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At least 19 recordsLinked to original sources
PubMed1987

The position of the crossed and uncrossed optic axons, and the non-optic axons, in the optic tract of the rat.

The position of the crossed and uncrossed optic axons, and of the non-optic axons, within the optic tract was determined in the adult hooded rat. Horseradish peroxidase histochemistry and lesion-induced degeneration of axonal profiles were independently used to study the position of the three relevant populations of axons within the optic tract. The boundaries of the optic tract are distinct at all but its caudomedial border, where it abuts the supra-optic commissures running parallel to the fibres of the optic tract. Labelling the crossed population of optic axons, or inducing their degeneration, both demonstrate a clear caudomedial border of the optic tract, although a number of optic axons stray out of the optic tract and course within the supra-optic commissures immediately caudomedial to the tract. The uncrossed optic axons are, as a population, positioned relatively deep in the optic tract, towards its dorsal border. A few occur at further ventral positions, but their density is greatly reduced there. There is also a very thin region along the dorsalmost edge of the optic tract free of uncrossed optic axons. The relative position of the uncrossed to the crossed optic axons is discussed in the context of the mammalian optic tract as a chronological map: spatial position in the tract may reflect temporal order of axonal arrival during early development. A large population of non-optic axons belonging to Gudden's commissure courses within the boundaries of the optic tract at a relatively ventral position. They are most frequent caudomedially, and are absent rostrolaterally. Hence, axons of the optic tract and Gudden's commissure are substantially intermingled in the caudomedial half of the optic tract. These non-optic axons greatly outnumber the uncrossed optic axons, and will consequently distort counts of uncrossed optic axons based on intact profiles that remain after removal of the opposite eye. However, they are still a minority in comparison to the crossed optic axons in this region.

Animals↗
PubMed1999

Optic nerve regeneration after intravitreal peripheral nerve implants: trajectories of axons regrowing through the optic chiasm into the optic tracts.

We have studied axon regeneration through the optic chiasm of adult rats 30 days after prechiasmatic intracranial optic nerve crush and serial intravitreal sciatic nerve grafting on day 0 and 14 post-lesion. The experiments comprised three groups of treated rats and three groups of controls. All treated animals received intravitreal grafts either into the left eye after both left sided (unilateral) and bilateral optic nerve transection, or into both eyes after bilateral optic nerve transection. Control eyes were all sham grafted on day 0 and 14 post-lesion, and the optic nerves either unlesioned, or crushed unilaterally or bilaterally. No regeneration through the chiasm was seen in any of the lesioned control optic nerves. In all experimental groups, large numbers of axons regenerated across the optic nerve lesions ipsilateral to the grafted eyes, traversed the short distal segment of the optic nerve and invaded the chiasm without deflection. Regeneration was correlated with the absence of the mesodermal components in the scar. In all cases, axon regrowth through the chiasm appeared to establish a major crossed and a minor uncrossed projection into both optic tracts, with some aberrant growth into the contralateral optic nerve. Axons preferentially regenerated within the degenerating trajectories from their own eye, through fragmented myelin and axonal debris, and reactive astrocytes, oligodendrocytes, microglia and macrophages. In bilaterally lesioned animals, no regeneration was detected in the optic nerve of the unimplanted eye. Although astrocytes became reactive and their processes proliferated, the architecture of their intrafascicular processes was little perturbed after optic nerve transection within either the distal optic nerve segment or the chiasm. The re-establishment of a comparatively normal pattern of passage through the chiasm by regenerating axons in the adult might therefore be organised by this relatively immutable scaffold of astrocyte processes. Binocular interactions between regenerating axons from both nerves (after bilateral optic nerve transection and intravitreal grafting), and between regenerating axons and the intact transchiasmatic projections from the unlesioned eye (after unilateral optic nerve lesions and after ipsilateral grafting) may not be important in establishing the divergent trajectories, since regenerating axons behave similarly in the presence and absence of an intact projection from the other eye.

Age Factors↗
PubMed2003

Correlation between optic disc atrophy and aetiology: anterior ischaemic optic neuropathy vs optic neuritis.

