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S. Salvatore, C. Casali, E. Perrotta, G. Morichini, S. Putano, E. M. Vingolo; In vivo Study of Retinal Nerve Fibres Layer in Patients With Autosomal Recessive Spastic Ataxia of Charveloix- Saguenay (ARSACS). Invest. Ophthalmol. Vis. Sci. 2008;49(13):5198.
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To evaluate the clinical features of retinal nerve fibres layer (RNFL) involvement in patients with ARSACS.
3 Italian patients (2 men and 1 woman, aged 21, 38 and 44 years respectively), whose diagnosis was genetically confirmed, underwent complete ophthalmologic evaluation, including optical coherence tomography (OCT) and fundus related perimetry (MP-1 microperimeter).
Visual acuity was 20/20 in all patients. At fundoscopy myelinated retinal nerve fibres, embedding parts of the vessels, were observed in both eyes in two patients; the third patient showed narrowing of the retinal vessels in both eyes, but no myelinated fibres. OCT findings: RNFL thickness analysis showed intense hyperreflectivity in all patients. In those with myelinated fibres it was associated with increased thickness of RNFL in the temporal quadrants in both eyes; Optic Nerve Head (ONH) analysis showed increased optical disc and rim area in eyes with myelinated fibres, and normal results in the third patient; Retinal thickness/volume analysis demonstrated increased thickness in the nasal area of the foveal region symmetrically in all eyes with myelinated fibres, and normal values in the third patient. Fundus related perimetry disclosed reduced retinal sensitivity in the central retina in all patients.
Myelinated retinal nerve fibres are a very rare features of ARSACS patients outside Quebec, where the disorder was first identified. This is the first systematic study of RNFL in this disorder. All patients showed intense hyperreflectivity of RNFL which could be considered as a marker of the disease. Whether increased retinal thickness of RNFL is in fact caused by persistent myelination or, as we suggest, by accumulation of misfolded proteins within the ganglion cell axons caused by sacsin mutation, is still under investigation. Ongoing research targeting the function of the sacsin protein (whose abnormalities are the basis of the disease) and the subsequent changes in neurons. will also help to clarify the pathogenesis of the ophthalmological findings of ARSACS.
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