PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “OPTICS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 37 records · Page 2Linked to original sources
PubMed1981

Residual tectal projection from the contralateral central retina of the frog after homolateral optic nerve and main optic tract section. A possible input from the axial optic tract.

After homolateral (right) optic nerve and main optic tract section a residual visual activity originating from the contralateral (left) central retina was recorded in the right optic tectum. Units were classified in three groups according to their receptive field properties: (1) slow-adapting units analogous to class 3 retinal ganglion cells; (2) fast-adapting postsynaptic units; (3) visual neurons. All of these units have in common a receptive field located near the projection of the left eye optic axis. Evidence that these units belong to the same visual pathway (i.e., the axial optic tract) is discussed.

Action Potentials↗
PubMed1995

Optic nerve decompression surgery for nonarteritic anterior ischemic optic neuropathy (NAION) is not effective and may be harmful. The Ischemic Optic Neuropathy Decompression Trial Research Group.

OBJECTIVE: To assess the safety and efficacy of optic nerve decompression surgery compared with careful follow-up alone in patients with nonarteritic anterior ischemic optic neuropathy (NAION). DESIGN: The Ischemic Optic Neuropathy Decompression Trial (IONDT) is a randomized, single-masked, multicenter trial. SETTING: Twenty-five US clinical centers. PARTICIPANTS: The IONDT ceased recruitment on October 20, 1994, on the recommendation of its Data and Safety Monitoring Committee. The preliminary results presented herein are based on data as of September 8, 1994, from 244 patients with NAION and visual acuity of 20/64 or worse. One hundred twenty-five patients had been randomized to careful follow-up, and 119 had been randomized to surgery, with 91 and 95, respectively, having completed 6 months of follow-up. INTERVENTION: Patients in the surgery group received optic nerve decompression surgery and follow-up ophthalmologic examinations; those in the careful follow-up group received ophthalmologic examinations at the same times as the surgery group. MAIN OUTCOME MEASURES: Gain or loss of three or more lines of visual acuity on the New York Lighthouse chart at 6 months after randomization, as measured by a technician masked to treatment assignment. RESULTS: Patients assigned to surgery did no better when compared with patients assigned to careful follow-up regarding improved visual acuity of three or more lines at 6 months: 32.6% of the surgery group improved compared with 42.7% of the careful follow-up group. The odds ratio (OR) for three or more lines better, adjusted for baseline visual acuity and diabetes, was 0.74 (95% confidence interval [CI], 0.39 to 1.38). Patients receiving surgery had a significantly greater risk of losing three or more lines of vision at 6 months: 23.9% in the surgery group worsened compared with 12.4% in the careful follow-up group. The 6-month adjusted OR for three or more lines worse was 1.96 (95% CI, 0.87 to 4.41). No difference in treatment effect was observed between patients with progressive NAION and all others. CONCLUSION: Results from the IONDT indicate that optic nerve decompression surgery for NAION is not effective, may be harmful, and should be abandoned. The spontaneous improvement rate is better than previously reported.

Aged↗
PubMed1993

Micromanipulation of chromosomes in PTK2 cells using laser microsurgery (optical scalpel) in combination with laser-induced optical force (optical tweezers).

An optical scalpel and optical tweezer have been combined to perform intracellular microsurgery and micromanipulation in vivo. When only laser microsurgery was performed on metaphase chromosomes, the dissected sister chromatid fragments drifted off to either the side of the spindle or completely off the spindle. At anaphase the fragments separated and the two arms generally moved to their respective daughter cells. When the chromosome arm was cut during anaphase A and B, the distal chromosome fragment separated from the rest of the chromosome and moved toward the pole, following the proximal chromosome fragment. Distal chromosome fragments laser-dissected during metaphase were held together throughout anaphase using the optical trap. Optical trapping of dissected chromosome fragments during anaphase A and B inhibited movement of the chromosome fragment to its pole. As a result, the trapped chromosome fragments were (1) incorporated into the opposite daughter cell, (2) lost in the cleavage furrow during cytokinesis, or (3) eventually incorporated into the correct daughter cell. These results indicate that optical traps are effective in holding laser-dissected chromosome fragments throughout mitosis. This new tool should be useful for studies on chromosome movement and cell genetics.

Animals↗
PubMed2006

Optimization of the input losses in fiber-optic communications with an acousto-optic all-optical switch.

