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 253 records · Page 14Linked to original sources
PubMed1995

Quantitative analysis of optic disc cupping in compressive optic neuropathy.

PURPOSE: Cupping of the optic disc, a characteristic sign of glaucoma, has been anecdotally described in association with compressive optic neuropathy. The aim of this study is to perform a masked, controlled, and quantitative measurement of the optic disc cup to determine if compressive lesions of the afferent visual pathway were associated with increased cupping. METHODS: The ratio of cup area:disc area of 29 patients with intracranial lesions impinging on the optic nerves and the chiasm (14 with pituitary adenomas, 7 with meningiomas, 6 with craniopharyngiomas, and 2 with aneurysms) was compared with those of 20 age-matched control subjects. The areal ratios were derived planimetrically from hand-drawn images of magnified stereophotographs. Patients were divided into three groups based on the degree of laterality of visual compromise. Uninvolved eyes served as an internal control for patients with unilateral disease. RESULTS: The median ratio of cup area:disc area was 0.37 for all eyes with visual compromise (n = 51) and 0.10 for control eyes, which was statistically significant (P = 0.0001). The median intereye difference in the ratio of cup area:disc area was 0.13 for patients with unilateral lesions and 0.04 for control subjects. This difference also was statistically significant (P = 0.0001). CONCLUSIONS: The finding of intereye asymmetry in patients with unilateral optic nerve compression is convincing evidence that the enlarged cup is an acquired feature. Several types of compressive lesions of the anterior visual pathway can be associated with increased cupping of the optic disc in the absence of increased intraocular pressure.

Adolescent↗
PubMed1996

Analysis of signal propagation in optically coupled detectors for digital mammography: II. Lens and fibre optics.

An x-ray detector for digital x-ray mammography is under investigation, which consists of a phosphor screen coupled by a demagnifying fibre-optic taper to a time-delay integration mode, charge-coupled device (CCD) image array. The signal propagation through such a detector depends on the intensity and angular emission of light from the phosphor screen, the angular acceptance and transmission of light through the optics, and the spectral sensitivity of the CCD to the fluorescent light. The production of light by the phosphor screen was considered in a previous paper. Here, the issues related to the optics are examined. For phosphor screens coupled by lenses with limiting acceptance angles of less than 30 degrees, it was calculated that the coupling efficiency would be 10% greater than would be estimated under the assumption of a Lambertian source. These increases occur because a phosphor screen typically produces light which is more forward directed than a Lambertian source. Similar increases in efficiency are observed when a phosphor screen is coupled to a fibre-optic faceplate or taper. For fibre optics, exact estimation of the optical coupling efficiency requires knowledge of the angular-dependent transmission efficiency of the fibres.

Biophysical Phenomena↗
PubMed1989

Optic disc morphometry in simple optic nerve atrophy.

This study was undertaken to evaluate the optic disc changes in eyes with non-glaucomatous optic nerve damage. The intra- and parapapillary region was evaluated morphometrically in 106 eyes of 56 patients with simple optic nerve atrophy (SONA) and in 107 normal eyes of 57 subjects. Colour stereo optic disc diapositives were used. Only one randomly chosen eye per subject and patient was taken for statistical analysis. Characteristics of SONA were: decreased visibility of the parapapillary retinal nerve fibers, diminished retinal vessel diameter, and area with pallor larger than area with cupping. Size and form of the optic disc, neuroretinal rim, peripapillary scleral ring, and zone Alpha and Beta of the parapillary chorioretinal atrophy were not significantly different. Also, distinctness of a tesselated fundus, frequency of optic disc haemorrhages and frequency of bared circumlinear or bared cilioretinal vessels did not differ significantly. These morphologic features are helpful in the diagnosis and differential diagnosis of SONA.

Adult↗
PubMed1971

Vasopressin test in cases of optic atrophy and optic neuritis.

The vasopressin test gave pathological results in 12 cases of optic atrophy and normal results in three cases. One of the patients with a pathological response had Leber's disease and three had tobacco-alcholic amblyopia, while in the rest the optic atrophy was of uncertain origin. In the cases with normal results the aetiology was also unclear. The Metopirone test was normal in 13 cases and pathological in only one case of optic atrophy. In three out of five patients with optic neuritis the vasopressin test gave pathological responses. The high frequency of pathological vasopressin tests in patients with optic lesions indicates a simultaneous disturbance of the hypothalamo-hypophyseal function. The background to this might be a disturbed vascular supply. The vasopressin test was of no help in diagnosing tumours as a cause of optic atrophy.

