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At least 127 records · Page 7Linked to original sources
PubMed1999

Direct connections between dendritic terminals of tectal ganglion cells and glutamate-positive terminals of presumed optic fibres in layers 4-5 of the optic tectum of Gallus domesticus. A light- and electron microscopic study.

The principal afferent fibres of the avian optic tectum are the optic fibres of retinal origin. They terminate on the contralateral side, in the external layers (2-7) of the optic tectum (called optic layers) turning into these layers from the external surface. The terminal branchings of the optic fibres develop four densely innervated areas in layers 2, 3, 4-5 and 7. Their terminals are large and of various appearance in the different areas. In the middle third of the optic layer (in layers 4-5), thin dendritic terminal sections of tectal ganglion cells (according to Ramòn y Cajal) of layer 13 terminate into bunches. Phaseolus vulgaris lectin immunotracer corroborates these dendritic endings (further: dendritic terminals) of tectal ganglion cells. The direct connections between these dendritic terminals and the supposed optic fibres were studied under electron microscope and it was found that the large terminals of optic fibres containing round synaptic vesicles establish asymmetrical synapses with several dendritic profiles, among them Phaseolus lectin labelled dendritic terminals of ganglion cells. This result morphologically supports the former physiological observation of a direct synaptic transmission between optic fibres and ganglion cells of layer 13. In addition, on the dendritic terminals of ganglion cells, symmetrical synapses established by GABA-positive terminals were found. The optic terminals, the GABA-immunopositive terminals and the dendritic terminals of ganglion cells form complex synaptic units surrounded with glial sheath, and thus they establish glomerulus-like synaptic units. The size of the dendritic tree and the branching pattern of the dendrites of ganglion cells point to divergence and convergence in visual transmission.

Animals↗
PubMed1982

Quantitative study of optic nerve head capillaries in experimental optic disk pallor.

We obtained quantitative measurements of capillary numbers, areas, and diameters in atrophic (pale) and normal primate optic nerve heads. The number of capillaries per square millimeter in pale optic disks was not significantly different from that in normal optic disks. Because the loss of all nerve fibers leads to a 50% decrease in nerve head substance, capillaries must atrophy to maintain a constant relationship between capillary number and tissue volume. The mean size of individual capillaries in atrophic nerve heads was smaller than normal, leading to a decrease of more than 27% in the percentage of tissue volume occupied by capillaries. When this decrease in capillary volume was mimicked in the normal optic disk by reducing the hematocrit value, optic disk pallor did not result. Hence, the development of optic disk pallor appears to be the result of thinning of the neural tissue of the rim of the optic disk and the consequent change in tissue composition and optical transparency, rather than of a loss of optic disk capillaries.

Animals↗
PubMed2005

Isolated optic nerve lymphoma diagnosed by optic nerve biopsy.

PURPOSE: To report a case of isolated optic nerve lymphoma diagnosed by optic nerve biopsy. DESIGN: Case report. METHODS: A 66-year-old woman was referred to the Neuro-Ophthalmology Service because of a decrease in visual acuity and right optic disk edema. RESULTS: A magnetic resonance image of the brain showed only enhancement of the optic nerve. An examination that included ANA, c-ANCA, p-ANCA, Lyme titers, FTA-ABS, ACE level, chest x-ray, and lumbar puncture was negative. Because of rapid progression on clinical examination and serial imaging, an optic nerve biopsy was performed, which showed B-cell lymphoma. CONCLUSION: Optic nerve lymphoma can be confused with a variety of inflammatory and neoplastic infiltrations of the optic nerve on clinical and radiographic examinations. Optic nerve biopsy can be valuable in diagnosing isolated optic nerve lymphoma if other diagnostic tests are unrevealing, but the procedure carries considerable risk of loss of visual acuity and should be recommended judiciously.

Aged↗
PubMed2002

Optic nerve arteriovenous malformation causing optic apoplexy: case report.