We study optical losses in the single-mode fiber system with an all-optical switch based on the anisotropic acousto-optic (AO) TeO(2) 2D deflector. It is shown, theoretically and experimentally, that the mismatch of the output-fiber mode profile and the switched optical beam shape depends significantly on the monochromaticity of the light beam and is determined by the frequency dispersion of the laser beam diffracted on a Bragg AO cell. A quantitative analysis of the dependence of the input optical losses on the spectral width of the light beam is presented.

Journal Article↗
PubMed2001

Optic cup enlargement followed by reduced optic nerve head circulation after optic nerve stimulation.

PURPOSE: To investigate changes in optic nerve head (ONH) circulation, visual evoked potentials (VEPs), and ONH cupping after stimulation of the optic nerve. METHODS: Electrodes were fixed above the optic chiasma in rabbits under general anesthesia. Screw-type electrodes for VEP recording were fixed on the dura. ONH circulation, intraocular pressure (IOP), and blood pressure (BP) were measured after the passage of a current of 0.1 mA for 0.1 second (weak stimulation), 1 mA for 1 second (moderate), 5 mA for 10 seconds (strong), or 25 mA for 10 seconds (severe). Normalized blur (NB), indicative of tissue blood flow and velocity, was measured in the ONH after each stimulation, by using a laser speckle circulation analyzer. Changes in VEP and ocular fundus were also recorded. The ratio of cup area (CA) to disc area (DA) was measured before and 4 weeks after stimulation. After all experiments, the ONH was histologically examined. RESULTS: Weak stimulation increased NB in ONH for 10 minutes, whereas strong or severe stimulation significantly decreased NB for a longer time, in a dose-dependent manner. BP showed no significant change, except with severe stimulation. IOP was not significantly changed. VEP amplitude was reduced 30 minutes after strong stimulation. The CA-to-DA ratio was significantly increased 4 weeks after strong stimulation. In some rabbits, disc hemorrhage occurred, followed by enlargement of disc cupping, with slight gliosis. CONCLUSIONS: Electrical stimulation of the optic nerve changed ONH circulation and VEPs and increased disc cupping. This technique warrants further investigation as an experimental model for normal-tension glaucoma.

Animals↗
PubMed1991

The clinical profile of optic neuritis. Experience of the Optic Neuritis Treatment Trial. Optic Neuritis Study Group.

The baseline characteristics of 448 eligible patients entered into the Optic Neuritis Treatment Trial are described in an effort to summarize the clinical profile of acute optic neuritis. A total of 77.2% of the patients were women. Mean age was 31.8 years. Pain accompanied the visual loss in 92.2% of cases. The optic disc appeared swollen in 35.3% of the patients and normal in 64.7%. A wide variety of visual field defects were present. Abnormalities in asymptomatic fellow eyes were noted, particularly on perimetry. Magnetic resonance imaging showed changes consistent with demyelination of the brain in 48.7% of the patients. Magnetic resonance imaging, serologic studies (such as the antinuclear antibody test and the fluorescent treponemal antibody absorption test), chest roentgenography, and lumbar puncture were of limited utility in defining a cause for visual loss other than optic neuritis associated with demyelinative disease.

Adolescent↗
PubMed1999

[Intra-orbital decompression of the optic nerve by opening the peri-optic meninges in the treatment of severe optic neuropathies complicating benign intracranial hypertension].

Papilledema from benign intracranial hypertension can cause severe loss of visual acuity and visual field, with an optic neuropathy. We report a study of 5 patients with benign intracranial hypertension, and severe visual loss (visual field loss and visual acuity reduced to 1/10 or less) not improved by medical therapy (acetazolamide). We performed unilateral orbital decompression of the optic nerve sheath. No major operative complication was noted. Follow-up ranged from 11 months to 23 months, with an average of sixteen months. Visual function improvement was noted within 3 months after operation in 4 patients (for 2 eyes on the surgical side improvement of 2/10 and 5/10, for 3 eyes on the opposite surgical side average improvement of 4.6/10). The other patient showed improvement, but no significant. Optic nerve sheath decompression in benign intracranial hypertension seems to be a safe procedure and a therapeutic option in the management of raised intracranial pressure complicated by optic neuropathy with severe visual loss.

Acetazolamide↗
PubMedDate not supplied

The optic syrinx: cavernous degeneration of the optic nerve demonstrated by iopamidol optic neurography.