Adolescent↗
PubMed1997

The 5-year risk of MS after optic neuritis. Experience of the optic neuritis treatment trial.

The objective of our study was to assess the 5-year risk of and prognostic factors for the development of clinically definite multiple sclerosis (CDMS) following optic neuritis. In a prospective cohort study design, 388 patients, who did not have probable or definite MS at study entry enrolled in the Optic Neuritis Treatment Trial between 1988 and 1991, and were followed for the development of CDMS. The 5-year cumulative probability of CDMS was 30% and did not differ by treatment group. Neurologic impairment in the patients who developed CDMS was generally mild. Brain MRI performed at study entry was a strong predictor of CDMS, with the 5-year risk of CDMS ranging from 16% in the 202 patients with no MRI lesions to 51% in the 89 patients with three or more MRI lesions. Independent of brain MRI, the presence of prior nonspecific neurologic symptoms was also predictive of the development of CDMS. Lack of pain, the presence of optic disk swelling, and mild visual acuity loss were features of the optic neuritis associated with a low risk of CDMS among the 189 patients who had no brain MRI lesions and no history of neurologic symptoms or optic neuritis in the fellow eye. The 5-year risk of CDMS following optic neuritis is highly dependent on the number of lesions present on brain MRI. However, even a normal brain MRI does not preclude the development of CDMS. In these patients with no brain MRI lesions, certain clinical features identify a subgroup with a particularly low 5-year risk of CDMS.

Adult↗
PubMed2006

Application of micro-attenuated total reflectance infrared spectroscopy to quantitative analysis of optical fiber coatings: effects of optical contact.

Micro-attenuated total reflectance (ATR) infrared spectroscopy is one of the few methods applicable for an in situ analysis of polymer coatings. In this method, the information is collected using an internal reflection element (IRE), which is brought into contact with the coated substrate. Perfect optical contact is hardly achievable for non-flat substrates and/or for those samples that cannot be well aligned with respect to the IRE. Consequently, the infrared peak intensities, their ratios, and all quantities calculated from the spectra become dependent upon the optical contact quality. In this work, we suggest a model that describes the peak intensities in terms of the optical contact. As an illustration, we apply this model to polymer-coated optical fibers. Relatively small diameters of tested fibers and their cylindrical shape result in imperfect optical contact between the sample and the IRE. Spectroscopic approaches of determining the degree of cure of polymer coatings are analyzed in view of the obtained results. Ways of minimizing the error induced by imperfect optical contact are suggested.

Absorption↗
PubMed1999

Spatial relationship of motion automated perimetry and optic disc topography in patients with glaucomatous optic neuropathy.

PURPOSE: To compare the spatial relationship of focal motion automated perimetry (MAP) visual field defect with focal defect in optic disc topography. METHODS: Patients (n = 12) with focal MAP visual field loss and focal change in optic disc topography were studied. The MAP visual field was divided into 12 field zones representing retinal nerve fiber layer arcuate bundles. Zones of MAP loss were related to rim area ratio (RAR), which was obtained by dividing the rim area, measured by the Heidelberg Retina Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany), into 36 10 degrees sectors and then dividing the area of each sector by the total rim area for each subject. Rim area ratio was compared to a normative database (n = 76) to quantify change in optic disc topography. In these same patients, the spatial relationship between standard automated perimetry (SAP) and short-wavelength perimetry (SWAP) and optic disc topography was also assessed. RESULTS: Motion automated perimetry superior visual field zones 14 through 19 were most often associated with a reduction in RAR for inferior sectors 24 through 29, and inferior visual field zones 4 through 7 were most often associated with a reduction in RAR for superior temporal sectors 11 through 16. Similar spatial relationships were found between SWAP and SAP and the RAR. CONCLUSION: Focal MAP visual field loss and focal changes in optic disc topography are spatially related. This relationship is similar to that found between SWAP and SAP with optic disc topography. Focal thinning or notching detected by RAR analysis might be independent of the specific functional test employed.

