Myelinated Retinal Nerve Fiber Layer (MRNFL)

Fundus photos demonstrating bilateral (right > left) peripapillary myelinated retinal nerve fiber layer (MRNFL) in a 14-year old boy. Note the typical appearance of MRNFL of a white patch with feathered margins involving the inner retina. In this case, the MRNFL is more prominent in the right eye, and involves juxtapapillary regions superiorly and inferiorly, while in the left eye the MRNFL involves a smaller juxtapapillary region inferiorly. Normally, axons of the retinal ganglion cells are not myelinated anterior to the lamina cribrosa. MRNFL results when there is a defect in the lamina cribrosa allowing oligodendrocytes to gain entry and myelinate the retinal ganglion cell axons within the inner retina. MRNFL is most commonly congenital, though can also result from an acquired optic nerve abnormality. MRNFL is generally benign and does not typically result in vision loss. Reference: Rao R et al. Clinical features, imaging, and natural history of myelinated retinal nerve fiber layer. Reference: Retina. 2019 Jun;39(6):1125-1132