Progression of myelinated retinal nerve fibers

Myelinated Retinal Nerve Fiber Progression in a 10-Year Follow-Up. The Beijing Eye Study 2001/2011

PURPOSE

To assess the prevalence of myelinated retinal nerve fibers (MRNFs), the rate of their change in a 10-year follow-up, and associations with ocular and systematic parameters in a population-based cohort.

DESIGN

Longitudinal population-based cohort study.

METHODS

The Beijing Eye study including 4,439 participants aged 40+ years in 2001 and was repeated in 2011, with 2,695 individuals (66.4% of the surviving) being re-examined in 2011. All participants underwent detailed physical and ocular examinations. MRNFs were diagnosed on fundus photographs and their change was assessed using a flicker method of fundus photographs.

RESULTS

Out of 35 eyes (29 participants) with detected MRNFs at baseline (mean prevalence: 0.4% ± 0.26% per eye or 0.7% ± 0.41% per individual), 23 eyes from 20 individuals (17 [85%] participants with unilateral MRNFs) were re-examined in 2011. MRNF enlargement was detected in all 19 eyes (100%) with clear fundus photographs. The mean MRNF area increased from 4,233 ± 3,670 µm² (range: 178-11,643 µm²) at baseline to 5,243 ± 4,092 µm² (range: 196-13,297 µm²) at follow-up (P < .001), by 1,010 ± 1,026 µm² (18-3,967 µm²) or by 47% ± 74% (9%-315%). A larger MRNF increase was associated with an MRNF location distant from the optic disc as compared to a juxtapapillary location (P = .001, standardized regression coefficient beta: -0.53), smaller MRNF area at baseline (P = .006, beta: -0.34), and higher serum concentration of low-density lipoproteins (LDL) (P < .001, beta: 0.57).

CONCLUSIONS

MRNFs (mean prevalence per eye: 0.4%) showed, in association with higher LDL serum concentration and peripheral located MRNF, an enlargement during a 10-year follow-up, while in the same period no new MRNFs were detected in the total study cohort.

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.

Myelinated retinal nerve fibers (MRNF) - Dilemmas related to their influence on visual function

Myelinated nerve fibers (MNF) occur in less than 1% of the population, however, they might be responsible for diagnostic dilemmas in cases with visual loss. The case report of an aged pseudophakic patient with visual deterioration in the right eye and MNF in both eyes is presented. The documentation provided by the patient proved recent several examinations of both fundi, and all of them were described as normal. Physical examination revealed the posterior capsule opacification in the right eye, white lesions on the retina of the right eye around the optic disk, and in the left eye - the peripheral, which could correspond to the myelinated fibers. Although visual field changes and OCTs corresponded to the NMF, it turned out, however, that visual acuity loss was in fact caused by PCO and was reversed by the YAG capsulotomy procedure. This case shows some problems related to MNF diagnosis and evaluation of their influence on visual function.

Syndrome of myelinated retinal nerve fibres, myopia, amblyopia and strabismus in a Nigerian

Myelinated retinal nerve fibres (MRNF) are rare congenital anomalies. They may present in a syndrome characterised by ipsilateral myelinated retinal nerve fibres, myopia and amblyopia. We report a case of this rare condition with unilateral extensive MRNF, axial myopia, amblyopia and strabismus in a Nigerian girl.

Electrophysiological abnormalities associated with extensive myelinated retinal nerve fibers

An observational case report of electrophysiological abnormalities in a patient with anisomyopic amblyopia as a result of unilateral extensive myelinated retinal nerve fibers (MNFs) is illustrated. The electrophysiological readings revealed an abnormal pattern electroretinogram (PERG) but normal full-field electroretinogram readings in the affected eye. The visual-evoked potential was also undetectable in that eye. Our findings suggest that extensive MNFs can be associated with electrophysiological abnormalities, in particular the PERG, which can aid in diagnosing the cause of impaired vision when associated with amblyopia.

Retinal myelinated nerve fibers associated with macular pseudohole

We report the case of a 24-year-old woman who presented unilateral extensive peripapillary myelinated nerve fibers associated with macular pseudohole and bilateral low myopia. Visual acuity, slit lamp biomicroscopy, automated perimetry, fundus color photography, and optical coherence tomography (Stratus OCT) were performed. We discuss the clinical findings and diagnostic details of unilateral extensive peripapillary myelinated nerve fibers associated with macular pseudohole.

