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PubMed2004

Reproducibility of nerve fiber thickness, macular thickness, and optic nerve head measurements using StratusOCT.

PURPOSE: The measurement reproducibility of the third generation of commercial optical coherence tomography, OCT-3 (StratusOCT, software ver. A2, Carl Zeiss Meditec Inc., Dublin, CA) was investigated. The nerve fiber layer (NFL) thickness, macula thickness map, and optic nerve head (ONH) parameters in normal eyes were studied. METHODS: Ten normal subjects were imaged six times (three before and three after dilation) per day, and the series was repeated on three different days. The order of the scans before pupil dilation was randomized in each of the 3 days of scanning. After pupil dilation, the scans were also randomized in each of the 3 days of scanning. Each series was performed separately for standard-density (128 A-scans per macular and ONH image and 256 A-scans per NFL image) and high-density (512 A-scans per image for all three scan types) scanning. RESULTS: The mean macular thickness was 235 +/- 9.8 micro m. A-scan density (or image acquisition speed) had a statistically significant effect (P < 0.05) on the reproducibility of the mean macular thickness, macular volume, and a few sectors of the macular map. No significant dilation effect was found for any of the macular parameters. The best intraclass correlation coefficient (ICC; 94%) for macular scans was found for dilated high-density scanning, with an intervisit SD of 2.4 micro m and an intravisit SD of 2.2 micro m. The mean NFL thickness for standard scanning was 98 +/- 9 micro m. NFL reproducibility showed mixed results and had interactions between scan density and dilation for some parameters. For most of the NFL parameters, reproducibility was better with dilated standard-density scanning. The mean NFL thickness ICC for dilated standard scanning was 79%, with an intervisit SD of 2.5 micro m and an intravisit SD of 1.6 micro m. For the ONH analysis, the reproducibility was better for dilated standard-density scanning for almost all the parameters, except for disc area, horizontal integrated rim volume, and vertical integrated rim area, which were better before dilation. The best reproducibility was found for cup-to-disc ratio (ICC = 97%, with intervisit SD of 0.04 micro m and intravisit SD of 0.02 micro m). CONCLUSIONS: StratusOCT demonstrated reproducible measurements of NFL thickness, macular thickness, and optic nerve head parameters. The best reproducibility was found for dilated standard scanning for NFL and ONH parameters and for dilated high-density scanning for macular parameters.

Adult↗
PubMed2003

Glial cells in the chicken optic tectum.

We mapped the distribution of the three neuroglial cells, oligodendrocytes, astrocytes and microglia, in the chicken optic tectum using their specific markers, transferrin binding protein (TfBP), glial fibrillary acidic protein (GFAP), and Ricinus communis agglutinin-1 (RCA-1), respectively. Neuroglial cells showed distinct distribution according to their cell types. While the astrocytes were mainly found in the stratum opticum (SO), stratum album centrale (SAC) and stratum fibrosum periventriculare (SFP), with their processes extending throughout the entire optic tectum region, the oligodendrocytes were mainly scattered in the SO, stratum griseum centrale (SGC) and SAC. In the case of the microglia, ramified cells were found in nearly all the layers, with the majority being present in the SAC. This is the first report demonstrating the distribution of glial cells in the chicken optic tectum, and these findings may present a basis for further study.

Animals↗
PubMed1982

Retinotectal map formation in dually innervated tecta: a regeneration study in Xenopus with one compound eye following bilateral optic nerve section.

Retinotectal map formation was studied during regeneration in young adult Xenopus. Right compound double-temporal eyes (TT) were formed in tailbud stage embryos by the fusion of two temporal halves of the eye blastema in the same orbit. In other animals right compound double-nasal eyes (NN) were prepared. In both combinations the left eye was kept intact. After metamorphosis the right and left optic nerves were sectioned to induce optic fiber regeneration from each eye to both tecta. The patterns of retinotectal projections from the compound and normal eyes were studied from 37 to 364 days after optic nerve section, using electrophysiological recording of the visuotectal projections and 3H-proline autoradiographic assay from one of the two eyes. The left normal eyes projected in a retinotopic fashion, across the entire extent of the right and left dually innervated tecta. In contrast, the right compound eye projections were confined to the rostrolateral or to the caudomedial part of the right and left tecta and TT and NN animals, respectively. These tectal areas corresponded to the termination of temporal and nasal hemiretinal fibers of the normal eye. Discontinuous, interdigitating projection patterns from the right and left eyes were found in parts of the tecta where the compound and the normal eye projections overlapped. These results indicate that the normal optic fiber projections caused the originally expanded compound eye projections to be restricted to the corresponding part of the dually innervated tecta. It is suggested that the orderliness and the extent of the retinotectal map are established by the competition and interaction of optic fibers based on stable positional programming of the retinal ganglion cells.