Glaucoma, Open-Angle↗
PubMedDate not supplied

Contrast-enhanced MR imaging of optic nerve lesions in patients with acute optic neuritis.

The purpose of this study was to determine if administration of gadopentetate dimeglumine aids in the MR detection of optic nerve lesions in patients with acute optic neuritis and to establish an efficient MR imaging protocol to effectively demonstrate such lesions. Patients with acutely decreased visual acuity were referred for MR imaging of the brain and orbits. Predominantly, T1-weighted images were obtained in axial and coronal planes with and without contrast administration. Enhancing lesions were observed in the optic nerve (7/14 patients) and optic chiasm (2/14), and associated white matter lesions were seen elsewhere in the brain (5/19). Our results indicate that administration of gadopentetate dimeglumine aids in the MR detection of lesions of the optic nerve and optic chiasm. Applicability of our MR imaging protocol was confirmed by the demonstration of these lesions and by the disseminated white matter lesions seen simultaneously elsewhere in the brain.

Acute Disease↗
PubMed1985

Optic disc edema with aphakic cystoid maculopathy masquerading as ischemic optic neuropathy.

Two patients with visual loss after cataract extraction were found to have prominent pallid optic disc edema, peripapillary hemorrhage, and cystoid maculopathy. A diagnosis of anterior ischemic optic neuropathy, with coincidental aphakic cystoid macular edema, was initially considered. The clinical course, however, favored a diagnosis of visual loss secondary to maculopathy. In both cases, fluorescein angiography disclosed leakage of fluorescein dye from macula, optic disc, and peripapillary foci. Fluorescein angiography and stereo color photographs of 51 patients with aphakic cystoid maculopathy were reviewed to determine the incidence of optic disc edema. Although optic disc swelling was rarely recognized on fundus photography, optic disc hyperfluorescence was observed in 75% of cases.

Aged↗
PubMed1986

Microtubule-associated protein 2 (MAP2) is present in astrocytes of the optic nerve but absent from astrocytes of the optic tract.

Using the peroxidase-antiperoxidase staining technique at the light- and electron-microscope levels and two monoclonal antibodies against microtubule-associated protein 2 (MAP2), we found that astrocytes located at the periphery of the rat optic nerve were strongly stained, while those in the central region were very weakly stained. MAP2 immunoreactivity was present in astrocytes of the optic chiasm, but was absent from astrocytes in the optic tract. Inside astrocytes, MAP2 immunoreactivity was excluded from bundles of glial filaments. Treatment of animals with beta,beta'-iminodipropionitrile (IDPN), which caused axonal atrophy, enhanced the staining intensity of all optic nerve astrocytes. Axons and oligodendrocytes remained unstained. Using PAGE and Western immunoblots, we found that extracts from bovine optic nerve contained MAP2. Astrocytes in any other region of the nervous system were negative for MAP2 immunoreactivity, except of the pituicytes and the astrocytes of the fimbria of hippocampus. The optic nerve, neurohypophysis, and hippocampal fimbria are white matter tracts that travel unsupported and free of surrounding nervous tissue. These findings suggest that MAP2 is expressed in astrocytes that are under excessive mechanical stress and further indicate that MAP2 may function as a cytoskeletal rigidifying agent in certain cells.

Animals↗
PubMed1984

Ischemic optic neuropathy associated with optic disc drusen.

Ischemic optic neuropathy developed in five eyes of four patients with optic nerve drusen. Two of the patients were in their 20s, a decade when idiopathic ischemic optic neuropathy is rare. This argues against a chance concurrence of drusen and idiopathic ischemic optic neuropathy. Infarction of the distal portion of the optic nerve in patients with drusen may result from mechanical distortion of blood vessels in the laminar and prelaminar regions.

Adult↗
PubMed1991

The origin of pain in optic neuritis. Determinants of pain in 101 eyes with optic neuritis.

In 101 eyes with either anterior or retrobulbar optic neuropathy of ischemic or inflammatory origin, ocular pain occurred significantly more often with retrobulbar optic neuropathy. The association of pain with posterior optic nerve lesions supports Whitnall's hypothesis that the pain of optic nerve inflammation is caused by traction of the origins of the superior and medial recti on the optic nerve sheath at the orbital apex. Eye pain reflected neither severity nor origin of optic neuropathy.