Cavernous degeneration of the optic nerve has been described predominantly in association with long-standing glaucoma, although less frequently it has been reported in other, disparate disease processes. The only descriptions to date have been in pathologic specimens in vitro. This is the first report to describe syrinx formation of the optic nerves in vivo in two patients with nonglaucomatous conditions affecting the optic nerves.

Adolescent↗
PubMed2006

X-Shaped electro-optic chromophore with remarkably blue-shifted optical absorption. Synthesis, characterization, linear/nonlinear optical properties, self-assembly, and thin film microstructural characteristics.

A novel type of "X-shaped" two-dimensional electro-optic (EO) chromophore with extended conjugation has been synthesized and characterized. This chromophore is found to exhibit a remarkably blue-shifted optical maximum (357 nm in CH(2)Cl(2)) while maintaining a very large first hyperpolarizability (beta). Hyper-Rayleigh Scattering (HRS) measurements at 800 nm provide a beta(zzz) value of 1840 x 10(-30) esu. Self-assembled thin films of this chromophore were fabricated via a layer-by-layer chemisorptive siloxane-based approach. The chromophoric multilayers have been characterized by transmission optical spectroscopy, advancing contact angle measurements, synchrotron X-ray reflectivity, atomic force microscopy, and angle-dependent polarized second harmonic generation spectroscopy. The self-assembled chromophoric films exhibit a dramatically blue-shifted optical maximum (325 nm) while maintaining a large EO response (chi(2)(333) approximately 232 pm/V at 1064 nm; r(33) approximately 45 pm/V at 1310 nm). This work demonstrates an attractive approach to developing EO materials offering improved nonlinearity-transparency trade-offs.

Journal Article↗
PubMed1998

[Measurement for optical nonlinearity and optical bistability in II - VI semiconductor by optical waveguide method].

The untransparent substrates on the epitaxial layer need not be etched out from chemistry etching to prepare the "window" through light. The optical absorption, optical nonlinearities and optical bistabilities of the semiconductor thin films with the nanostructure grown on the untransparent substrates can be directly measured by the end face coupling method of optical waveguide. Meanwhile, the several experiment examples of II - VI single crystal thin films and superlattices grown on GaAs substrate are demonstrated in this paper.

English Abstract↗
PubMed1996

Presence of LHRH (luteinizing hormone-releasing hormone) fibers in the optic nerve, optic chiasm and optic tract of the adult rat.

In mammals LHRH (luteinizing hormone-releasing hormone) is synthesized and released by a set of neurons that have their embryonic origin in the olfactory placode. We have observed that, besides their classical location, LHRH fibers can also be seen in the optic nerve and optic chiasm. Some LHRH fibers could also be traced in the optic tract. The possible course of these projections, and their functional significance are discussed.

Age Factors↗
PubMed2001

The SKILL Card test in optic neuritis: experience of the Optic Neuritis Treatment Trial. Smith-Kettlewell Institute Low Luminance. Optic Neuritis Study Group.

OBJECTIVES: To assess the value of the Smith-Kettlewell Institute Low Luminance (SKILL) Card test, designed to measure vision at reduced contrast and luminance, among patients with previous optic neuritis. MATERIALS AND METHODS: The SKILL Card test was administered to 295 patients participating in the Optic Neuritis Treatment Trial (ONTT) follow-up study, concurrent with measurement of visual acuity, visual field, contrast sensitivity, and color vision. Health-related quality of life (HRQL) was also assessed in a subset of patients using the National Eye Institute Visual Function Questionnaire and an ONTT-developed questionnaire. RESULTS: The SKILL Card difference score (high-contrast acuity score minus low-contrast acuity score) was only weakly associated with the other measures of vision function (rs absolute range, 0.05-0.31) and with the HRQL measures (rs absolute range, 0.02-0.15). In contrast, the light and dark component scores of the SKILL Card test had higher associations with the other vision measures (rs absolute range, 0.27-0.54) and with the HRQL measures (rs absolute range, 0.10-0.40). CONCLUSIONS: The SKILL Card difference score is not a meaningful measure for patients with optic neuritis; however, the test appears to have clinical usefulness as a method to measure high-contrast and low-contrast acuity.

