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Neurosurgery Jan 2023Compression of the anterior visual pathways by sellar and parasellar masses can produce irreversible and devastating visual loss. Optical coherence tomography (OCT) is a... (Review)
Review
Compression of the anterior visual pathways by sellar and parasellar masses can produce irreversible and devastating visual loss. Optical coherence tomography (OCT) is a noninvasive high-resolution ocular imaging modality routinely used in ophthalmology clinics for qualitative and quantitative analysis of optic nerve and retinal structures, including the retinal ganglion cells. By demonstrating structural loss of the retinal ganglion cells whose axons form the optic nerve before decussating in the optic chiasm, OCT imaging of the optic nerve and retina provides an excellent tool for detection and monitoring of compressive optic neuropathies and chiasmopathies due to sellar and parasellar masses. Recent studies have highlighted the role of OCT imaging in the diagnosis, follow-up, and prognostication of the visual outcomes in patients with chiasmal compression. OCT parameters of optic nerve and macular scans such as peripapillary retinal nerve fiber layer thickness and macular ganglion cell thickness are correlated with the degree of visual loss; additionally, OCT can detect clinically significant optic nerve and chiasmal compression before visual field loss is revealed on automated perimetry. Preoperative values of OCT optic nerve and macular parameters represent a prognostic tool for postoperative visual outcome. This review provides a qualitative analysis of the current applications of OCT imaging of the retina and optic nerve in patients with anterior visual pathway compression from sellar and parasellar masses. We also review the role of new technologies such as OCT-angiography, which could improve the prognostic ability of OCT to predict postoperative visual function.
Topics: Humans; Tomography, Optical Coherence; Optic Nerve Diseases; Retinal Ganglion Cells; Optic Chiasm; Optic Nerve; Vision Disorders
PubMed: 36519859
DOI: 10.1227/neu.0000000000002186 -
Frontiers in Bioscience : a Journal and... Jan 2008In animals with binocular vision, retinal fibers either project across the midline or they remain on the same side of the ventral diencephalon, forming an X-shaped... (Review)
Review
In animals with binocular vision, retinal fibers either project across the midline or they remain on the same side of the ventral diencephalon, forming an X-shaped commissure known as the optic chiasm. The correct formation of the optic chiasm during development is essential to establish a fully functional visual system. Visual dysfunction associated with axonal misrouting at the optic chiasm has been described in albino individuals and in patients with non-decussating retinal-fugal fiber syndrome. Although little is known about the causes of retinal misrouting in these conditions, the molecular mechanisms responsible for the formation of the optic chiasm are beginning to be elucidated in vertebrates. This review focuses on our current knowledge of how the optic chiasm forms, which will hopefully help us to better understand these congenital anomalies.
Topics: Animals; Axons; Body Patterning; Diencephalon; Drosophila; Gene Expression Regulation, Developmental; Hedgehog Proteins; Homeodomain Proteins; Humans; Mice; Models, Biological; Optic Chiasm; Retina; Signal Transduction
PubMed: 17981656
DOI: 10.2741/2788 -
Diagnostic and Interventional Imaging Oct 2013The exploration of the chiasmal and retrochiasmal visual pathways is based on magnetic resonance imaging. A bitemporal hemianopsis suggests a lesion of the optic chiasm... (Review)
Review
The exploration of the chiasmal and retrochiasmal visual pathways is based on magnetic resonance imaging. A bitemporal hemianopsis suggests a lesion of the optic chiasm while homonymous lateral hemianopsis should lead to a search for a lesion of the retrochiasmal visual pathways. The causes of chiasmal impairment are mainly tumoral. The exploration protocol is based on MRI with T1-weighted sagittal sections, then T2- and T1-weighted coronal sections with and without injection. In case of a retrochiasmal syndrome, the MRI exploration protocol is a function of the type of occurrence of the deficiency and the context.
Topics: Diagnosis, Differential; Dominance, Cerebral; Hemianopsia; Humans; Image Enhancement; Image Interpretation, Computer-Assisted; Imaging, Three-Dimensional; Magnetic Resonance Imaging; Optic Chiasm; Optic Nerve Diseases; Optic Nerve Neoplasms; Visual Field Tests; Visual Fields; Visual Pathways
PubMed: 23891029
DOI: 10.1016/j.diii.2013.06.012 -
Diagnostic and Interventional Imaging Oct 2013Damage to the optic nerve (ON) is characterised by a reduction in visual acuity. Pre-chiasmatic lesions to the optic nerve may be of traumatic, congenital, tumoral... (Review)
Review
Damage to the optic nerve (ON) is characterised by a reduction in visual acuity. Pre-chiasmatic lesions to the optic nerve may be of traumatic, congenital, tumoral (meningioma, glioma), inflammatory or vascular origins. In all cases, MRI is the choice means of exploration, carried out with axial and coronal sections with a thickness of 2.5-3mm and T1 and T2-weighted spin echo sequences. The coronal sections may be carried out with fat signal saturation for an elective study of the size of the retrobulbar portion of the ON.