Adult↗
PubMed1987

Morphological response of injured adult rabbit optic nerve to implants containing media conditioned by growing optic nerves.

Adult rabbit retina can express regeneration-associated characteristics after optic nerve injury, provided it is supplied with appropriate diffusible substances originating from media conditioned by regenerating fish optic nerves or by optic nerves of a newborn rabbit [Hadani et al., Proc. Natl. Acad. Sci. U.S.A., 81 (1984) 7965; Schwartz et al., Science, 228 (1985) 600]. This was shown by applying the active substances to the injured axons in the form of 'wrap-around' implants, consisting of collagen-coated silicone tubes which had been soaked in the conditioned media (CM). The regeneration-associated response was manifested biochemically and by sprouting of nerve fibers in culture. The present work provides morphological evidence that the implantation prolongs survival of ganglion cells and optic nerve fibers and induces new growth. Light microscopic analysis (using horseradish peroxidase (HRP) for labeling the fibers) revealed, 1 week following optic nerve injury, labeled fibers and ganglion cells in both the implanted and control (injured only or injured and implanted with collagen-coated silicone tubes free of CM) nerves. However, from the second week after the injury, distinct differences in the appearance of viable ganglion cells and labeled fibers, were seen between experimental and control preparations. In sections taken through the optic nerve, at the region distal to the site of injury, HRP-labeled fibers were seen in the experimental nerves 1 week, 2 weeks and to a significantly lesser extent 1 month after injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Immunological evidence that the neural adhesion molecule L1 is expressed in fish brain and optic nerve: possible association with optic nerve regeneration.

In the mammalian peripheral nervous system (PNS), expression of the neural adhesion molecule L1 on Schwann cells and neurons has been correlated with axonal growth during development and regeneration. The present study was undertaken to examine whether a similar correlation exists between a lesion-induced increase of L1 expression and regenerative capacity in the central nervous system (CNS). The fish optic nerve was used as a model for a successfully regenerating region of the CNS. Immunochemical and immunohistological experiments carried out with immunoaffinity purified polyclonal antibodies, generated against L1 from mouse brain, showed that carp optic nerve and brain, but not liver, contained L1 immunoreactivity. Western blot analysis of brain tissue yielded one distinct band at 200 kDa, while a double band at 200 kDa and two low-molecular weight bands at 120 and 100 kDa, possibly degradation products, were seen in the optic nerve. Immunohistological examination of normal optic nerves revealed L1 immunoreactivity, predominantly associated with connective tissue boundaries of nerve fascicles and with blood vessels, as well as inside axonal fascicles. L1 immunoreactivity was increased by 25%, 8 days after crushing of the optic nerve, as determined by radioimmunoassay on a nerve segment distal to the site of injury and compared with untreated control nerves. Increased levels of L1 were also seen by immunohistology and found to be predominantly associated, as in the normal nerve, with connective tissue boundaries and blood vessels. These observations suggest that a lesion-induced increase in L1 expression in the fish optic nerve is associated with axonal regrowth in the CNS.

Animals↗
PubMed1992

Effects of lesions of the optic nerve, optic tectum and nervus terminalis on rod precursor proliferation in the goldfish retina.

Teleost retinas grow throughout life by proliferation of neuroblasts at the retinal margin and dedicated rod precursors in the outer nuclear layer. Mechanisms regulating this proliferation are largely unknown. Previous investigators observed that rod precursor replication, as detected by incorporation of radioactive thymidine into cells of the outer nuclear layer, is enhanced after optic nerve crush. We attempted to determine whether this was due to severing of the retinopetal (nervus terminalis, n.t.) or retinofugal (retinal ganglion cell) axons in the optic nerve of the goldfish, Carassius auratus. In the first series of experiments, we ablated unilaterally the optic nerve, olfactory bulb (containing n.t. ganglia), or optic tectum (containing retinal ganglion cell axons and n.t. collaterals). Rod precursor proliferation increased dramatically in both retinas as soon as 5 days after surgery; in addition, the numbers of dividing cells were greater in the ipsilateral retina 10-15 days after optic nerve crush or tectal ablation and in the contralateral retina 20-25 days after olfactory bulb ablation. These observations are not accounted for by the known projections of retinal ganglion cells, but are consistent with the projections of the n.t. In the second series of experiments, n.t. projections to the brain and retina were severed bilaterally 7-8 weeks before the unilateral optic nerve crush or hemitectal ablation. Rod precursor proliferation increased as before, but the quantities of dividing cells were always equal in both retinas. We conclude that the n.t. may modulate rod proliferation locally and that injury to (some) brain regions may cause release of mitogens that affect rod precursors in both retinas.