OBJECTIVE AND IMPORTANCE: Vascular malformations in the optic pathway are rare. Only one case of pathologically confirmed arteriovenous malformation (AVM) of the optic nerve has been reported previously. We document the case of a patient with an optic nerve AVM who presented with optic apoplexy that was diagnosed with the use of magnetic resonance imaging. CLINICAL PRESENTATION: A 15-year-old girl developed left visual disturbance of sudden onset while playing badminton. A magnetic resonance imaging scan disclosed left optic nerve swelling and intraoptical hemorrhage, although an angiogram did not reveal abnormal vessels. INTERVENTION: The patient underwent total removal of the hematoma and tangles of the abnormal vessels in the left optic nerve, which was diagnosed pathologically as an AVM. The patient recovered visual acuity, but the left visual field defect remained unchanged. CONCLUSION: Along with cavernous malformations and optic gliomas, AVMs can be a rare cause of optic nerve apoplexy. T2-weighted magnetic resonance imaging is useful in rendering the diagnosis of an optic nerve AVM, observed as a mass lesion consisting of serpiginous, tangled, low-intensity bands. Early surgical treatment is recommended to obtain a rapid recovery.

Adolescent↗
PubMed2004

Optic nerve enhancement in hypotensive ischemic optic neuropathy.

A 57-year-old woman who had hypotension and cardiac arrest during coronary artery bypass grafting developed hypotensive ischemic optic neuropathy with no light perception vision OU. Bilateral mid-orbital optic nerve enhancement was found on magnetic resonance imaging (MRI) eight weeks after surgery. Re-examination 16 weeks after surgery showed no light perception vision, dilated un-reactive pupils, and pale optic discs. Bilateral optic nerve enhancement persisted on MRI. Optic nerve enhancement has been reported commonly in radiation-induced ischemic optic neuropathy, occasionally in arteritic ischemic optic neuropathy, and rarely in nonarteritic ischemic optic neuropathy. It has never been reported in hypotensive ischemic optic neuropathy.

Blindness↗
PubMed2006

Optical coherence tomography of the optic nerve head: interindividual reproducibility.

PURPOSE: Optical coherence tomography may be a new technique for quantitative 3-dimensional assessment of the optic nerve head for diagnosis of optic nerve anomalies and diseases such as the glaucomas. The purpose of the present study was to examine its reproducibility. PATIENTS AND METHODS: The clinical noninterventional study included 10 randomly chosen eyes of 10 healthy individuals who underwent 24 optical coherence tomographic examinations with the high-resolution and fast scan program, interactively corrected or uncorrected. The pupils were not dilated. All examinations were performed by 3 examiners independently of one another. The coefficient of variation was calculated as the ratio of the mean of the standard deviations divided by the mean of the means. RESULTS: The coefficients of variation for redetermination of optic disc area, ranging between 0.047 and 0.119, were lowest for the manually corrected fast scan mode and highest for the uncorrected fast scan mode. For remeasurements of the neuroretinal rim area, the best mean coefficient of variation was 0.073+/-0.026 (corrected fast scan mode). CONCLUSIONS: In healthy eyes, the morphometric measurements of the optic nerve head by optical coherence tomography show a relatively high reproducibility with mean coefficients of variation lower than 10% for remeasurements of the optic disc and neuroretinal rim area. With undilated pupils, reproducibility is better with the fast scan mode with interactive correction of the outlining of the optic disc border than it is with the high-resolution mode.

Adult↗
PubMed2007

Decreased retinal nerve fibre layer thickness detected by optical coherence tomography in patients with ethambutol-induced optic neuropathy.

BACKGROUND: It is difficult to assess the degree of optic nerve damage in patients with ethambutol-induced optic neuropathy, especially just after the onset of visual loss, when the optic disc typically looks normal. AIM: To evaluate changes in retinal nerve fibre layer thickness (RNFLT) using optical coherence tomography (OCT) in patients with optic neuropathy within 3 months of cessation of ethambutol treatment. DESIGN: A retrospective observational case series from a single neuro-ophthalmology practice. METHODS: 8 patients with a history of ethambutol-induced optic neuropathy were examined within 3 months after stopping ethambutol treatment. All patients underwent a neuro-ophthalmologic examination, including visual acuity, colour vision, visual fields and funduscopy. OCT was performed on both eyes of each patient using the retinal nerve fibre layer analysis protocol. RESULTS: The interval between cessation of ethambutol treatment and the initial visit ranged from 1 week to 3 months. All patients had visual deficits characteristic of ethambutol-induced optic neuropathy at their initial visit, and the follow-up examination was performed within 12 months. Compared with the initial RNFLT, there was a statistically significant decrease in the mean RNFLT of the temporal, superior and nasal quadrants (p = 0.009, 0.019 and 0.025, respectively), with the greatest decrease in the temporal quadrant (mean decrease 26.5 mum). CONCLUSIONS: A decrease in RNFLT is observed in all quadrants in patients with ethambutol-induced optic neuropathy who have recently discontinued the medication. This decrease is most pronounced in the temporal quadrant of the optic disc.

