Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “OPTICS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,423 records · Page 79Linked to original sources
PubMed1997

Optic disc shape, corneal astigmatism, and amblyopia.

OBJECTIVE: The cornea and the optic disc form the anteroposterior opening of the sclera. This study evaluated whether an abnormal shape of the optic disc is associated with an abnormal configuration of the cornea measured as corneal astigmatism. DESIGN: The study design was a cross-sectional one. PARTICIPANTS: The study included 882 subjects (430 women, 452 men) with a mean age of 45.9 +/- 13.6 years (mean +/- standard deviation; range, 8-87 years) and a mean refractive error of -1.09 +/- 2.76 diopters (range, -21.0 diopters to +7.0 diopters). INTERVENTION: Corneal astigmatism was determined by keratometry, and the optic disc was analyzed morphometrically by planimetric evaluation of optic disc photographs. MAIN OUTCOME MEASURES: Corneal astigmatism, ratio of minimal-to-maximal disc diameter, and optic disc form factor were measured. RESULTS: The amount of corneal astigmatism was significantly (P < 0.001) correlated with an increasingly elongated optic disc shape. Corneal astigmatism was significantly (P < 0.01) higher in eyes with tilted discs. It was significantly (P = 0.006) smaller in eyes with an almost circular disc shape. Amblyopia was significantly (P < 0.05) associated with an elongated optic disc shape and high corneal astigmatism. The axis of corneal astigmatism was correlated with the orientation of the longest disc diameter. The optic disc was significantly (P < 0.05; chi-square test) more often horizontally oval in eyes with a steeper horizontal corneal meridian than in eyes with a steeper vertical corneal meridian. Correspondingly, the disc was significantly (P < 0.05) more often vertically oval in eyes with a steeper vertical corneal meridian than in eyes with a steeper horizontal corneal meridian. CONCLUSIONS: An abnormal optic disc shape is significantly correlated with corneal astigmatism. Especially in young children, if an abnormal optic disc shape is found on routine ophthalmoscopy, refractometry should be performed to rule out corneal astigmatism and to prevent amblyopia. The direction of the longest optic disc diameter can indicate the axis of corneal astigmatism.

Adolescent↗
PubMed1999

Symptomatic compression of the optic nerve by the carotid artery: clinical profile of 18 patients with 24 affected eyes identified by magnetic resonance imaging.

OBJECTIVE: To characterize the clinical features and course of patients with magnetic resonance imaging (MRI)-defined optic nerve compression by the supraclinoid carotid artery. DESIGN: Retrospective, observational case series. PARTICIPANTS: Eighteen patients with 24 affected eyes were identified by reviewing case records from the author's referral-based neuro-ophthalmology practice. Predetermined inclusion and exclusion criteria were applied to potential participants. MAIN OUTCOME MEASURES: The following variables were abstracted from the medical record: age, gender, presenting symptoms, past medical problems, visual acuity, color vision, visual field, pupillary reactions, optic disc appearance, other neurologic signs, and previously documented and follow-up examinations. RESULTS: There were eight women and ten men ranging in age from 28 to 86 years (median age, 72 years) at the time of diagnosis. Ten (56%) of 18 patients had hypertension. Twelve patients had unilateral optic neuropathy, whereas 6 patients had bilateral optic neuropathy. One patient presented with subacute superior orbital fissure syndrome due to mass effect of a dolichoectatic carotid artery. Another patient had oculomotor nerve palsy with signs of aberrant regeneration due to intracavernous mass effect of a dolichoectatic carotid artery. One patient had a bitemporal hemianopia associated with bilateral compression of the immediate prechiasmatic optic nerves by dolichoectatic carotid arteries. The predominant pattern of visual field loss in most patients reflected nerve fiber bundle injury. A central scotoma or absolute central visual field loss was noted in only 6 (25%) of 24 affected eyes. Most patients demonstrated saucerlike excavation of the optic disc. Progression of visual acuity loss occurred at a relatively slow rate. CONCLUSIONS: Although uncommon, intracranial compression of the optic nerve by the carotid artery should be considered in a patient with unexplained or progressive unilateral or bilateral optic neuropathy. This entity can be diagnosed using clinical skills to exclude more common causes of optic nerve injury and coronal-oriented MRI to confirm anatomic compression of the symptomatic optic nerve. Although many affected patients have excavation of the optic disc and nerve fiber bundle visual field defects, most have additional signs atypical for glaucoma, minimizing the potential for diagnostic confusion between the two disorders.