Topics: Diagnosis, Differential; Guideline Adherence; Humans; Image Enhancement; Image Interpretation, Computer-Assisted; Magnetic Resonance Imaging; Optic Chiasm; Optic Nerve; Optic Nerve Diseases; Optic Nerve Injuries; Optic Nerve Neoplasms; Sensitivity and Specificity; Visual Acuity
PubMed: 23830778
DOI: 10.1016/j.diii.2013.06.001 -
The American Journal of Pathology Jul 1980
Topics: Astrocytoma; Brain Neoplasms; Brain Stem; Cerebellar Neoplasms; Glioblastoma; Humans; Hypothalamus; Neoplasm Staging; Neoplasms, Experimental; Optic Chiasm
PubMed: 6249123
DOI: No ID Found -
NeuroImage. Clinical 2021Vision loss early in life has dramatic consequences on the organization of the visual system and hence on structural plasticity of its remnant components. Most of the...
Vision loss early in life has dramatic consequences on the organization of the visual system and hence on structural plasticity of its remnant components. Most of the studies on the anatomical changes in the brain following visual deprivation have focused on the re-organization of the visual cortex and its afferent and efferent projections. In this study, we performed a quantitative analysis of the volume and size of the optic chiasm, optic nerve, optic tract and the lateral geniculate nucleus (LGN), the retino recipient thalamic nucleus. Analysis was carried out on structural T1-weighted MRIs from 22 congenitally blind (CB), 14 late blind (LB) and 29 age -and sex-matched sighted control (SC) subjects. We manually segmented the optic nerve, optic chiasm and optic tract, while LGN volumes were extracted using in-house software. We also measured voxel intensity of optic nerve, optic chiasm and optic tract. Mean volumes of the optic nerve, optic tract and optic chiasm were reduced by 50 to 60% in both CB and LB participants. No significant differences were found between the congenitally and late-onset blind participants for any of the measures. Our data further revealed reduced white matter voxel intensities in optic nerve, optic chiasm and optic tract in blind compared to sighted participants, suggesting decreased myelin content in the atrophied white matter. The LGN was reduced by 50% and 44% in CB and LB, respectively. In LB, optic nerve volume correlated negatively with the blindness duration index; no such correlation was found for optic chiasm, optic tract and LGN. The observation that despite the absence of visual input about half of the subcortical retinofugal projections are structurally preserved raises the question of their functional role. One possibility is that the surviving fibers play a role in the maintenance of circadian rhythms in the blind through the intrinsically photosensitive melanopsin-containing retinal ganglion cells.
Topics: Blindness; Geniculate Bodies; Humans; Optic Chiasm; Optic Nerve; Visual Cortex; Visual Pathways
PubMed: 34509923
DOI: 10.1016/j.nicl.2021.102809 -
Asian Journal of Surgery Feb 2024
Topics: Humans; Optic Chiasm; Optic Nerve; Foot; Lower Extremity
PubMed: 37945403
DOI: 10.1016/j.asjsur.2023.10.090 -
Scientific Reports Jan 2016Malformations of the optic nerve lead to reduced vision or even blindness. During optic nerve development, retinal ganglion cell (RGC) axons navigate across the retina,...
Malformations of the optic nerve lead to reduced vision or even blindness. During optic nerve development, retinal ganglion cell (RGC) axons navigate across the retina, exit the eye to the optic stalk (OS), and cross the diencephalon midline at the optic chiasm en route to their brain targets. Many signalling molecules have been implicated in guiding various steps of optic nerve pathfinding, however much less is known about transcription factors regulating this process. Here we show that in zebrafish, reduced function of transcription factor Six3 results in optic nerve hypoplasia and a wide repertoire of RGC axon pathfinding errors. These abnormalities are caused by multiple mechanisms, including abnormal eye and OS patterning and morphogenesis, abnormal expression of signalling molecules both in RGCs and in their environment and anatomical deficiency in the diencephalic preoptic area, where the optic chiasm normally forms. Our findings reveal new roles for Six3 in eye development and are consistent with known phenotypes of reduced SIX3 function in humans. Hence, the new zebrafish model for Six3 loss of function furthers our understanding of the mechanisms governing optic nerve development and Six3-mediated eye and forebrain malformations.
