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Non-Organic Vision Loss
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Ashwini Kini, Mangayarkarasi Thandampallayam Ajjeya, Padmaja Sudhakar
Optic tract lesions: Lesions especially of the optic tract are difficult to pick on clinical testing or even imaging. Sometimes a RAPD and bowtie optic atrophy may be seen on the contralateral side of an optic tract lesion.
Homonymous Hemianopia
Published in K. Gupta, P. Carmichael, A. Zumla, 100 Short Cases for the MRCP, 2020
K. Gupta, P. Carmichael, A. Zumla
The optic nerve contains both the visual and pupillary fibres. The left and right optic nerves join at the optic chiasma and then where the visual fibres cross to join the uncrossed fibres to form the optic tract which travels to the geniculate body. The optic radiation arising from the geniculate body travels to the visual cortex of the occipital lobe.
Describe the retinotopic organisation of the visual pathway. Use an image in the left superior visual field as an example
Published in Nathaniel Knox Cartwright, Petros Carvounis, Short Answer Questions for the MRCOphth Part 1, 2018
Nathaniel Knox Cartwright, Petros Carvounis
In the optic tract: – fibres corresponding to the inferior retina lie laterally– fibres from the upper retina are positioned medially– macular fibres lie posterolaterally.
Assessing lesion location, visual midline perception and proprioception may assist outcome predictions for people affected by lateropulsion
Published in Disability and Rehabilitation, 2023
Unlike the vestibular and proprioceptive systems, inputs from the eyes do not reach the medulla or pons. Instead, visual inputs travel via the optic tract mostly to the lateral geniculate nucleus of the thalamus, and from there to the primary visual cortex in the occipital lobe [9]. From the primary visual cortex, visual inputs undergo multimodal processing in the dorsal (for spatial location) and ventral (for object recognition) streams [9]. Of particular interest is the dorsal stream which terminates in the inferior parietal lobe, the cortical destination of proprioceptive and vestibular inputs. Due to the segregation of the visual system, the inferior parietal lobe is the only cerebral cortex where sensory integration of inputs from all three modalities takes place. In addition, the non-dominant inferior parietal lobe plays a pivotal role in multimodal sensory processing related to spatial location, thus it may be a key cortical region to consider in relation to lateropulsion.
Visual function in guinea pigs: behavior and electrophysiology
Published in Clinical and Experimental Optometry, 2021
Ashutosh Jnawali, Sudan Puri, Laura J Frishman, Lisa A Ostrin
The spatial frequency discrimination determined with optomotor tracking depends, especially in lower vertebrates, on properties of the retinal efferent pathways to subcortical structures.61 The nucleus of the optic tract and the dorsal terminal nucleus of the accessory optical system are involved in the optomotor tracking responses.17,62 The cells in the nucleus of the optic tract and the dorsal terminal nucleus have large receptive fields, thus yielding lower spatial frequency preference.17 Similarly, detection of pattern ERG responses is dependent on several factors, including instrument-specific variables and electrode sensitivity, and retinal cells of origin of the response, not yet established, and therefore, may result in lower spatial frequency discrimination than that predicted solely by retinal ganglion cell density.
Reversible Vision Loss Due to Transependymal Oedema of the Optic Apparatus Secondary to Ventriculoperitoneal Shunt Malfunction
Published in Neuro-Ophthalmology, 2020
Kimberly Nguyen, Claudia M. Prospero Ponce, Aroucha Vickers, Andrew G. Lee
Ventriculoperitoneal shunt (VPS) malfunction may occur secondary to infectious or mechanical etiologies. Shunt infections occur in approximately 11–19.7% of patients1 whereas mechanical complications, including shunt obstruction, fracture, or displacement, occur in up to 45% of patients who require revision.2 The most common symptoms are related to increased intracranial pressure (e.g., headache, nausea, and vomiting or blurred vision from papilloedema). Less commonly, involvement of the optic apparatus, including the optic nerves, optic tracts, optic chiasm, or optic radiations can result in visual field defects and decreased visual acuity (VA).1 We report an unusual case of acute onset vision loss due to transependymal oedema secondary to VPS malfunction that resolved clinically and radiographically after revision of the shunt and remained without recurrence at 6-month follow-up. To the best of our knowledge, this is the first such case in the transependymal oedema involving the visual pathway secondary to VP shunt malfunction in the English language ophthalmic literature.