Adult↗
PubMed2000

Exchange transfusion with fluorocarbon for studying synaptically evoked optical signal in rat cortex.

Optical imaging of intrinsic signal is a powerful technique for studying the functional organization of the brain [T. Bonhoeffer, D. S. Kim, D. Malonek, D. Shoham, A. Grinvald, Optical imaging of the layout of functional domains in area 17 and across the area 17/18 border in cat visual cortex, Eur. J. Neurosci. 7 (1995) 1973-1988; M. Hubener, D. Shoham, A. Grinvald, T. Bonhoeffer, Spatial relationships among three columnar systems in cat area 17, J. Neurosci. 17 (1997) 9270-9284; D. Malonek, A. Grinvald, Interactions between electrical activity and cortical microcirculation revealed by imaging spectroscopy: implications for functional brain mapping, Science 272 (1996) 551-554; A. Shmuel, A. Grinvald, Functional organization for direction of motion and its relationship to orientation maps in cat area 18, J. Neurosci. 16 (1996) 6945-6964] [1] [10] [14] [22]. Three components of intrinsic optical signal can be distinguished. Two of these components can be attributed either to changes in blood volume or to changes in oxygen consumption [R.D. Frostig, E.E. Lieke, D.Y. Ts'o, A. Grinvald, Cortical functional architecture and local coupling between neuronal activity and the microcirculation revealed by in vivo high resolution optical imaging of intrinsic signals, Proc. Natl. Acad. Sci. U. S. A. 87 (1990) 6082-6086] [7]. The origin of the third component is not yet clear but the component seems to be based on scattered light [H.U. Dodt, G. D'Arcangelo, E. Pestel, W. Zieglgansberger, The spread of excitation in neocortical columns visualized with infrared-dark field videomicroscopy, NeuroReport 7 (1996) 1553-1558; K. Holthoff, O.W. Witte, Intrinsic optical signals in rat neocortical slices measured with near-infrared dark-field microscopy reveal changes in extracellular space, J. Neurosci. 16 (1996) 2740-2749; B.A. MacVicar, D. Hochman, Imaging of synaptically evoked intrinsic optical signals in hippocampal slices, J. Neurosci. 11 (1991) 1458-1469; L. Trachsel, H.U. Dodt, W. Zieglgansberger, The intrinsic optical signal evoked by chiasm stimulation in the rat suprachiasmatic nuclei exhibits GABAergic day-night variation, Eur. J. Neurosci. 8 (1996) 319-328] [3] [9] [13] [24]. A spectral fitting method with three components is used for the analysis of intrinsic optical signal [M. Nemoto, Y. Nomura, C. Sato, M. Tamura, K. Houkin, I. Koyanagi, H. Abe, Analysis of optical signals evoked by peripheral nerve stimulation in rat somatosensory cortex: dynamic changes in hemoglobin concentration and oxygenation, J. Cereb. Blood Flow Metab. 19 (1999) 246-259] [17]. In order to validate the analysis, we need the knowledge on contribution of signal resulted from hemoglobin to total intrinsic optical signal. The exchange transfusion with fluorocarbon has the advantage that can change the spectral contribution of hemoglobin [M. Ferrari, M.A. Williams, D.A. Wilson, N.V. Thakor, R.J. Traystman, D.F. Hanley, Cat brain cytochrome-c oxidase redox changes induced by hypoxia after blood-fluorocarbon exchange transfusion, Am. J. Physiol. 269 (1995) H417-H424; A.L. Sylvia, C.A. Piantadosi, O(2) dependence of in vivo brain cytochrome redox responses and energy metabolism in bloodless rats, J. Cereb. Blood Flow Metab. 8 (1988) 163-172] [6] [23]. Here we describe a new method of the reduction of hemoglobin signal from somatosensory evoked optical intrinsic signal in rat cortex by the combination of exchange transfusion with fluorocarbon and imaging system of thinned skull cranial window. The method allows for the study of the synaptically evoked changes in light scattering as well as fluorescence of calcium indicator or voltage-sensitive dye without absorption of hemoglobin.