Aged↗
PubMed1995

Optic disc size and optic nerve damage in normal pressure glaucoma.

BACKGROUND: Recent reports indicate that eyes with normal pressure glaucoma have larger optic discs than eyes with primary open angle glaucoma or normal eyes. This study was performed to find whether, in normal pressure glaucoma, a large disc is associated with more optic nerve damage than a small disc. METHODS: Colour optic disc photographs of 74 patients with normal pressure glaucoma were assessed morphometrically. RESULTS: Taking the study group as a whole, the optic disc size decreased significantly (p = 0.04) with increasing visual field defect. In an intraindividual bilateral comparison, the side differences in the disc area of the right minus the left eye of the same individual were not significantly correlated with the side differences in the mean visual field defect. CONCLUSIONS: The results indicate that the eye with the larger optic disc, when compared with the contralateral eye with the smaller optic nerve head, showed neither a significantly more marked nor less pronounced glaucomatous optic nerve damage. It suggests that for a given patient the degree of glaucomatous optic nerve atrophy was not markedly associated with the optic disc size. The finding that patients with large visual field defects had smaller discs than patients with moderate perimetric loss may indicate that the results of previous cross sectional studies reporting on an unusually large disc size in normal pressure glaucoma may be due partially to selection.

Female↗
PubMed1999

The effects of high-dose corticosteroid therapy on optic nerve head blood flow in experimental traumatic optic neuropathy.

PURPOSE: The objective of this study was to ascertain the effect of high-dose steroid therapy in traumatic optic neuropathy using the Heidelberg retina flowmeter (HRF) to detect changes in optic nerve head blood flow. METHODS: We experimentally damaged the optic nerves of 10 white rabbits with a Hartman mosquito clamp. The first group (n = 5) was treated with intravenous dexamethasone (0.25 mg/kg) every 6 h for a 48-hour period. The second group (n = 5) served as controls. Both groups were tested prior to operation, 1 week, 1 month and 2 months after surgery. RESULTS: Experimental optic nerve damage caused a significant decrease in optic nerve head blood flow of 50.51% (p = 0.001), with a volume decrease of 46.02% (p = 0.001) and a velocity reduction of 43.12% (p = 0.002) compared to the baseline. After 2 months, in the group treated with high-dose corticosteroid therapy, optic nerve head blood flow was increased by 76.90% (p = 0.012), volume by 77.53% (p = 0.012) and velocity by 47. 21% (p = 0.012) compared to the control group. CONCLUSION: The high-dose corticosteroid therapy improved the optic nerve head blood flow as demonstrated in experimental traumatic optic neuropathy. The HRF may be used to assess the therapeutic responses in traumatic optic neuropathy under variable conditions.

Animals↗
PubMed2000

Leber's hereditary optic neuropathy differentially affects smaller axons in the optic nerve.

