Mean thickness by enhanced depth imaging optical coherence tomography was 255 μm (median, 182 μm; range, 61-717 μm). Natural history was obtainable in 58 lesions with a mean follow-up duration of 57 months (median, 37 months; range, 2-253 months) with no significant change overall in largest basal diameter (2.5 vs. 2.5 mm; P = 0.361) or thickness (255 vs. 240 μm; P = 0.053). However, evidence of lesion change included growth in base only (≥0.5 mm) (3 of 58; 5%), growth in base (≥0.5 mm) and thickness (≥50 μm) (3 of 58; 5%), and reduction in base (≥0.5 mm) after plaque radiotherapy for choroidal melanoma (3 of 58; 5%).

CONCLUSION

In general, MRNFL is a rare, benign retinal finding with a potential for growth in 10% of cases. This supports previous histopathological reports that MRNFL represents accumulation of both myelin and oligodendrocytes and could be an oligodendrocytic choristoma.

Sectoral loss of myelin and axons in anterior ischemic optic neuropathy

PURPOSE

We report a case of focal myelinated nerve fiber (MNF) loss caused by anterior ischemic optic neuropathy.

CASE REPORT

A 62-year-old woman with segmental MNF presented with anterior ischemic optic neuropathy. One year later, MNF lost superiorly, with preservation of inferior segment MNF. Spectral-domain optical coherence tomography of the optic nerve head and posterior pole retinal thickness showed localized thinning of superior nerve fibers (axons) and retinal thickness.

CONCLUSIONS

This case highlights the focal nature of anterior ischemic optic neuropathy and may be the first patient in whom sectoral loss of myelinated nerve fiber has been photographically documented.

Loss of myelinated retinal nerve fibers from chronic papilledema

An intracranial pilocytic astrocytoma was diagnosed in a 13-year-old boy after he presented with headaches and visual disturbances. The initial ophthalmoscopic examination revealed papilledema bilaterally and myelinated retinal nerve fibers (MRNFs) in the left eye. Serial ophthalmoscopic examinations demonstrated gradual fading of the MRNFs beginning 2 months after tumor resection and their complete disappearance by 2 years after surgery. The disappearance of MRNFs has been described in the presence of ischemia, compression, glaucoma, and demyelinating disease of the optic nerve. This patient demonstrates that loss of myelinated nerves fibers may also occur with the optic atrophy that may follow chronic papilledema.

Syndrome of myelinated retinal nerve fibers, myopia, and amblyopia: a review

Myelinated retinal nerve fibers are developmental anomalies that are present in approximately 1% of all eyes. They may be associated with ipsilateral high myopia and amblyopia, and also may occur in association with various ocular and systemic abnormalities. Lesions may be congenital or acquired, static or dynamic, and can regress in the setting of several described conditions. The pathogenesis is thought to be due to the presence of ectopic oligodendrocyte-like cells in the retina as a result of a development or acquired insult. Visual acuity is typically poor to begin with, and the improvement of visual function in patients undergoing occlusion therapy has been, in general, limited. We discuss a series of 11 patients seen at the Cole Eye Institute with the condition of myelinated retinal nerve fibers, myopia, and amblyopia and describe the clinical characteristics. Three patients also had optic nerve dysplasia and a discussion of the literature related to this association was also performed.