Animals↗
PubMed1996

Ultrasonography of the optic disc cup in discs of various sizes.

PURPOSE: The aim of the study was to evaluate the sensitivity of modern, eye-medicated B-scanners in detecting optic disc cups and to correlate the echographic measurements with an optical assessment. A secondary aim was to correlate the rim-to-rim diameter of the optic disc and the width of the retrobulbar optic nerve on standardised A-scan. METHODS: A prospective study was conducted on 25 emmetropic subjects (50 eyes) with discs and cups of various sizes. They were examined optically by one observer using a high-magnification slit lamp and the 90 D Volk lens. Another observer measured the B-scan dimensions of the disc cups and the retrobulbar optic nerve. Data from the two observers were compared at the end of the study. RESULTS: High resolution B-scan detected optic disc cups of 0.5 mm or larger in all cases. A statistically significant correlation was obtained between echographic measurements and both vertical optical cup disc diameters and cup disc (C:D) ratios (p < 0.0001). Large C:D ratios (0.6 or larger) but small rim-to-rim disc diameter were reported as 'small' on echography. No correlation was found between the measurement of retrobulbar nerve and the diameter of the vertical optical disc diameter. CONCLUSION: Modern, eye-dedicated ultrasonographic scanners are capable of detecting optic disc cups of 0.5 mm or larger. As there is a normal variation in optic disc rim-to-rim diameter, and this cannot be measured using ultrasound, we suggest the reporting of a C:D ratio on the ultrasonography to be potentially misleading. Large disc cups are, however, easily seen and many are likely to be 'pathological'.

Adult↗
PubMed1989

["Morning glory syndrome" and "Handmann's anomaly" in congenital macropapilla. Extreme variants of "confluent optic pits"?].

Seventeen optic disks with morning glory syndrome were measured in absolute and relative size units (millimeters and parapapillary retinal vessel caliber) in 5 and 12 eyes, respectively. Their respective mean areas were 7.47 +/- 2.63 mm2 and 7.84 +/- 4.96 mm2. They were significantly (Mann-Whitney test) larger than 457 unselected normal optic nerve heads (2.69 +/- 0.70 mm2; p less than 0.0001) and 15 optic disks with pits (4.84 +/- 1.42 mm2; p less than 0.001). They are the largest optic nerve heads, probably with constant postnatal size, measured so far, and form part of a spectrum of optic disk anomalies and diseases whose frequency correlates with the size of the optic disk. This spectrum includes abnormally small optic nerve heads with increased prevalence of drusen, pseudopapilledema and nonarteritic anterior ischemic optic neuropathy, asymptomatic macrodisks with physiologic, "pseudoglaucomatous" macrocups, symptomatic macrodisks with pits and, finally, optic nerve heads with morning glory syndrome. The last-mentioned may be considered an extreme variation of optic disks with pits which have combined to form a single macropit covering the entire optic nerve head.

Fluorescein Angiography↗
PubMed2002

Optic neuritis in multiple sclerosis.