Adolescent↗
PubMed1992

GABAergic and non-GABAergic projections of accessory optic nuclei, including the visual tegmental relay zone, to the nucleus of the optic tract and dorsal terminal accessory optic nucleus in rat.

This study examines the non-gamma-amino butyric acid (GABA)ergic (group I neurons) and GABAergic neurons (group II neurons) of the accessory optic system projecting to the nucleus of the optic tract (NOT)/dorsal terminal nucleus (DTN) of the accessory optic system in rat. These nuclei include the dorsal (MTNd) and ventral (MTNv) divisions of the medial terminal nucleus, the lateral terminal nucleus, the interstitial nucleus of the superior fasciculus, the posterior fibers, and the visual tegmental relay zone. GABAergic neurons of these nuclei that do not target the NOT/DTN (group III neurons) have also been observed. The fluorescent retrograde tracer fluoro-gold was injected into the pretectum, targeting the NOT/DTN and the tissue prepared immunocytochemically to reveal neurons containing the neurotransmitter GABA. Three groups of neurons (groups I, II, and III neurons) were examined in terms of their distribution, density, and percentage present. Group I neurons are single-labeled with fluoro-gold and represent non-GABAergic neurons projecting to the NOT/DTN. These neurons are of the highest density in the lateral terminal nucleus (204 neurons/mm2). Their densities are also substantial in the MTNv (120 neurons/mm2), interstitial nucleus of the superior fasciculus, posterior fibers (96 neurons/mm2), and visual tegmental relay zone (93 neurons/mm2). Group II neurons are double-labeled with fluoro-gold and GABA. They form a system of GABAergic neurons projecting to the NOT/DTN, which are exceedingly dense in the MTNd (78 neurons/mm2) but are also dense in both the visual tegmental relay zone (49 neurons/mm2) and MTNv (33 neurons/mm2). Group III neurons are GABAergic neurons that do not target the NOT/DTN but must project to other brain nuclei and/or be interneurons. These are of extremely high concentration in the visual tegmental relay zone (316 neurons/mm2) and are also of substantial densities in the MTNd (77 neurons/mm2), lateral terminal nucleus (72 neurons/mm2), and MTNv (44 neurons/mm2). The MTNd has the highest percentage of GABAergic neurons projecting to the NOT/DTN (72%). GABAergic neurons also form significant percentages of the projections to the NOT/DTN from the visual tegmental relay zone (34%) and MTNv (21%). The percentage of the total GABAergic neurons that project to the NOT/DTN is the highest in the MTNd (50%) and MTNv (42%). The described GABAergic afferents to the NOT/DTN may function to process information concerned with the compensation for retinal slip.

Animals↗
PubMed1979

Cavernous hemangioma of optic chiasm, optic nerves and right optic tract. Case report and review of literature.

Diminishing right ocular visual acuity for three weeks in a 30 year old man was confirmed by examination. Bilateral scotomata and bitemporal hemiachromatopsia indicated a chiasmal lesion; reduced visual acuity and Marcus Gunn pupil of the right eye and left relative temporal hemianopia indicated asymmetric involvement. Erythrocytes in the CSF verified a suspected subarachnoid bleed; contrast-enhanced CAT scan demonstrated a suprasellar mass. A cystic, multiloculated, bluish mass distorted the right optic nerve, tract, and chiasm. A hematoma was evacuated and biopsy revealed a cavernous hemangioma of the right optic nerve. Post-operatively, visual acuity has recovered in the right eye but a left homonymous temporal hemianopia has developed.

Adult↗
PubMed1989

[Pallor of the optic papilla--an early sign of glaucoma. A clinical controlled study of optic disk pallor and papillar cupping in glaucoma simplex, ocular hypertension and normal eyes with the optic nerve head analyzer].

Double examinations of 99 eyes (34 healthy, 12 with ocular hypertension, 53 with primary open-angle glaucoma) were performed with the Optic Nerve Head Analyzer to evaluate whether an increase in disk pallor or in the cup-disk ratio (CDR) is the earlier sign of glaucoma. In eyes with primary open-angle glaucoma the CDR and the mean optic disk pallor value are significantly higher than in healthy eyes. There is no significant difference in the CDR of patients with ocular hypertension as compared to normals. However, the mean pallor value is significantly higher in eyes with ocular hypertension than in healthy eyes. Therefore, an increase in pallor may precede a significant increase in the CDR or detectable visual field defects.

Glaucoma, Open-Angle↗