PURPOSE: Leber's hereditary optic neuropathy (LHON), though known to be due to 1 of 3 pathogenic mtDNA point mutations (nucleotide positions 11,778, 3460, and 14,484), usually manifests itself acutely in young adulthood with a stereotypical presentation of dyschromatopsia, loss of central vision, and loss of the papillomacular bundle nerve fiber layer. Histopathologic investigations have demonstrated devastating losses of axons with relative sparing of the most peripherally placed fibers in the optic nerves. This study was designed to morphometrically investigate the nerve fiber spectrum from ultrastructural studies of optic nerves obtained from 2 patients with LHON. METHODS: Two cases of LHON were molecularly characterized and the optic nerves from these cases studied by light microscopy and electron microscopy. Montages were made of electron micrographs cut orthogonal to fibers obtained from the periphery of each optic nerve, and these were then used for the measurement of each axon (short and long axis) and its myelin sheath. From this, a spectrum of nerve fiber layer was generated, yielding axon caliber profiles that could be compared between optic nerves. RESULTS: The total depletion of optic nerve fiber population in the 2 cases of LHON varied from 95% to 99%. Those fibers that were spared were limited to the peripheral optic nerve. The nerve fiber layer spectra of these remaining fibers showed a marked diminution of the first peak of axons of less than 1 micron in diameter, with relative emphasis of a second peak of axons of about 2 microns in diameter. In comparison to normal controls, this reflected a preferential loss of the smallest axons corresponding to the P-cell population. CONCLUSIONS: The clinical features of dyschromatopsia and central scotoma (with preservation of pupils) in LHON suggests the selective loss of the P-cell population known to subserve these (and not pupil) functions. This also correlates well with the fundus findings of early losses of the papillomacular bundle. The present study extends these findings to demonstrate a relative preservation of the M-cells in the optic nerve as reflected by the nerve fiber spectral profile. This selective loss of smaller fibers and their corresponding smaller retinal ganglion cells may, in addition to explaining the clinical features in LHON, provide valuable insights as to the exact pathophysiologic mechanisms by which mitochondrial impairment may induce apoptosis in vulnerable neurons.

Adult↗
PubMed2004

Optical coherence tomography analysis of axonal loss in band atrophy of the optic nerve.

AIMS: To measure axonal loss in patients with band atrophy of the optic nerve caused by optic chiasm compression using optical coherence tomography and to evaluate its ability in identifying this pattern of retinal nerve fibre layer (RNFL) loss. METHODS: Twenty eyes from 16 consecutive patients with band atrophy of the optic nerve and permanent temporal hemianopia due to chiasmal compression, and 20 eyes from an age and sex matched control group of 16 healthy individuals, were studied prospectively. All patients were submitted to an ophthalmic examination including perimetry and evaluation of the RNFL using optical coherence tomography. Mean RNFL thickness around the optic disc was compared between the two groups. RESULTS: The mean (SD) peripapillary RNFL thickness of eyes with band atrophy was 101.00 (9.89) microm, 62.21 (12.71) microm, 104.89 (12.60) microm, and 50.13 (16.88) microm in the superior, temporal, inferior, and nasal regions, respectively. The total RNFL mean was 79.94 (7.17) microm. In the control group, the corresponding values were 140.10 (16.06) microm, 86.50 (12.17) microm, 144.60 (15.70) microm, and 97.94 (16.02) microm. The total RNFL mean was 117.72 (9.53) microm. The measurements were significantly different between the two groups. Measurements in each of twelve 30 degrees divisions provided by the equipment also showed significantly different values between eyes with band atrophy and normal controls. CONCLUSIONS: Optical coherence tomography was able to identify axonal loss in all four quadrants as well as in each of the twelve 30 degrees segments of the disc. Thus, it seems to be a promising instrument in the diagnosis and follow up of neuro-ophthalmic conditions responsible for RNFL loss, even if predominantly in the nasal and temporal areas of the optic disc.

Adult↗
PubMed1981

Regional differences in pigeon optic tract, chiasm, and retino-receptive layers of optic tectum.

Electron-microscopic examination of the pigeon optic chiasm, tract, stratum opticum, and retino-receptive layers of the optic tectum revealed regional differences at each level. Axonal size in the fiber pathways paralleled that previously reported for pigeon optic nerve, with mean diameter values of 0.96 micrometer for optic chiasm and 1.06 micrometer for optic tract. The dorsolateral aspects of these pathways contained a heterogeneous population of fibers (mean diameter congruent to 1.44 micrometer) similar to that found in the nasal portion of optic nerve, while the ventromedial regions were occupied by a more homogeneous population of smaller fibers (mean diameter congruent to 0.82 micrometer) resembling those observed in the temporal portion of the nerve. The retino-receptive layers of anteroventral optic tectum (avT) differed ultrastructurally from those of posterodorsal tectum (pdT) with respect to the thickness of horizontal dendrites in layer 2-3, the size of optic terminals in layers 2-7, and the number of synaptic contacts per terminal. These findings point towards a regional variation in the processing of visual information throughout the retino-tectal system and suggest that neurons in avT vs. pdT should show differences in the way they modify the neurophysiological characteristics of their respective optic inputs.