PURPOSE: To review the clinical features, natural history, potential pathogenic mechanisms, differential diagnosis, and management of optic neuritis in multiple sclerosis. METHODS: Relevant literature regarding optic neuritis in multiple sclerosis from 1970 to the present was reviewed. RESULTS: Optic neuritis is an acute inflammatory optic neuropathy. It is the most common type of optic neuropathy causing acute visual loss in young adults (peak age at 30-40 years), especially among women. Patients usually present with an acute reduction of visual acuity, orbital pain exacerbated by eye movements, dyschromatopsia, and an afferent papillary defect, with or without swelling of the optic nerve head. Visual field testing most often reveals central defects, but others, such as centrocecal, can also occur. Magnetic resonance image (MRI) scanning of the brain should be undertaken in all cases of acute optic neuritis for diagnostic and prognostic purposes. The brain lesions of multiple sclerosis are commonly seen as T2 ovoid high-signal white matter lesions on MRI scans of the brain located in perivenular regions perpendicular to ventricles with variable enhancement. For atypical presentations of optic neuritis, additional laboratory tests, such as cerebrospinal fluid analysis, serologic tests, and visual evoked potentials, prove to be useful in the diagnosis and subsequent management of the patient. The recommended treatment for optic neuritis is intravenous steroids, as shown in the Optic Neuritis Treatment Trial (ONTT). CONCLUSION: Optic neuritis is often the initial presentation of multiple sclerosis. Recent advances in the understanding of the immune basis for multiple sclerosis has led to earlier and more effective treatment of this disease.

Brain↗
PubMed2005

Localization of endothelin-converting enzyme in bovine optic nerve and retina.

A significant loss and remodeling of the lamina cribrosa tissue leading to the excavation of the optic nerve is seen in glaucoma. Elevated endothelin-1 (ET-1) levels are detected in the aqueous humor of patients of open-angle glaucoma and in the plasma of patients with normal- tension glaucoma. Optic nerve damage, including axonal loss, can be mimicked by ET-1 injection near the optic nerve. ET-1 is produced from its precursor Big ET-1 (38 amino acids) by endothelin-converting enzyme (ECE). Although ET-1 and its receptors have been identified in the retina, little is known of the distribution of ECE at the optic nerve. Presently, ET-1 receptors and Big ET-1 converting activities were characterized in bovine optic nerve and the retina. The ET(B) receptor was detected in both the optic nerve and retina by immunoblotting and cross-linking, using 125I-ET-1. However, the ET(A) receptor was detected only in the retina. Big ET-1 conversion activities were detected in the plasma membrane (PM) of bovine retina, but not in the PM of the optic nerve. The retinal PM Big ET-1 converting activity was inhibited by phosphoramidon, thiorphan, and acidification. Furthermore, ECE cytosolic activities were detected in both the optic nerve and retina. Unlike the PM-ECE, cytosolic Big ET-1 converting activities were activated by acidification (pH 6.4), suggesting the involvement of ECE-2-like activity and/or cathepsin activity. Pepstatin, a potent inhibitor of cathepsins, inhibited the optic nerve (ON) cytosolic conversion of Big ET-1 peptide by 50%, and the combination of pepstatin and phosphoramidon, a potent inhibitor of ECE, inhibited the ON cytosolic activity by 86%. By contrast, the combination of both inhibitors weakly inhibited the cytosolic retinal Big ET-1 converting activity. Western blotting revealed the presence of ECE-1 at the PM of the retina not the ON. ECE-2 and cathpesins B, D, and L were detected only in the cytosol of both the retina and ON. In summary, it appears that ET-1 could be produced in the retina and optic nerve by at least two ECE subtypes and, perhaps, cathepsins. Big ET-1 converting activity may be an important target in preventing ET-1-induced optic nerve pathology.

Animals↗
PubMed1999

A unified paraxial approach to astigmatic optics.