Animals↗
PubMedDate not supplied

[The area of the optically activated zones of cat area 17 under stimulation with grids of different orientation].

In acute experiments with 9 anesthetized and immobilized cats, the relative tangential square of the activated cortical columns in area 17 was mapped by the intrinsic optical signal under stimulation with grids of different orientation. We examined the "oblique effect", i.e. the greater representation of neurons tuned to the vertical and horizontal orientations vs. oblique orientations in the primary visual cortex. The square of the activated parts of the cortex was estimated under different threshold criteria (80, 60 and 40% of the maximum). The "oblique effect" was not observed in our study: the areas of activation of the cortical columns did not differ statistically for two basic vs. oblique orientations. Reasons for the difference between the results of electrophysiological and optical mapping are suggested and possible contributions of the experimental protocol (anesthesia) and individual visual experience in different animals' samples to the origin of these differences are discussed.

Animals↗
PubMedDate not supplied

Arrangement of optical axes and spatial resolution in the compound eye of the female blowfly Calliphora.

We determined the optical axes of ommatidia in the wild-type female blowfly Calliphora by inspecting the deep pseudopupil in large parts of the compound eye. The resulting map of optical axes allowed us to evaluate the spatial resolution in different parts of the eye in terms of interommatidial angles as well as the density of optical axes, and to estimate the orientation of ommatidial rows along the hexagonal eye lattice. The optical axes are not homogeneously distributed over the eye. In the frontal visual field the spatial resolution is about two times higher than in its lateral part and about three times higher as compared to the eye's dorsal pole region. The orientation of the ommatidial rows along the eye lattice is not the same for different regions of the eye but changes in a characteristic way. The inter-individual variability in the orientation of the ommatidial rows is estimated to be smaller than 8 degrees . The characteristic arrangement of the ommatidial lattice is discussed as an adaptation for efficient evaluation of optic flow as induced during self-motions of the animal.

Animals↗
PubMed2003

Mapping posterior vitreous detachment by optical coherence tomography in eyes with idiopathic macular hole.

PURPOSE: To determine the relationship between posterior vitreous detachment and idiopathic macular hole. DESIGN: Observational case series. METHODS: In a prospective study, the posterior hyaloid face was scanned from the posterior pole to the far periphery by optical coherence tomography in 25 eyes (22 patients) with an idiopathic macular hole (stage 1 = 1, stage 2 = 7, stage 3 = 10, and stage 4 = 7), and a map of the posterior vitreous detachment was constructed. RESULTS: One eye with a stage 1 macular hole had a posterior vitreous detachment confined to the vascular arcade, but attached to the fovea. In all seven eyes at stage 2, the detached posterior hyaloid enlarged upward beyond the superior vascular arcade, but stopped at the margin of inferior vascular arcade. In two cases, the posterior vitreous detachment also extended temporally and superonasally. In all cases, the vitreous face remained attached to the fovea. Six of the 10 eyes at stage 3 had larger partial posterior vitreous detachment that extended not only upward, but also beyond the inferior vascular arcade, while in the other four eyes, the size and position of the posterior vitreous detachment was similar to stage 2 macular holes. However, unlike stage 2, the posterior vitreous detachment included the fovea in all eyes. All seven eyes with a stage 4 macular hole had complete posterior vitreous detachment that extended to the far periphery in all directions. CONCLUSION: There is a close correlation between the stage of the macular hole and the degree of posterior vitreous detachment. This close correlation suggests that progression of idiopathic macular hole is related to enlargement of the posterior vitreous detachment.

Aged↗
PubMed2004

A direct method to measure the power of the central cornea after myopic laser in situ keratomileusis.