Topics: Animals; Eye Abnormalities; Eye Proteins; Gene Expression Regulation, Developmental; Homeodomain Proteins; Nerve Tissue Proteins; Optic Chiasm; Optic Nerve Diseases; Zebrafish; Homeobox Protein SIX3
PubMed: 26822689
DOI: 10.1038/srep20267 -
Pituitary Feb 2021To evaluate whether the occurrence of chiasmal herniation coincides with visual field (VF) deterioration and to compare the course of VF defects in patients with and...
PURPOSE
To evaluate whether the occurrence of chiasmal herniation coincides with visual field (VF) deterioration and to compare the course of VF defects in patients with and without radiological chiasmal herniation following treatment of pituitary adenoma.
METHODS
This retrospective cohort study included 48 pituitary macroadenoma patients with chiasm compression, divided into three groups: Group 1 (N = 12), downward displaced optic chiasm and deteriorated VFs; Group 2 (N = 16), downward displaced optic chiasm; Group 3 (N = 20), control-group matched for tumour size and follow-up VFs, in mean deviation (dB). VFs were compared over time and a severity index, Chiasm Herniation Scale (CHS), for herniation based on radiological parameters was designed.
RESULTS
After treatment, all groups showed improvement of VFs (Gr1: 2.97 dB p = 0.097, Gr2: 4.52 dB p = 0.001 and Gr3: 5.16 dB p = 0.000), followed by long-term gradual deterioration. The course of VFs between patients with and without herniation was not significantly different (p = 0.143), neither was there a difference in the course before and after herniation (p = 0.297). The median time till onset of herniation was 40 months (IQR 6 month-10 years) and did not significantly differ (p = 0.172) between the groups. There was no relation between VFs and the degree of herniation (p = 0.729).
CONCLUSION
Herniation does not appear to have clinical relevance with respect to VF outcome. The newly designed CHS is the first scoring system to quantify the severity of herniation and, in the absence of alternatives, may be useful to describe MRI findings to serve future added value in larger sized outcome studies.
Topics: Adult; Female; Humans; Male; Middle Aged; Optic Chiasm; Pituitary Neoplasms; Retrospective Studies; Visual Fields
PubMed: 33057947
DOI: 10.1007/s11102-020-01088-2 -
Normal measurements of the optic nerve, optic nerve sheath and optic chiasm in the adult population.SA Journal of Radiology 2019Imaging assessment of the anterior visual pathway structures, particularly the optic nerves (ON), requires knowledge of normal dimensions. Several studies suggesting...
BACKGROUND
Imaging assessment of the anterior visual pathway structures, particularly the optic nerves (ON), requires knowledge of normal dimensions. Several studies suggesting techniques and normal ranges have been performed, but most suffer from various methodological flaws. This study is the first to be performed in a South African population.
OBJECTIVES
The aim of this study was to establish normal measurements of the ON, optic nerve sheath (ONS) and optic chiasm (OC) on magnetic resonance imaging (MRI).
METHOD
Eighty normal adults between ages of 12 and 65 years were included in this prospective, quantitative, observational, descriptive study to establish normal measurement of the ON, ONS and OC using a T2W 3D MRI sequence. Measurements (width and height) were undertaken by two observers independently.
RESULTS
A total of 80 participants with a mean age of 35 years were studied: 49 females (61.25%) and 31 males (38.75%). There were no statistical differences in the measurements between gender and age correlation. Interobserver agreement was best for larger structures, that is, OC width and intracranial ON width, respectively. The overall mean of OC width was 13.63 mm (range: 11.13 mm-16.92 mm, standard deviation [s.d.] 1.21); intraorbital ON height at 5 mm behind the globe 2.29 mm (range: 1.63 mm-3.33 mm, s.d. 0.43), and intracranial ON width 4.27 mm (range: 2.46 mm-5.19 mm, s.d. 0.53).
CONCLUSION
Normal measurements of the anterior visual pathway structures on MRI are best reflected in the larger structures. Interobserver variability was poor for the orbital ON, ONS, intracranial ON height and OC height. We recommend that measurements be obtained for the OC width and intracranial ON width. The overall mean for the OC width is 13.63 mm and intracranial ON width 4.27 mm.
PubMed: 31754545
DOI: 10.4102/sajr.v23i1.1772