In Gaussian optics properties such as dioptric power, lateral and angular magnification and thickness are simple scalar concepts. In linear optics, the optics of thick astigmatic systems, however, these concepts generalize to three-dimensional concepts in some cases (the dioptric power of thin systems, for example) and to four-dimensional concepts in general. As a result, the quantitative treatment of these properties in astigmatic systems presents challenges to the researcher in optometry, ophthalmology, and vision science. Considerable progress has been made only in the case of dioptric power. This paper presents a generalized approach to astigmatic optics which allows different physical properties to be treated in the same way: the theory is unified and, in a sense, complete. Mathematical and statistical methods developed for treating one concept become directly applicable to others. The paraxial optical properties of any optical system are completely defined by the 4 x 4 ray transfer matrix, called here the (ray) transference. The transference defines four fundamental properties of an optical system, tentatively called here positional magnification, optical thickness, divergence, and directional magnification. They are the four 2 x 2 submatrices A, B, C, and D of the transference. Each fundamental property is a modification of a familiar concept. Divergence is the negative of dioptric power expressed as the dioptric power matrix F. The four fundamental optical properties A, B, C, and D, and the derived property F, despite being different physically, all have the same underlying mathematical structure. This fact is exploited in developing a unified theory. The theory is complete in the sense that the fundamental properties fully characterize the paraxial optics of any system. The paper presents a general treatment that applies to any of the five properties. The implications are far reaching and extend beyond what can be described in the paper. Dioptric power of thin systems is treated as a particular application of the general theory. The result is the resolution of a number of issues of current interest to the researcher. It is shown, for example, that root-mean-squared (curvital) power, root-mean-squared torsional power, and length of the power vector (or dioptric strength) have a Pythagorean relationship, the power vector being the hypotenuse. Mean-squared curvital and torsional powers are in effect the area enclosed by polar profiles of curvital and torsional power, respectively. The full character of dioptric power cannot be represented by a single vector in the usual sense of the term. Two vectors are required: they are the meridional (vector) power and the orthogonal (vector) power, both of which are associated with the reference meridian. The power along a meridian (often thought of as a scalar or as two scalars) is a vector, the meridional power. This meridional power has components along (the meridional component of the meridional power) and perpendicular to (the orthogonal component of the meridional power) the meridian. In the literature, these components are the curvital power and the negative of the torsional power, respectively. The paper also examines the generalization of these results to the dioptric power of thick systems. Dioptric power is not a fundamental optical property but a derived property. Divergence, the negative of dioptric power, is the corresponding fundamental property. The theory described here is ray-based. The concept of the wavefront is unnecessary. The many formulas and concepts that apply in the context of dioptric power apply directly to the fundamental properties as well. The theory has the potential to provide a complete framework for future studies of astigmatic systems and could systematize the approach to and enhance the knowledge of astigmatism.

Astigmatism↗
PubMed2000

New therapies for optic neuropathies: development in experimental models.

Experimental models of human diseases have affected the design and direction of both basic and clinical research into understanding the pathogenesis and treatments of demyelinating disease, stroke, and hereditary disorders of the central nervous system. However, in spite of major advances in molecular research that have linked Leber Hereditary Optic Neuropathy to mutations in mitochondrial DNA, there has been relatively little focus in applying basic scientific methodologies to optic neuropathies other than glaucoma. The relative absence of detailed scientific knowledge about the basic mechanisms involved in the pathogenesis of optic nerve injury has contributed to the use of empiric therapies for neuro-ophthalmic optic neuropathies. Over the past decade major clinical trials, such as the Optic Neuritis Treatment Trial and Ischemic Optic Neuropathy Decompression Trial, have proven that currently available treatment options for demyelinating and ischemic optic neuropathies are ineffective and can even be harmful. Although the pathogenesis of visual failure in demyelinating, ischemic, and hereditary optic neuropathies appears diverse, a final common pathway for irreparable optic nerve injury may exist. This article reviews several models of experimental optic neuropathies that may aid in the development of novel treatments for neuro-ophthalmic disorders of the optic nerve during the 21st century.

Animals↗
PubMed1988

Optic nerve dysfunction in thyroid eye disease: CT.

Optic nerve dysfunction in thyroid eye disease is thought to be due to compression of the optic nerve by enlarged extraocular muscles near the orbital apex. High-resolution computed tomography (CT) scans of 78 orbits of 31 patients with thyroid eye disease were reviewed. Axial scans alone were inadequate for demonstrating compression of the optic nerve. With a coronal reformatted scan from the axial scans, a muscular index was devised and measured to reflect extraocular muscle impingement on the optic nerve. Orbits with optic nerve dysfunction had significantly higher muscular indices than those without optic nerve dysfunction, supporting the hypothesis that optic nerve dysfunction is usually secondary to compression by enlarged extraocular muscles. Muscular indices of 67% or greater in patients with optic nerve dysfunction were diagnostic of compressive optic neuropathy, while muscular indices of less than 50% appeared to exclude optic nerve compression. A single case of optic nerve dysfunction without muscular compression is also discussed.