Animals↗
PubMed1990

Fibre organization of the monkey's optic tract: I. Segregation of functionally distinct optic axons.

The fibre organization of the monkey's optic tract was examined by implanting pellets of horseradish peroxidase into different locations within the tract, or into the superior colliculus and pretectum. Retinae were examined for the distribution, size, and morphological types of retrogradely labelled ganglion cells; optic tracts were examined for the distribution of anterogradely and retrogradely labelled axonal profiles; and lateral geniculate nuclei were examined for the distribution of anterogradely labelled processes within distinct geniculate laminae. Localized implants in the optic tract produced retrograde labelling of ganglion cells across wide regions of the retinal surface. The maximum density of labelled cells was always substantially less than the total ganglion cell density known to be present at those retinal loci. Distinct retinal ganglion cell types were labelled from differing regions within the optic tract: implants into the deep (dorsal) portion of the tract, far removed from the outer, pial, surface, retrogradely labelled predominantly P beta retinal ganglion cells, whereas implants into the superficial (ventral), subpial, part of the tract retrogradely labelled primarily the other retinal ganglion cell types, i.e., the P alpha, P gamma, and P epsilon cells. Within any given class of axon, there is a mapping of the centroperipheral retinal axis across the deep-to-superficial dimension of the tract, but this retinotopy is extremely coarse. Anterograde labelling of axonal terminations within the lateral geniculate nucleus showed a corresponding specificity for distinct geniculate laminae, the deep implants labelling the parvocellular laminae, superficial implants labelling the magnocellular laminae. Implants into the visual centres of the midbrain produced retrograde axonal labelling rostral to the lateral geniculate nucleus only in the superficial part of the optic tract. These results demonstrate that the monkey's optic tract is not a simple topographic mapping of retinal eccentricity. Rather, the primary organizational principle is that of a segregation of functionally distinct optic axon classes. As fibre order in the mammalian optic tract is also a chronological index of axonal arrival during development, the present results provide specific predictions about the temporal order of ganglion call genesis and axonal addition within the visual pathway. They also provide an anatomical basis for the functionally selective visual impairments that may arise following local damage to the optic tract in humans.

Animals↗
PubMed1987

Optic nerve head drusen associated with abnormally small optic discs.

Using Littmann's method for correcting the magnification of central fundus photographs we evaluated the absolute optic disc size in 26 eyes with visible optic nerve head drusen. The optic nerve head area in these eyes (1.79 + -0.50 mm2) was significantly smaller (p less than 0.001) than normal standard values previously determined (2.89 + -0.76 mm2). The drusen were most commonly located and most densely packed at the upper and lower optic disc border. The coefficients of variation of the method's reproducibility were 0.06 for intraobserver and 0.11 for interobserver determination. The abnormally small optic disc indicating an abnormally small optic nerve scleral canal may inhibit by mechanical compression the axonal flow within the optic nerve fibers. This may ultimately lead to drusen formation. Pseudoneuritis also associated with an abnormally small optic disc may be a preceder of acquired optic nerve head drusen.

Adolescent↗
PubMed2006

Resolution of optic nerve edema and improved visual function after optic nerve sheath fenestration in a patient with osteopetrosis.

PURPOSE: To describe the outcome of a patient with visual loss and optic nerve edema that resulted from osteopetrosis who underwent an optic nerve sheath fenestration (ONSF). DESIGN: Interventional case report. METHODS: A 33-year-old man with osteopetrosis had bilateral visual field loss and optic nerve edema. Computed tomography and magnetic resonance imaging demonstrated open optic canals. Although a lumbar puncture showed a normal opening pressure, there were other findings that were suggestive of increased intracranial pressure. The patient elected to undergo a unilateral optic nerve sheath fenestration. RESULTS: After ONSF, the patient experienced markedly improved visual acuity, visual field, and optic nerve appearance. CONCLUSION: Individuals with visual loss and optic disk edema that is associated with osteopetrosis may benefit from ONSF if the optic canals appear to be open and the optic nerve edema is thought to be related to increased intracranial pressure.

Adult↗
PubMed2006

Integrated-optic biosensor by electro-optically modulated surface plasmon resonance.