OBJECTIVE: To measure the corneal power after myopic laser in situ keratomileusis (LASIK). METHODS: Six central areas in 6 corneal power maps were studied using the Orbscan II statistical analysis device in 26 eyes that underwent myopic LASIK. Refractive and corneal power changes were compared. Factors related to wrong corneal power measurement were evaluated. MAIN OUTCOME MEASURES: Cycloplegic refraction, refractive change at the corneal plane, and Orbscan II corneal power maps. RESULTS: Preoperatively, only posterior-mean power (P<<.001) and anterior-posterior power ratio (P<<.001) varied according to the size of the analyzed area. Postoperatively, total-optical (P =.03), keratometric-mean (P =.04), total-mean (P<.001), anterior-mean (P =.03), and posterior-mean (P<<.001) powers; and anterior-posterior power ratio (P<<.001) varied according to the area. Postoperatively, the difference between keratometric-mean and total-mean powers became larger (P<.001), and the anterior-posterior power ratio was reduced (P<<.001). A posterior-mean power change occurred (P =.04). Refractive change after myopic LASIK was best estimated by 2-mm total-mean power (mean +/- SD difference, 0.07 +/- 0.62 diopters [D]; P =.55) and 4-mm total-optical power (mean +/- SD difference, -0.08 +/- 0.53 D; P =.37). CONCLUSIONS: Total corneal power is more positive and refractive change is underestimated when deduced from the anterior surface radius and keratometric refractive index. The anterior-posterior power ratio is not a fixed value. The best area to estimate the refractive change depends on the method used to obtain the power in diopters. Refractive change tended to be underestimated in larger areas and higher preoperative myopia. Orbscan II total-mean and total-optical power maps accurately assess the corneal power after myopic LASIK independent of preoperative data or correcting factors, and should improve intraocular lens calculation.

Adult↗
PubMed1999

Density structure of the Sgr B2 molecular cloud probed by low-J lines of CS.

We have observed the CS (2-1) and (3-2), and 13CS (2-1) transitions toward the Galactic Center molecular cloud Sgr B2 which consists of several clumps with different chemical properties. We have newly identified a cloud at 30 km s-1 from a CS (2-1) optical depth map. This cloud lies 1.5' South from the Sgr B2 (M) position and has a diameter of approximately 2.5 pc and a total column density of 7 x 10(23) cm-2 assuming optically thin emission of the 13CS (2-1) line. Towards the 2'N Cloud no evidence for a density enhancement is found, which suggests that the strong emission from HNCO and HCO+2 is due to chemical effects. The main isotopic CS lines show broad wing components similar to previous studies, but we find rotational temperatures Trot(CS) < 10 K at this region.

Astronomy↗
PubMed1982

Auditory and visual maps of space in the optic tectum of the owl.

The receptive field properties and functional organization of visual and auditory responses were studied in the optic tectum of the barn owl (Tyto alba). Most units throughout the depth of the tectum responded to both visual and auditory stimuli. The entire visual field of each eye was represented topographically in the contralateral tectum. In the portion of the tectal map representing the zone of binocular vision, 50% of the superficial layer units and 100% of the deep; layer units were driven binocularly. The representation of the frontal binocular region of space was greatly expanded in the map; the average magnification factor was 3 times greater for the frontal binocular zone than for the monocular zone. The responses of the superficial and deep tectal units to auditory stimuli were space specific; they responded only when a sound source was located in a particular region of space, or receptive field, regardless of the intensity or type of sound used. Most auditory receptive fields contained a distinct "best area" where a sound source was most effective in driving the unit. Auditory space, as defined by receptive fields and best areas, was represented topographically in the tectum. The auditory and visual maps of space had the same orientations, positions, magnification factors, and termination coordinates at the anterior and dorsal edges of the tectum. Yet the maps lost their registry near the posterior and ventral margins where the most peripheral regions of space were represented. These characteristics suggest that the spatiotopic organization in the tectum is a compromise between a tendency for the space representations of different modalities to align and for the representation of each modality to fill the entire tectum.

Acoustic Stimulation↗
PubMed1976

Prenatal development of central optic pathways in albino rats.

The development of the central optic projections in albino rat fetuses has been studied using light and electron microscopic degeneration techniques and the horseradish peroxidase method for demonstrating axonal projections of neurons. The first optic axons to reach the region of the optic chiasm arrive at day 15. By day 16, a substantial optic chiasm is seen and the optic tract can be traced into the epithalamus, having first passed through the ventral lateral geniculate nucleus and a thin lamina of cells which is thought to correspond to part of the future dorsal geniculate nucleus. A growth rate of 80-100 mum per hour is estimated for the fastest growing axons. By day 16-1/3 the first axons have entered the anterior border of the superior colliculus and in the next day have grown across the entire rostrocaudal extent with the exception of the medial and lateral edges. The optic axons are recognized at day 17 as bundles lying just below the surface, but in older animals they come to lie deeper, as the whole layer of optic innervation broadens. The first synapses to be formed in the superior colliculus (some of them of optic origin) appear on day 17. Subsequently, there is a gradual increase in the number of contacts, the great majority being formed by optic axons. Compared with previous studies on Xenopus and chick, one of the most striking features of the development of the central visual connections in the rat is the relatively long time before the first optic axons reach the brain and the speed with which they innervate the central structures once they have arrived.