Exophthalmos↗
PubMed2003

Optic nerve degeneration in a murine model of juvenile ceroid lipofuscinosis.

PURPOSE: To investigate optic nerve degeneration associated with CLN3 deficiency in a murine model of juvenile neuronal ceroid lipofuscinosis (Batten disease). METHODS: Using light and electron microscopy, the density and diameter of axons and the thickness of myelin in optic nerve were compared between age-matched cln3 knock-out (cln3-/-) and wild-type (129ev/TAC) mice. Western blot analysis was used to assay expression of Cln3 in mouse and primate retina and optic nerve. RESULTS: Morphologically identified mast cells were present in the meningeal sheaths surrounding the cln3-/- nerve and in the nerve itself. The cln3-/- optic nerve exhibited an overall loss of uniformity and integrity. Axon density in cln3-/- optic nerve was only 64% of that in wild-type optic nerve (P < 0.01). Accounting for differences in axon density, the diameter of axons in cln3-/- optic nerve was 1.2 times greater than in wild-type optic nerve (P < 0.01). Electron micrographs revealed large spaces between axons and 32% thinner myelin surrounding axons in cln3-/- mice than in wild type (P < 0.01). Western blot analysis demonstrated that Cln3 was expressed in retinas and optic nerves of mouse and primate. CONCLUSIONS: The presence of apparent mast cells in cln3-/- optic nerve suggests compromise of the blood-brain barrier. The absence of Cln3 causes loss of axons, axonal hypertrophy, and a reduction in myelination of retinal ganglion cells. Furthermore, expression of CLN3 in mouse and primate optic nerve links degeneration to loss of Cln3.

Animals↗
PubMed2005

Imaging in breast cancer: diffuse optics in breast cancer: detecting tumors in pre-menopausal women and monitoring neoadjuvant chemotherapy.

Diffuse optical spectroscopy (DOS) and diffuse optical imaging (DOI) are non-invasive diagnostic techniques that employ near-infrared (NIR) light to quantitatively characterize the optical properties of centimeter-thick, multiple-scattering tissues. Although NIR was first applied to breast diaphanography more than 70 years ago, quantitative optical methods employing time- or frequency-domain 'photon migration' technologies have only recently been used for breast imaging. Because their performance is not limited by mammographic density, optical methods can provide new insight regarding tissue functional changes associated with the appearance, progression, and treatment of breast cancer, particularly for younger women and high-risk subjects who may not benefit from conventional imaging methods. This paper reviews the principles of diffuse optics and describes the development of broadband DOS for quantitatively measuring the optical and physiological properties of thick tissues. Clinical results are shown highlighting the sensitivity of diffuse optics to malignant breast tumors in 12 pre-menopausal subjects ranging in age from 30 to 39 years and a patient undergoing neoadjuvant chemotherapy for locally advanced breast cancer. Significant contrast was observed between normal and tumor regions of tissue for deoxy-hemoglobin (p = 0.005), oxy-hemoglobin (p = 0.002), water (p = 0.014), and lipids (p = 0.0003). Tissue hemoglobin saturation was not found to be a reliable parameter for distinguishing between tumor and normal tissues. Optical data were converted into a tissue optical index that decreased 50% within 1 week in response to neoadjuvant chemotherapy. These results suggest a potential role for diffuse optics as a bedside monitoring tool that could aid the development of new strategies for individualized patient care.

Adult↗
PubMed2001

[Optic pathway gliomas in patients with neurofibromatosis type 1: clinical-neuroradiological integrated approach].