Animals↗
PubMed2005

Measurement of the optical parameters of purple membrane and plant light-harvesting complex films with optical waveguide lightmode spectroscopy.

Purple membrane (bacteriorhodopsin) and plant light-harvesting complexes (LHCII) were dried on the optical waveguide sensor with varying thicknesses in a wide range (from 20 to several hundreds of nanometers) and the optical parameters were studied with optical waveguide lightmode spectroscopy. It was found that applying the approximate 4-layer mode equations for the measured effective refractive indices resulted in unacceptable results for the optical parameters: with increasing thickness the refractive index decreased monotonously from 1.5 to 1.1. Therefore an inverse waveguide numerical method was developed and used to obtain reliable results from the experiments. The inverse method yielded an approximately constant (1.53) refractive index independently of the thickness for the purple membrane and LHCII films. Light-induced changes in the optical parameters of the purple membrane and LHCII films were also studied. For purple membrane films the most significant effect is the change in refractive index and absorption. For LHCII films prolonged illumination induced irreversible structural changes, most probably of thermo-optic origin.

Biosensing Techniques↗
PubMed1993

Fellow eye abnormalities in acute unilateral optic neuritis. Experience of the optic neuritis treatment trial.

BACKGROUND: Visual function in the fellow eye at the onset of unilateral optic neuritis has not been systematically evaluated. The authors prospectively determined the prevalence of abnormalities in the fellow eyes of the 448 eligible patients entered into the Optic Neuritis Treatment Trial. METHODS: All patients underwent testing of visual acuity, contrast sensitivity, color vision, and visual field, as well as magnetic resonance imaging (MRI) of the brain and a neurologic examination. RESULTS: Abnormalities in the fellow eye were found on measurement of visual acuity in 13.8%, contrast sensitivity in 15.4%, color vision in 21.7%, and visual field in 48.0% of patients. The majority of the fellow eye deficits resolved over several months. A higher prevalence of MRI changes consistent with demyelination of the brain was found in patients with a past history of optic neuritis in the fellow eye compared with patients without such a history (P = 0.004). Patients with abnormal fellow eyes but no history of previous optic neuritis were no more likely to have clinical (P = 0.658) or MRI evidence (P = 0.166) of multiple sclerosis than patients with normal fellow eyes. CONCLUSIONS: The improvement of many of the visual deficits indicates that visual abnormalities detected in the fellow eye at the onset of symptomatically unilateral optic neuritis may not represent preexisting optic nerve demyelination. Whether the presence of these deficits is predictive of the development of clinical multiple sclerosis cannot be determined at this time.

Acute Disease↗
PubMed1997

Netrin-1 and DCC mediate axon guidance locally at the optic disc: loss of function leads to optic nerve hypoplasia.

Embryonic retinal ganglion cell (RGC) axons must extend toward and grow through the optic disc to exit the eye into the optic nerve. In the embryonic mouse eye, we found that immunoreactivity for the axon guidance molecule netrin-1 was specifically on neuroepithelial cells at the disk surrounding exiting RGC axons, and RGC axons express the netrin receptor, DCC (deleted in colorectal cancer). In vitro, anti-DCC antibodies reduced RGC neurite outgrowth responses to netrin-1. In netrin-1- and DCC-deficient embryos, RGC axon pathfinding to the disc was unaffected; however, axons failed to exit into the optic nerve, resulting in optic nerve hypoplasia. Thus, netrin-1 through DCC appears to guide RGC axons locally at the optic disc rather than at long range, apparently reflecting the localization of netrin-1 protein to the vicinity of netrin-1-producing cells at the optic disc.

Animals↗