Visual-Evoked Potential in Neuro-Ophthalmology
Vivek Lal in A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
The optic nerves form connection between retina and the brain. Light impulses stimulate the photoreceptors (rods and cones) which further synapse with the inner nuclear or bipolar layers; bipolar cells synapse further with the ganglion cell layer. The axons of the ganglion cell form the optic nerve. The two optic nerves joined at optic chiasma. The optic tract starts from the optic chiasma and terminates in the lateral geniculate body. The optic tract contains ipsilateral temporal and contralateral nasal retinal fibers. The fibers carrying impulses from upper part of retina terminate in the ventromedial segment and those from lower part terminate in the ventrolateral segment of geniculate body. The ipsilateral temporal and contralateral nasal retinal fibers terminate alternatively in six layers in lateral geniculate body. Lateral geniculate body neurons form optic radiation, which pass posteriorly to terminate in the striate cortex (area 17). The macular fibers occupy the larger portion of occipital lobe at the occipital pole in a wedge-shaped area. The upper half and lower half of the retinal fibers relay superior and inferior to the calcarine fissure, respectively (Figure 3B.1).
Head, neck and vertebral column
David Heylings, Stephen Carmichael, Samuel Leinster, Janak Saada, Bari M. Logan, Ralph T. Hutchings in McMinn’s Concise Human Anatomy, 2017
The eye (eyeball), the organ of vision, is almost a complete sphere, about 25 mm (1 inch) in diameter, lodged in the anterior half of the orbit (orbital cavity) of the skull and protected by the eyelids. Three layers make up the wall of the eye: the sclera, the choroid and the retina (from outside inwards); the retina contains the light receptors. However, anteriorly the sclera is replaced by, and is continuous with, the transparent cornea, which admits light into the eye. The optic nerve resides in the posterior half of the orbit, with most of the extraocular muscles that move the eye and other nerves and vessels all embedded in the orbital fat (Fig 3.29B). The lacrimal apparatus starts with the lacrimal gland lying superiorly and laterally in the orbit, which secretes tears over the front of the eye, and is completed by the duct systems lying medially that dispose of these tears into the nose via the nasolacrimal duct.
Introduction
John W. Scadding, Nicholas A. Losseff in Clinical Neurology, 2011
Disturbances of vision are common neurological problems. Loss of visual acuity points to damage to the eye itself, or to the optic nerve. Lesions behind the optic chiasm produce loss of vision in the opposite half of the visual field (hemianopia), but leave intact at least the ipsilateral half of central macular vision, and this is sufficient to provide a normal visual acuity (Figure 1.1). Patients with hemianopias complain of difficulty reading, or of bumping into objects in the blind half-field. Double vision (diplopia) occurs when the axes of the two eyes are out of alignment. This happens when one eyeball is displaced by some mass in the orbit, or if the ocular muscles are weak because of either primary muscle disease or damage to external ocular nerves (Figure 1.2).
Localized co-delivery of CNTF and FK506 using a thermosensitive hydrogel for retina ganglion cells protection after traumatic optic nerve injury
Published in Drug Delivery, 2020
Dongmei Wang, Mengmeng Luo, Baoshan Huang, Wa Gao, Yan Jiang, Qing Li, Kaihui Nan, Sen Lin
The focal of traumatic optic nerve injury is usually located at the back of the eyeball, making the treatment even more challenging for localized drug delivery owing to the anatomical limitation. Therefore, we have developed a strategy to deliver therapeutic agents directly to the back of eyeball through the nose under guidance of trans-nasal endoscope in big experimental animals (unpublished data). Apparently, it is warranted to screen constituents and drugs in small experimental animals to achieve the desirable bio-effect in vivo. However, the channel in small animals (rabbits) from the nose to the back of the eyeball is too narrow to perform the trans-nasal endoscope procedure. Therefore, in this study, we exposed the optic nerve of rabbits through surgical procedure and directly smeared the drug-loaded hydrogel on the focal to evaluate the bio-effects of this material with the less challenging approach. Based on these findings on rabbits, we look forward to reproducing it on large animals for improved localized delivery of therapeutic molecules using a less invasive approach with the help of a trans-nasal endoscope.
Time-Frequency Analysis of Photopic Negative Response in CRVO Patients
Published in Seminars in Ophthalmology, 2020
Soroor Behbahani, Alireza Ramezani, Mohammad Karimi Moridani, Hamideh Sabbaghi
In the eyes with CRVO, most damages occur in the inner retina.23,24 The i-wave component, which is a post-b‐wave component of the photopic ERG, is claimed to derive from the adjacent RGC layer or more distally.25,26 Moreover, it has been shown that the PhNR, which is a negative wave that appears after the b-wave, has significantly decreased compared with other measured parameters in the CRVO. Since PhNR reflects the internal function of the retina, it could be an ideal parameter for evaluating the function of the retina in the eyes of the CRVO.27–29 It can also be an approach for the assessment of the optic nerve function in the retina.30 In this study, we tried to evaluate the frequency characteristics of i-wave and PhNR in eyes with CRVO using the CWT method.
Neuroprotective effects of inhibitors of Acid-Sensing ion channels (ASICs) in optic nerve crush model in rodents
Published in Current Eye Research, 2018
Dorota L. Stankowska, Brett H. Mueller, Hidehiro Oku, Tsunehiko Ikeda, Adnan Dibas
Ocular trauma is a major cause of monocular blindness and visual impairment throughout the world where at least half a million people getting it annually.1,2 Ocular trauma can occur in almost any setting (sport-related activities, work place, traffic accident, and physical assault). An estimated 2.4 million annual eye injuries with over than a billion dollars in costs have been reported in the USA (American Academy of Ophthalmology). Although ocular injuries are predominantly in males (95%), unfortunately they are easily preventable (American Academy of Ophthalmology). Among all ocular tissues, the optic nerve is especially vulnerable to indirect and direct trauma-causing functional impairment of vision. Unfortunately, the diagnosis of optic nerve injury may be delayed due to other life-threatening injuries. The examination of optic nerve trauma requires clinical evaluation and such examination of severely injured patients is a major challenge for ophthalmologists.2 There are no current medications to rescue the optic nerve. Therefore, there is an urgent need to develop neuroprotective drugs for traumatic optic nerve injuries.
Related Knowledge Centers
- Glia
- Neuroanatomy
- Optic Disc
- Retina
- Visual System
- Brain
- Cranial Nerves
- Optic Stalk
- Retinal Ganglion Cell
- Optic Chiasm