PURPOSE: To evaluate a patient population affected by Neurofibromatosis type 1 (NF1) with special reference to optic pathway gliomas. MATERIAL AND METHODS: A total of 419 NF1 patients (222 men, 197 women) were retrospectively evaluated to show incidence, biological behaviour, neuroradiological and clinical presentation of optic pathway gliomas. Central Nervous System MR and ophthalmologic evaluations were reviewed. RESULTS: Thirty-two patients out of 419 (7.6%) showed the presence of optic pathway gliomas. Of these, 28 (87.2%) patients showed tumoral involvement of the optic chiasma. The right intracranial optic nerve was involved in 15 patients (46.8%), the left intracranial optic nerve in 18 (56.2%), the right extracranial optic nerve in 11 (34.3%), the left extracranial optic nerve in 10 (31.2%) and the right and left optic tracts in 6 (18.7%) patients. Geniculate body and optic radiation were not involved by tumour diffusion. Visual acuity testing was positive in 26/32 (81.2%), the fundus oculi in 11/32 (34.3%) patients and the visual field evaluation in 12/32 (37.5%) patients. CONCLUSIONS: In this study we showed an high correlation between optic pathway tumours and ophthalmologic abnormalities confirming the usefulness of an integrated clinical-neuroradiological approach in patients affected by NF1. We also described the biological behaviour of these tumours in our NF1 patient population.

Adolescent↗
PubMed2002

Macroglial alterations after isolated optic nerve sheath fenestration in rabbit.

PURPOSE: To study the modifications undergone by the macroglial cells after meningeal breach of the optic nerve in the rabbit, without optic neuropathy. METHODS: The optic nerve sheath fenestration technique carried out in humans was adapted to rabbit without axonal injury in the optic nerve. The effects of meningeal fenestration on glial cells were examined by immunocytochemical procedures (day 15) using the antibodies against two astrocyte markers: glial fibrillary acidic protein (GFAP) and vimentin. Proliferation of glial cells was evaluated with single 5-bromodeoxyuridine (BrdU) labeling or double GFAP and BrdU labelings. Qualitative data on glial cells were evaluated with the electron microscope. RESULTS: Optic nerve sheath fenestration on healthy adult rabbits resulted in a decrease of volume of the subarachnoid space located at the level of the meningeal scar, with a significant increase of the optic nerve area. The meninges presented a fibrous scar. In the optic nerve parenchyma, astrocytes appeared hypertrophic in the vicinity of the fenestration. The whole nerve contains numerous BrdU-labeled mitotic cells, a number of which double-labeled for both BrdU and GFAP belong to the astrocyte line. There was no loss of optic nerve axons. CONCLUSIONS: The inflammation produced by the surgical breach of the peri-optic meningeal sheaths induces a significant reactivity, including proliferation of astrocytes in the optic nerve. Reactive astrocytes may interact positively with axons and may modify the extracellular environment in the optic nerve.

Animals↗
PubMed2000

Computer-aided 3-D reconstruction and measurement of the optic canal and intracanalicular structures.

OBJECTIVE: To reconstruct the human optic canal and its inner structures, and to provide detailed knowledge of this region for optic nerve decompression for further understanding on the pathologic mechanisms of indirect optic nerve injury. METHODS: Six optic canals and their inner structures were reconstructed using a computer-aided 3-dimensional reconstruction system. Quantitative measurement of the canal wall thickness, bony canal transverse area, optic nerve transverse area, dural sheath transverse area, subarachnoid space transverse area, and subarachnoid space volume were done by means of the computer morphometric analysis system. The detailed spatial relationship among intracanalicular structures were also carefully identified on the 3-D models. RESULTS: The thinnest portion of the canal was the middle part of the medial wall (0.45 +/- 0.35 mm) and the narrowest space was in the middle part of the optic canal (the transverse area was 18.21 +/- 2.50 mm2). The volume of subarachnoid space which can be considered the compensatory space for distention incurred by the hemorrhage, optic nerve edema, or hematoma was 21.16 +/- 4.31 mm3. At the cranial opening, the middle part and orbital opening, its transverse area was 4.45 +/- 1.12 mm2, 2.68 +/- 1.32 mm2 and 1.23 +/- 0.83 mm2, respectively. CONCLUSIONS: Since the compensatory space was limited, even a tiny amount of blood or swelling of the nerve may cause optic nerve compression. Because the narrowest space was in the middle part of the optic canal and the compensatory space for distention gradually decreases from cranial end to orbital end, the middle part and the anterior part of the optic canal and dural sheath are critical in optic nerve decompression.