Animals↗
PubMed2001

A high-density transcript map of the human dominant optic atrophy OPA1 gene locus and re-evaluation of evidence for a founder haplotype.

Dominant optic atrophy (DOA, gene OPA1) is the commonest form of inherited optic atrophy. Linkage studies have shown that a locus for this disease lies in a 1.4-cM region at chromosome 3q28-->q29 and have suggested a founder haplotype for as many as 95% of the linked families. To aid the identification of candidate genes for this disease, we have constructed a Bacterial Artificial Chromosome (BAC) contig covering approximately 3.3 Mb and encompassing the OPA1 critical region (flanking markers D3S3669 and D3S3562). This physical map corrects errors in the marker order reported in the literature, allowing the OPA1 critical region to be precisely defined. A reassessment of the founder effect in the light of the revised marker order suggests that it may not be as significant as had previously been suggested. A high-density transcript map was created by precisely mapping genes and expressed sequence tags (ESTs) from GeneMap'99, that have been loosely assigned to the region by radiation hybrid mapping. One known gene (KIAA0567 protein) and 15 ESTs were found to lie within the minimal disease region. Analysis of the sequence data already available from within the OPA1 critical region allowed the identification and mapping of a further 31 ESTs. The work presented in this study provides the basis for the characterisation of candidate genes and the ultimate identification of the gene mutated in DOA.

Chromosomes, Artificial, Bacterial↗
PubMed2001

Calculating direction maps from intrinsic signals revealed by optical imaging.

Previous optical imaging studies used the vector-summation (VS) method for calculating direction and orientation preference maps. However, for direction maps it often resulted in direction vectors which showed a steep angle to that of orientation vectors violating the 'aperture rule'. The present report provides a simple procedure for calculating direction preference maps using the 'electro- physiologist's ear' approach. This approach takes into account the strongest directional response component (vector-maximum, VM) in each pixel of the optical image, reminiscent of how electro- physiologists determine direction preference by audio-monitoring of the firing rate of neurons. The major advantage of this method is that the orthogonal relationship between orientation and direction preference vectors is preserved and that for most image pixels direction preference can be faithfully described by a single vector parameter. Here we used the VM method for calculating direction and the VS method for calculating orientation preference maps and quantified their spatial relationship. The results showed that, typically, an iso-orientation domain contained a pair of patches that preferred opposite directions orthogonal to the orientation. Rate-of-change maps for direction revealed that virtually all direction discontinuity lines linked orientation centres. Close to orientation centres, direction discontinuity lines ran chiefly parallel with iso-orientation lines, whereas more remotely they had either parallel or perpendicular courses.

Animals↗
PubMed1991

Optical methods can be utilized to map the location and activity of putative motor neurons and interneurons during rhythmic patterns of activity in the buccal ganglion of Aplysia.

We sought to develop a map of the locations of neurons that are active during patterned activity in the buccal ganglion of Aplysia using optical techniques. Staining ganglia with a voltage-sensitive absorbance dye (JPW 1124) did not prevent them from generating patterned activity similar to that observed before staining, in response to shock of the esophageal nerve. Absorbance changes were monitored with a 124-element photodiode array, while extracellular electrodes monitored activity of the 6 buccal nerves. Optical and extracellular spikes were grouped with the aid of a template matching program; a total of 120 distinct units were detected in one 15 s recording. Optical signals (83 units) were found in the region of the ganglion containing mainly large neurons. Of these, 13 were detected on both optical and extracellular electrode recordings, suggesting that they might be motor neurons, while 25 of the optically detected neurons appeared not to be correlated with extracellular activity, suggesting that they might be interneurons. It was not possible to determine whether the remaining 45 optically identified units did or did not have correlated nerve activity. The ganglionic locations of putative motor neurons corresponded to the locations of large neurons identified by backfilling nerves of other buccal ganglia, and were consistent with the locations of putative motor neurons found in two other ganglia studied using optical methods. Thus, optical methods have generated a map of the locations and activity patterns of putative motor neurons and interneurons in the buccal ganglion that may be involved in the generation of rhythmic patterns.