We present a new integrated-optic surface plasmon resonance (SPR) biosensor based on electro-optical modulation. The SPR characteristics for the analyte concentration detection can be electro-optically modulated by applying the voltage on the electrodes of the biosensor fabricated on lithium niobate, which is an excellent electro-optic material. Two measurement methods, electro-optically modulated SPR spectral measurement and electro-optically modulated SPR intensity measurement, are demonstrated and their measurands are the SPR wavelength and the output optical intensity, respectively. Human serum albumin is coated on the gold film surface of the proposed biosensor to detect the concentration of beta-blocker, which is a remedy for heart disease. As the applied voltage increases such that the effective index of guided mode rises, the SPR wavelength shifts toward the long wavelength side and the output optical intensity at the wavelength of 632.8 nm diminishes. The linear regression slope of the relation between the measurand and the applied voltage is dependent on the analyte concentration and can be used to determine the concentration variation. Experimental results measured by the electro-optically modulated SPR methods are compared with those measured by the conventional spectral and intensity methods, and the effects of waveguide width on the biosensor performance are discussed.

Electrodes↗
PubMed1999

Experimental optic cup enlargement caused by endothelin-1-induced chronic optic nerve head ischemia.

PURPOSE: Vascular insufficiency of the optic nerve head may contribute to glaucomatous optic neuropathy, especially in normal-tension glaucoma. We investigated the effect of chronic optic nerve head ischemia, created by repeated intravitreal injection of endothelin-1 (ET-1), on the morphology and function of the optic nerve. METHODS: In pigmented rabbits, we injected ET-1 (10(-6) M, 10 microL) into the posterior vitreous of one eye twice a week for 4 weeks (N = 7). The vehicle for ET-1 was injected into the contralateral eye as a control (N = 7). The subsequent observation period was set at 8 weeks. The microcirculation of the optic nerve head was noninvasively monitored with a laser speckle circulation analyzer. To evaluate the changes of visual function, visual-evoked potentials were recorded. Morphologic changes of the optic nerve head were analyzed with stereography, and the ratio of cup area (CA) to disk area (DA) was measured by calculating the number of pixels in each area with a microcomputer. RESULTS: Capillary blood flow in the optic nerve head was continuously below 80% of the baseline throughout the study. The visual-evoked potential latency was significantly delayed in ET-1-treated eyes. The CA/DA ratio was significantly increased relative to baseline in the ET-1 treated eyes. Histologic examination showed axonal loss and demyelination affecting the prelaminar portion of the optic nerve. The intraocular pressure was not significantly different from the control value. CONCLUSION: Optic nerve head ischemia could contribute to the enlargement and excavation of the disk cup independent of the intraocular pressure level.

Animals↗
PubMed2000

Differential taurine effect on outgrowth from goldfish retinal ganglion cells after optic crush or axotomy. Influence of the optic tectum.

The interaction between innervated tissues, targets and nerves is crucial in the maintenance of physiological conditions, and the disturbance of this harmony causes the production of morphological and biochemical changes. After lesion of the optic nerve, several modifications take place in the retina, the optic tectum and the optic nerve. The influence of the tectum on the outgrowth from the goldfish retina and the possible role of taurine was studied. Ganglion retinal cells were identified by retrolabeling with Dil. Crushing the optic nerve 10 days prior to plating retinal cells, as compared with optic axotomy, did not affect the survival of cultured retinal cells, as well as the length of the neurites. However, the number of neurites per cell and the branching of the longest fiber were higher after axotomy than after crushing. The addition of taurine to the medium did not modify this response at 5 days in culture. At early periods in culture, the stimulatory effect on isolated ganglion cell outgrowth produced by taurine was enhanced after axotomy respecting crushing of the optic nerve, but was not affected in retinal explants. The addition of medium from cultured optic tectum several days post-crush of the optic nerve to retinal explants from intact retinas or coming from post-crush retina modified the outgrowth, being inhibitory or stimulatory in a time-dependent manner. The co-culture of optic tectum and retina also affected the outgrowth from the retina with a byphasic shape. The results support the differential response of the retina facing partial or complete interruption with the target and limit the effect of taurine to early periods in culture. In addition, the production of inhibitory factors from the tectum, plus the stimulatory ones, are strongly supported by this work.

Animals↗