[Retinal neovascularization with myelinated nerve fibers]

INTRODUCTION

The prevalence of myelinated retinal nerve fibers is 0.3%-0.6% of eyes. Although they often constitute benign lesions, they are rarely associated with retinal vascular abnormalities including preretinal neovascularization.

CASE REPORT

A 31-year-old patient, with no previous pathological antecedents, consulted us for myodesopsia in her left eye. The exam found a visual acuity of 10/10 and a normal anterior segment in the two eyes. At the ophthalmoscopic examination of the left eye, we noted myelinated nerve fibers in the inferotemporal quadrant that were associated with a temporal neovascular bouquet covering area of 1.5 optic disks. A small amount of intravitreal hemorrhage was found. The ophthalmoscopic examination of the right eye was normal. The treatment consisted in sector-based photocoagulation with argon laser and cryotherapy.

DISCUSSION

The source of neovascularization in the myelinated retinal nerve fibers was discussed. Underlying retinal ischemia is the most probable mechanism. The treatment was based on sector-based or panretinal photocoagulation.

CONCLUSION

Preretinal neovascularization is a rare complication of myelinated nerve fibers. The earlier the care is given, the more complications can be avoided.

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.

Large retinal defect associated with myelinated nerve fibers

We report the unusual association of a large retinal defect with extensive myelinated nerve fibers. The defect was situated in the superior portion of the myelination and choroidal vasculature was visible through it. The defect has remained unchanged during 6 years of follow-up and has not led to any retinal detachment.

Polarimetric nerve fiber analysis in patients with peripapillary myelinated retinal nerve fibers

PURPOSE

The aim of this study was to compare the RNFL thickness in eyes with myelinated retinal nerve fibers (MRNF) and age, sex-matched controls using scanning laser polarimetry.

METHODS

Seventeen patients with MRNF underwent a comprehensive ophthalmological examination including automated visual field testing, and scanning laser polarimetry with Nerve Fiber Analyser (NFA II). Twenty eyes with MRNF from 17 patients were available for the study. Sixteen healthy, age and sex-matched subjects were taken as controls. Retinal nerve fiber thickness measurements of the four sectors (superior, inferior, nasal, temporal) and along the whole circumference of the optic disc were obtained for affected and control eyes, and compared.

RESULTS

Inferior average and inferior integral parameters of the NFA revealed significantly thinner RNFL thickness measurements in eyes with inferiorly located MRNF compared to controls.

CONCLUSION

Retinal myelination alters the birefringent property of the RNFL, and results in diminished thickness measurements. Hence, NFA measurements in patients with MRNF may not be reliable.

Acquired and progressive retinal nerve fiber layer myelination in an adolescent

PURPOSE

To report the onset and progression of retinal nerve fiber layer myelination in an adolescent patient.

METHODS

Case report.

RESULTS

A 7-year-old male was found to have myelination of the retinal nerve fiber layer in the left eye. When he was reexamined at age 14 years, he was found to have new myelination in the right eye, progression of the myelination in the left eye, and bilateral optic nerve drusen.

CONCLUSION

Retinal nerve fiber layer myelination can occur spontaneously in adolescence, progress in adolescence, and be associated with optic nerve drusen.

The effect of myelination on perimetry and retinal nerve fibre analysis

BACKGROUND: Myelinated retinal nerve fibres around the optic nerve head can lead to an enlargement of blind spot with kinetic perimetry. Presumably extensive myelination will also decrease the visual sensitivity with static perimetry. This study reports the effect of myelination on static perimetry in several patients. Scanning laser polarimetry can measure the retinal nerve fibre layer thickness around the optic nerve head in vivo. This technique was applied at the myelination to investigate its effect on retinal nerve fibre layer thickness determination. METHODS: Four eyes of three subjects with myelination around the optic nerve head were tested with Bjerrum screen at one metre to measure the blind spot size. They were followed by Humphrey Visual Field Analyser with a custom pattern to quantify the threshold level at the blind spot region. A GDx Nerve Fiber Analyser was used to measure the retinal nerve fibre layer thickness around the optic nerve head. RESULTS: All the patients demonstrated an enlargement of the blind spot, with different extents, corresponding to the area of myelination. Threshold testing revealed a depression in the myelinated regions. The results for retinal nerve fibre layer were not conclusive with two eyes demonstrating thickening and two eyes showing no effect from myelination. CONCLUSIONS: A static field test with a modern visual field analyser may help to quantify the effect of myelination on visual sensitivity. More studies on the effect of myelination on retinal nerve fibre layer thickness measurement are suggested with more subjects involved.