RESUMEN
We investigated the relationship between optic nerve (ON) size and visual acuity in children with optic nerve hypoplasia (ONH). The medical records of patients <19 years with ONH who underwent brain magnetic resonance imaging (MRI) and visual acuity assessment were reviewed. ON diameter at orbital and cisternal segments was assessed independently by two neuroradiologists and compared with visual acuity. ON diameter <1.7 mm represented a cutoff, below which was significantly associated with visual acuity of 20/200 or worse (P = 0.04) and above which was significantly associated with visual acuity of 20/40 or better (P = 0.004). ON diameter measured with MRI may provide an early prognostic indication of visual potential for children with ONH.
Asunto(s)
Imagen por Resonancia Magnética , Hipoplasia del Nervio Óptico , Nervio Óptico , Agudeza Visual , Humanos , Imagen por Resonancia Magnética/métodos , Nervio Óptico/diagnóstico por imagen , Nervio Óptico/anomalías , Nervio Óptico/patología , Agudeza Visual/fisiología , Niño , Masculino , Femenino , Hipoplasia del Nervio Óptico/fisiopatología , Hipoplasia del Nervio Óptico/diagnóstico por imagen , Preescolar , Adolescente , Estudios Retrospectivos , Tamaño de los Órganos , LactanteRESUMEN
Septo-optic dysplasia (SOD) is characterized by optic nerve hypoplasia, pituitary gland hypoplasia, and midline abnormalities of the brain. The phenotype of SOD is highly heterogeneous, and the existence of at least two features is considered sufficient for diagnosis. Fovea plana is the absence of a foveal pit in the central fovea, and despite being a developmental abnormality of the fovea, good visual acuity may be retained in some individuals. In this case, a 12-year-old female presented to the ophthalmology clinic with the complaint of blurred vision in her right eye. In dilated fundus examination, optic disc hypoplasia and no foveal light reflex were seen. Magnetic resonance imaging and optical coherence tomography revealed optic nerve, brain midline, and foveal abnormalities. The patient was diagnosed as having SOD with optic nerve hypoplasia and septum pellucidum agenesis, and fovea plana. Both SOD and fovea plana are rare conditions, and there are several reports in the literature that separately describe their clinical features. The most important aspect of this case report is to reveal the unusual co-existence of SOD and fovea plana in a young patient.
Asunto(s)
Fóvea Central/patología , Hipoplasia del Nervio Óptico/complicaciones , Displasia Septo-Óptica/complicaciones , Tabique Pelúcido/anomalías , Niño , Femenino , Fóvea Central/diagnóstico por imagen , Humanos , Imagen por Resonancia Magnética , Hipoplasia del Nervio Óptico/diagnóstico por imagen , Displasia Septo-Óptica/diagnóstico por imagen , Tabique Pelúcido/diagnóstico por imagen , Tabique Pelúcido/patología , Tomografía de Coherencia ÓpticaRESUMEN
In humans, each hemisphere comprises an overlay of two visuotopic maps of the contralateral visual field, one from each eye. Is the capacity of the visual cortex limited to these two maps or are plastic mechanisms available to host more maps? We determined the cortical organization of the visual field maps in a rare individual with chiasma hypoplasia, where visual cortex plasticity is challenged to accommodate three hemifield maps. Using high-resolution fMRI at 7T and diffusion-weighted MRI at 3T, we found three hemiretinal inputs, instead of the normal two, to converge onto the left hemisphere. fMRI-based population receptive field mapping of the left V1-V3 at 3T revealed three superimposed hemifield representations in the left visual cortex, i.e. two representations of opposing visual hemifields from the left eye and one right hemifield representation from the right eye. We conclude that developmental plasticity including the re-wiring of local intra- and cortico-cortical connections is pivotal to support the coexistence and functioning of three hemifield maps within one hemisphere.
Asunto(s)
Imagen por Resonancia Magnética/métodos , Quiasma Óptico/diagnóstico por imagen , Hipoplasia del Nervio Óptico/diagnóstico por imagen , Campos Visuales/fisiología , Vías Visuales/diagnóstico por imagen , Adulto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Quiasma Óptico/fisiología , Hipoplasia del Nervio Óptico/fisiopatología , Estimulación Luminosa/métodos , Corteza Visual/diagnóstico por imagen , Corteza Visual/fisiología , Vías Visuales/fisiologíaRESUMEN
INTRODUCTION: In patients with optic nerve hypoplasia (ONH), the visualisation of the optic disc can be challenging and the definitive diagnosis difficult to ascertain without fundus photography. The use of MRI for diagnosis has been reported as a diagnostic alternative with conflicting results. We retrospectively analysed a disease registry to determine the reliability of orbital MRI measurements of the optic nerve diameter to diagnose ONH, and the correlation with vision outcomes. MATERIALS AND METHODS: From a cohort of 140 patients with ONH (13% unilateral) that had reached age 5 years, we identified 43 subjects who had orbital MRI in addition to fundus photography performed prior to 2 years of age. We compared measurements of the optic nerve diameter from orbital MRI scans to the standard relative optic disc size (disc diameter/disc-macula (DD/DM) distance) by fundus photography. All patients had visual acuity tested at age 5 years. Spearman's correlation coefficient was used to determine the correlation of orbital MRI measurements and fundus photography with the diagnosis of ONH, and with vision outcomes. RESULTS: Relative disc size (DD/DM)<0.35 showed 100% sensitivity and 100% specificity for the diagnostic confirmation of ONH. The optic nerve diameter measurements by orbital MRI displayed a moderate correlation (rs=0.471; p<0.001) with DD/DM and moderate sensitivity for the diagnosis of ONH. Final visual acuity correlated well with DD/DM measurements by fundus photography (rs=-0.869; p<0.001) and moderately with optic nerve diameter by orbital MRI (rs=-0.635; p<0.001). DISCUSSION: Orbital optic nerve diameter from MRI scans has moderate reliability in diagnosing ONH and predicting vision outcomes. Fundus photography for measurements of the optic nerve size should remain the reference for diagnostic confirmation of ONH. These data further support the prognostic value of fundus photography for eventual vision outcomes in this population.