BACKGROUND: The morphologic features of swollen disc in the acute stage of optic neuritis and anterior ischaemic optic neuropathy (AION) have been extensively investigated in contrast to the morphologic features of optic disc atrophy after these events. OBJECTIVE: : A prospective study to evaluate the morphologic features of optic disc atrophy 6 months or more after optic neuritis and nonarteritic AION. PATIENTS AND METHODS: A total of 35 optic discs after nonarteritic AION (n=27) and 24 after optic neuritis (n=19) in otherwise healthy subjects have been evaluated by direct fundoscopic examination with a +90 diopters lens and optic disc photography. The average age of patients at the onset of AION was 57.8 years (range: 38-80) and at the onset of optic neuritis was 32.6 (range: 19-46). The female:male ratio was 18 : 17 in the former and 15 : 9 in the latter. The evaluated parameters included: degree of rim pallor (0 to +3), location of rim pallor, height of rim above the retina, depth and width of cup, peripapillary retinal artery to vein (A : V) ratio, and peripapillary pigment epithelial atrophy. A comparison was made also with 17 age-matched normal discs of 17 patients. Statistical significance was calculated with chi(2) and Fisher's exact test. RESULTS: Most of the discs after AION were paler (+2: 70%, +3: 26%) than after optic neuritis (normal colour: 8%, +1: 58%, P< or =0.007). Rim segmental involvement after AION was usually either superior 'altitudinal' (53%) or inferior 'altitudinal' (29%), whereas after optic neuritis, it was usually either temporal-central (papillomacular) (42%) or diffuse temporal (42%, P<0.0001). Discs had lower A : V ratio (1 : 3, 40%) after AION compared with optic neuritis (1 : 3, 8%) (P=0.007). There were no significant differences between the two groups in height of the rim, cupping, and peripapillary atrophy. CONCLUSIONS: : A combination of the degree of rim pallor, location of rim pallor, and A : V ratio may be of value in assessing the aetiology of optic disc atrophy when no previous clinical data are available and a compressive lesion has been ruled out.

Acute Disease↗
PubMed1997

Diameter of the optic nerve in idiopathic optic neuritis and in anterior ischemic optic neuropathy.

PURPOSE: There is considerable overlap in the clinical profile of patients with idiopathic optic neuritis (ON) and anterior ischemic optic neuropathy (AION). We tested the hypothesis that the retrobulbar diameter of the optic nerve may be a criterion for the differential diagnosis between ON and AION. METHODS: The diameter of the optic nerve was measured by B-scan ultrasonography with the eye in an abducted position. Only patients with a unilateral optic neuropathy were included, 16 ON patients (mean age 24 years, 5 with and 11 without disc swelling) and 9 patients with AION (mean age 72 years). As controls for the ON patients 10 young normal subjects (mean age 25 years) and as controls for the AION patients 10 elderly subjects with eye problems not related to the optic nerve (mean age 76 years) were examined. RESULTS: In the ON patients with disc swelling the diameter of the optic nerve was 5.4 +/- 0.5 mm in the affected and 3.0 +/- 0.3 mm in the unaffected side. This difference was significant (Wilcoxon-test, p = 0.043). In the ON patients without disc swelling the diameter of the optic nerve was 4.4 +/- 0.4 mm in the affected and 3.0 +/- 0.3 mm in the unaffected side. This difference was significant (Wilcoxon-test, p = 0.003). In the AION patients the diameter of the optic nerve was 3.0 +/- 0.3 mm on the affected and 2.8 +/- 0.4 mm on the unaffected side. This difference was not significant (Wilcoxon-test, p = 0.093). Comparing the optic nerves with ON and AION to those of the controls, the diameter was significantly enlarged in the nerves with ON and normal in the nerves with AION (one factor repeated ANOVA). CONCLUSION: The diameter of the optic nerve is increased in ON without disc swelling and even more so in ON with disc swelling. The enlargement is probably due to edema of the nerve itself, not the surrounding subarachnoidal space. In AION, the diameter of the optic nerve is normal. Measuring the diameter of the optic nerve by B-scan ultrasonography is particularly useful in the differential diagnosis between ON with disc swelling and AION.

Adolescent↗
PubMed1997

Does optic disc appearance distinguish ischemic optic neuropathy from optic neuritis?

OBJECTIVE: To determine whether characteristics of optic nerve swelling assist in distinguishing between optic neuritis and anterior ischemic optic neuropathy. METHOD: Optic nerve stereophotograph review by masked observers. RESULTS: Altitudinal swelling, pallor, arterial attenuation, and hemorrhage are found more commonly in anterior ischemic optic neuropathy than in optic neuritis. CONCLUSION: Optic disc appearance does help to distinguish anterior ischemic optic neuropathy from optic neuritis, although there are overlapping features.

Acute Disease↗
PubMedDate not supplied

[Revascularization decompression of the optic nerve: a new surgery of the optic nerve in progressive glaucomatous optic neuropathy].

A new operation on the optic nerve scleral canal, revascularization compression of the optic nerve, was carried out in 21 patients (21 eyes) in order to improve the visual functions and stabilize the glaucomatous process. The operation combines the advantages of decompression of the optic nerve by dissection of the posterior scleral ring with creation of an additional source of blood supply to the optic nerve from the myovascular bundle of the internal rectal muscle. Good functional effect and notable improvement of hemoperfusion of the optic nerve and retina were attained (period of observation up to 2 years). The degree of visual field extension correlated with the degree of increase in hemoperfusion values. Comparative analysis showed a higher functional efficiency of revascularization decompression of the optic nerve in comparison with optic nerve decompression, which is due to a more essential improvement of ocular hemoperfusion.

Aged↗
PubMed1997

Visual function 5 years after optic neuritis: experience of the Optic Neuritis Treatment Trial. The Optic Neuritis Study Group.