Eye↗
PubMed1992

Optic nerve head microvasculature of the rabbit eye.

Vascular luminal castings of rabbit eyes were microdissected and studied with scanning electron microscopy to elucidate the three-dimensional angioarchitecture of the optic nerve head. Using sequential microdissection, an incomplete arterial circle was identified as terminal branches of two to three short posterior ciliary arteries around the optic nerve head. Several recurrent branches from the arterial circle form a pial arterial network. This pial system supplies the optic nerve head microvasculature and receives numerous venules from them. The only large vessel to enter the optic nerve is a central retinal artery that has few branches within the optic nerve and provides several branches at the surface of the optic disc. Moderately numerous vessels connect the retinal and ciliary vascular layers within the optic nerve head. Few arterioles to the optic nerve head arise from the choroid; however, there are a small number of capillary and numerous venous connections between them. These results indicate that the principal blood supply of the rabbit optic nerve head is derived from the short posterior ciliary arteries by the arterial circle. The retinal arteries contribute to the surface vasculature of the optic nerve head. The pial system also plays a significant role in both supply and drainage of the rabbit optic nerve head.

Animals↗
PubMed2005

Optical characteristics of waste stabilization ponds: recommendations for monitoring.

The optical character of waste stabilization ponds (WSPs) is of concern for several reasons. Algal photosynthesis, which produces oxygen for waste oxidation in WSPs, is influenced by attenuation of sunlight in ponds. Disinfection in WSPs is influenced by optical characteristics because solar UV exposure usually dominates inactivation. The optical nature of WSPs effluent also affects assimilation by receiving waters. Despite the importance of light behaviour in WSPs, few studies have been made of their optical characteristics. We discuss simple optical measures suitable for routine monitoring of WSPs (including at sites remote from laboratories): optical density of filtrates - an index of dissolved coloured organic (humic) matter, visual clarity - to provide an estimate of the beam attenuation coefficient (a fundamental quantity needed for optical modelling) colour (hue) - as an indicator of general WSP 'condition' and irradiance attenuation quantifying depth of light penetration. The value of optical characterisation of WSPs is illustrated with reference to optical data for WSPs in NZ (including high-rate algal ponds) treating dairy cattle wastewater versus domestic sewage. We encourage increased research on optical characteristics of WSPs and the incorporation of optical measures in monitoring and modelling of WSP performance.

Bioreactors↗
PubMed1996

MR of optic papilla protrusion in patients with high intracranial pressure.

PURPOSE: To evaluate the signal characteristics of the optic papilla (optic nerve head) on routine cranial MR images in patients with clinical evidence of optic papilla elevation caused by high intracranial pressure, and to compare these findings with findings in healthy adult volunteers. METHODS: We reviewed retropectively the MR imaging examinations of 15 patients who were referred with objectively decreased visual acuity and funduscopic findings of optic papilla elevation. T1-weighted and T2-weighted axial MR images were obtained by using conventional spinecho acquisitions on 1.5-T MR imagers. In addition, the MR imaging studies in 10 healthy adult volunteers without visual impairment were reviewed as controls. RESULTS: In 10 (67%) of the 15 patients, visual elevation of the optic papilla was shown by MR imaging. In all 15 patients, the MR signal intensity of the optic papilla was hypointense relative to the vitreous of the globe on T2-weighted images. In the healthy volunteer group, the optic papillae were all similarly hypointense relative to the vitreous of the globe on T2-weighted images; however, these optic papillae were flat. CONCLUSION: Clinical examination and MR imaging may show elevation of the optic papilla in patients with high intracranial pressure. When chronic, optic papilla elevation has been shown to correlate well with severe loss of vision. Actual edema of the optic papilla seems to play little role in the physical elevation observed clinically in the chronic stages of this pathologic process.

Adolescent↗