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Salvatore S. 1, Iannetti L. 2, Fragiotta S. 1, Vingolo E. M. 1
1 Dipartimento di Scienze Oftalmologiche, Università La Sapienza di Roma, Polo Pontino, Ospedale Alfredo Fiorini e Ospedale Santa Maria Goretti, Latina, Italia;
2 Dipartimento di Scienze Oftalmologiche, Università La Sapienza di Roma, Policlinico Umberto I, Roma, Italia
Aim. The aim of this paper was to determine the anatomical features and compare the differences between time-domain and spectral-domain optical coherence tomography analysis of myelinated retinal nerve fibres (MRNF).
Methods. We enrolled 6 patients with myelinated retinal nerve fibres over a population based, cross-sectional cohort study which included 1436 subjects of 1877 asked to partecipate and examined them by means of optical coherence tomography (OCT) Time- Domain (Stratus OCT, Zeiss) and Spectral- Domain (Spectralis, Heidelberg Tomography).
Results. The MRNF were located most often in the superior temporal region and were bilateral in 17% of cases. In 71% of cases they were associated with macular degeneration. In all cases the optic nerve was surrounded with myelinated fibres. On Time- Domain analysis all patients exhibited normal optic disc and rim area values (2.29 ±0.14 mm2 and 1.97± 0.016 mm2 respectively) and increased reflectivity and thickness of the RNFL (retinal nerve fibres layer) in the area of the myelinated fibres, furthermore this characteristic was accompanied by a posterior cone of shade; on Spectral-Domain RNFL analysis myelin produces the same shadowing but, the increased thickness of RFNL is cancelled by a non signal zone in the site of myelination.
Conclusion. This is the first in vivo ultrastructural study of myelinated retinal nerve fibres. Our results highlight new findings on the their anatomical and ultrastructural appearance and on the possible relationship with macular degeneration. Time and Spectral-Domain OCT are useful to detect ultrastructural changes caused by MRNF, thus better characterizing the anatomical features and pathological association of this developmental anomaly.