OBJECTIVE: To assess the 5-year visual course, including the incidence of recurrent optic neuritis, in 454 patients enrolled in the Optic Neuritis Treatment Trial. METHODS: Five-year follow-up vision testing, which included measures of visual acuity, contrast sensitivity, visual field, and color vision, was completed for 397 (87%) of the 454 patients. RESULTS: Visual function test results in the eyes that experienced optic neuritis at study enrollment (affected eyes) were normal or only slightly abnormal after 5 years in most patients; the results did not significantly differ by treatment group (P=.37 for visual acuity). The visual acuity in the affected eyes was 20/25 or better in 87%, 20/25 to 20/40 in 7%, 20/50 to 20/190 in 3%, and 20/200 or worse in 3%. The recurrence of optic neuritis in either eye occurred in 28% of the patients and was more frequent in patients with multiple sclerosis (P=.001) and in patients without multiple sclerosis who were in the prednisone treatment group (P=.004). Most eyes with a recurrence retained normal or almost normal visual function. CONCLUSIONS: Most patients retained good to excellent vision in the 5 years following an attack of optic neuritis, even if the optic neuritis recurred. Recurrences were more frequent in patients with multiple sclerosis and in those treated with oral prednisone alone. The completion of the 5-year follow-up by the Optic Neuritis Treatment Trial cohort has not altered our management recommendations based on the results we reported earlier.

Administration, Oral↗
PubMed2002

Diffractive optical elements based on Fourier optical techniques: a new class of optics for extreme ultraviolet and soft x-ray wavelengths.

A diffractive optical element, based on Fourier optics techniques, for use in extreme ultraviolet/soft x-ray experiments has been fabricated and demonstrated. This diffractive optical element, when illuminated by a uniform plane wave, will produce two symmetric off-axis first-order foci suitable for interferometric experiments. The efficiency of this optical element and its use in direct interferometric determination of optical constants are also discussed. Its use in direct interferometric determination of optical constants is also referenced. Its use opens a new era in the use of sophisticated optical techniques at short wavelengths.

Journal Article↗
PubMed1993

Baseline visual field profile of optic neuritis. The experience of the optic neuritis treatment trial. Optic Neuritis Study Group.

The purpose of the present study was to determine the baseline visual field characteristics in 448 patients with acute optic neuritis who were entered into the Optic Neuritis Treatment Trial. The severity and pattern of visual field loss in both the affected and fellow eyes were classified. For affected eyes, diffuse visual field loss was present in 48.2% of eyes, central or centrocecal scotoma was present in 8.3% of eyes, altitudinal or other nerve-fiber bundle-type defects were present in 20.1% of eyes, and a variety of other defects were present in 23.4% of eyes. Visual field involvement was present in the fellow eye at baseline in 308 (68.8%) of the 448 patients. Evidence of a chiasmal or retrochiasmal visual field defect was present in 2.9% of the patients. Since a wide variety of visual field defects can occur with an acute attack of optic neuritis, the pattern of visual field loss is of limited utility in distinguishing optic neuritis from ischemic optic neuropathy and other optic nerve disorders. Asymptomatic visual field defects in the fellow eye are common.

Acute Disease↗
PubMed1989

Impulse blockade by intraocular tetrodotoxin during optic regeneration in goldfish: HRP-EM evidence that the formation of normal numbers of optic synapses and the elimination of exuberant optic fibers is activity independent.

Optic fibers and synapses labeled with HRP were counted in the primary optic innervation layer of tectum after continuously blocking visual impulse activity with TTX during regeneration. Normal numbers of optic and nonoptic fibers and synapses were found at both 30 and 60 d, and key ultrastructural features of optic afferents such as fiber fasciculation, myelination, terminal clustering, synaptogenesis onto different classes of postsynaptic targets and general morphology were not notably affected by impulse blockade. These findings indicate that during regeneration the normal proliferation and elimination of optic fibers and the formation of normal numbers of optic synapses are not regulated by activity and are consistent with a pattern formation role for impulse activity rather than a trophic one.

Animals↗
PubMed2004

Optical characteristics of a refractive optical attenuator with respect to the wedge angles of a silicon optical leaker.

We design, fabricate, and characterize the micromachined refractive variable optical attenuator (VOA) with a wedge-shaped silicon optical leaker (SOL). The vertical structures of the VOA device can be simply fabricated by deep reactive ion etching with no sidewall metallization, and the 8 degrees angled fibers are employed for a high return loss even in air-ambient conditions. The SOL successively transmits and refracts part of the incident light far outside the acceptance angle of the output fiber, showing an effective optical attenuation. The fabricated VOA gives high optical performances, such as a response time of 6 ms, a return loss of 39 dB, an insertion loss of 0.6 dB, an attenuation range of 43 dB, and a polarization-dependent loss (PDL) of a 10% attenuation level, including a wavelength-dependent loss. The optical characteristics of the VOA are also theoretically investigated with respect to the wedge angles of the SOL. The experimental characteristics are in good agreement with the theoretical values calculated, considering light scattered from the endface of an optical fiber and sidewall of the SOL. The PDL estimation was confirmed especially to sufficiently explain the fundamental characteristic of the PDL for the refractive VOA.

Journal Article↗
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↗
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↗