Unilateral Extensive Myelinated Retinal Nerve Fiber Layer in a Child

We are reporting a case of an incidental finding of an extensive Myelinated Retinal Nerve Fiber Layers (MRNFL) in a healthy 12-year-old Malay boy. The child did not complain of any blurring of vision until he accidentally closed his seeing eye. On examination, the right visual acuity was 6/6 while the left visual acuity was 6/150. There was no Relative Afferent Pupillary Defect (RAPD). The anterior segment was unremarkable. The fundus of the right eye was normal with a pink optic disc with CDR of 0.4, however, the left eye showed extensive MRNFL involving the whole fundus but sparing the macula. The subjective refraction of the right eye was Plano with 6/6 vision, while the left was –5.50/-1.50x50 with a vision of 6/150. Bjerrum of the right eye was normal but the left eye showed tunnel field at around 20 degrees with 2mm target size. His Humphrey Visual Field (HVF) 30-2, for the right eye, was normal with MD -0.90 while the left eye showed a generalized reduction of the field with MD of -20.23. Optical Coherence Tomography (OCT) of the right eye was normal while the affected eye showed thickening of the RNFL at the peripheral. The other layers of the retina and the foveal region of anatomy were somehow preserved. The axial length of the right eye was 24.10mm while the left eye was 28.06mm. MRNFL is a benign condition. It is commonly seen as a streak of whitish patch starting from the optic disc extending to the retina following the arcuate nerve fiber layer pattern, however, extensive myelinated retinal nerve fiber layer involving the whole retina was not very common and usually associated with amblyopia, axial myopia, and squint. Even though mostly benign and solitary, MNFL can be associated with other systemic condition, therefore, clinicians must rule out other systemic diseases.