In neonatal mammals, newly grown optic axons are uniformly small in diameter. In the adult, in contrast, axons within the optic nerve can be classified into distinct groups according to their diameter. Because axon diameters are also related to the thickness of the myelin sheath, which in turn determines the velocity of action potential propagation, the question of what determines the axon diam...

In a study involving 50 optic nerves isolated from 3 different strains of adult male mice, C57BL, CBA and (C57BL x CBA) Fl hybrids, and from adult female CBA strain mice, we observed that the mouse had a lower mean total myelinated nerve fibre count than other mammals such as the rat, cat, rabbit, monkey and man where similar information was available from the literature. The nerve fibre spectr...

Optic nerve diseases, such as the glaucomas, lead to changes in the intrapapillary and parapapillary region of the optic nerve head. These changes can be described by the following variables: size and shape of the optic disk; size, shape, and pallor of the neuroretinal rim; size of the optic cup in relation to the area of the disk; configuration and depth of the optic cup; ratios of cup-to-disk...

1) Evaluation of the Optic Nerve requires descriptive quantitative and qualitative intrapapillary and parapapillary regions of the optic nerve head and the retinal nerve fiber layer (RNFL)variables including: a. Size and shape of the optic disc b. Size, shape and pallor of the neuroretinal rim c. Configuration and depth of the optic cup d. Cup-disc diameter ratio and cup-disc area ratio e. Posi...

Raised intracranial pressure (ICP) is associated with poor outcome after brain injury, but is difficult to detect without invasive devices. As a part of the central nervous system, the optic nerve is surrounded by a dural sheath, and the subarachnoid space surrounding the optic nerve is subject to the same pressure changes as the intracranial compartment. Distension of the optic nerve sheath re...

the purpose of this study was to investigate magnetic resonance imaging (mri) of the normal feline eyeand optic nerves using t1-weighted and t2-weighted images. a total of 6 healthy female domestic short haircats age 2-2.5 years and weighing 3.2 ± 0.4 kg were selected. magnetic resonance imaging data werecollected using gemsow (philips) at a magnetic field strength of 1.5 t. dorsal, sagittal, a...

purpose : to report a rare case of large vascularized astrocytoma on optic disc. case report : a 12-year-old boy with history of decreased vision in the left eye since 5-6 months ago was referred to the ocular oncology service at rassoul akram hospital with provisional diagnosis of retinoblastoma. on examination, visual acuity was counting fingers at 50 cm, and a 3+ relative afferent pupillary ...

To the Editor: We applaud Hamilton et al 1 for their recent contribution to the study of the retrobulbar optic nerve sheath diameter as a noninvasive surrogate for intracranial pressure. However, although its science appears sound, this article brings to light what we believe is an important limitation to the study of this topic in general: the lack of uniformity in how exactly the optic nerve ...

Raised intracranial pressure is a complication not just of traumatic brain injury and other acute cerebral insults, but also of a number of general medical conditions. Bedside diagnosis can be difficult; early clinical signs may be misinterpreted, and reliance on cross-sectional imaging studies may further delay diagnosis. Ultrasound is a readily available imaging modality in most critical care...

BACKGROUND To report a rare condition of bilateral optic disc pit in a child. CASE DESCRIPTION A ten-year-old female was admitted with a complaint of headache. Visual acuity was 20/20 in both eyes (OU). Anterior segment examination was normal in OU. Fundus examination revealed optic disc pit (ODP) located temporally with a diameter of 1/5 disc diameter in OU. Intraocular pressure was within n...