Animals↗
PubMed2004

Visual stimulation, 1H MR spectroscopy and fMRI of the human visual pathways.

The purpose was to assess changes in lactate content and other brain metabolites under visual stimulation in optical chiasm, optic radiations and occipital cortex using multiple voxel MR spectroscopy (MRS). 1H chemical shift imaging (CSI) examinations of transverse planes centered to include the above structures were performed in four subjects at an echo time of 135 ms. Functional MRI (fMRI) was used to confirm the presence of activity in the visual cortex during the visual stimulation. Spectral maps of optical chiasm were of poor quality due to field disturbances caused by nearby large blood vessels and/or eye movements. The optic radiations and the occipital lobe did not show any significant MR spectral change upon visual stimulation, i.e., the peak areas of inositol, choline, creatine, glutamate and N-acetylaspartate were not affected. Reproducible lactate signals were not observed. fMRI confirmed the presence of strong activations in stimulated visual cortex. Prolonged visual stimulation did not cause significant changes in MR spectra. Any signal observed near the 1.33 ppm resonance frequency of the lactate methyl-group was artifactual, originating from lipid signals from outside the volume of interest (VOI). Previous claims about changes in lactate levels in the visual cortex upon visual stimulation may have been based on such erroneous observations.

Adult↗
PubMed1997

Registration of neural maps through value-dependent learning: modeling the alignment of auditory and visual maps in the barn owl's optic tectum.

In the optic tectum (OT) of the barn owl, visual and auditory maps of space are found in close alignment with each other. Experiments in which such alignment has been disrupted have shown a considerable degree of plasticity in the auditory map. The external nucleus of the inferior colliculus (ICx), an auditory center that projects massively to the tectum, is the main site of plasticity; however, it is unclear by what mechanisms the alignment between the auditory map in the ICx and the visual map in the tectum is established and maintained. In this paper, we propose that such map alignment occurs through a process of value-dependent learning. According to this paradigm, value systems, identifiable with neuromodulatory systems having diffuse projections, respond to innate or acquired salient cues and modulate changes in synaptic efficacy in many brain regions. To test the self-consistency of this proposal, we have developed a computer model of the principal neural structures involved in the process of auditory localization in the barn owl. This is complemented by simulations of aspects of the barn owl phenotype and of the experimental environment. In the model, a value system is activated whenever the owl carries out a foveation toward an auditory stimulus. A term representing the diffuse release of a neuromodulator interacts with local pre- and postsynaptic events to determine synaptic changes in the ICx. Through large-scale simulations, we have replicated a number of experimental observations on the development of spatial alignment between the auditory and visual maps during normal visual experience, after the retinal image is shifted through prismatic goggles, and after the reestablishment of normal visual input. The results suggest that value-dependent learning is sufficient to account for the registration of auditory and visual maps of space in the OT of the barn owl, and they lead to a number of experimental predictions.

Animals↗
PubMed1994

Future directions for functional mapping.

The intracarotid amobarbital procedure and direct cortical stimulation are commonly used techniques for functional mapping in candidates for epilepsy surgery. The role of these two procedures has been challenged recently. Emerging technologies recently applied to functional mapping include optical imaging, functional positron emission tomography studies, transcranial magnetic stimulation, magnetoencephalography, and fast magnetic resonance imaging. Studies have used these new technologies and the potential for these procedures to replace the established but more invasive techniques is being considered.

Amobarbital↗
PubMed1996

Optical image reconstruction using DC data: simulations and experiments.

In this paper, we explore optical image formation using a diffusion approximation of light propagation in tissue which is modelled with a finite-element method for optically heterogeneous media. We demonstrate successful image reconstruction based on absolute experimental DC data obtained with a continuous wave 633 nm He-Ne laser system and a 751 nm diode laser system in laboratory phantoms having two optically distinct regions. The experimental systems used exploit a tomographic type of data collection scheme that provides information from which a spatially variable optical property map is deduced. Reconstruction of scattering coefficient only and simultaneous reconstruction of both scattering and absorption profiles in tissue-like phantoms are obtained from measured and simulated data. Images with different contrast levels between the heterogeneity and the background are also reported and the results show that although it is possible to obtain qualitative visual information on the location and size of a heterogeneity, it may not be possible to quantitatively resolve contrast levels or optical properties using reconstructions from DC data only. Sensitivity of image reconstruction to noise in the measurement data is investigated through simulations. The application of boundary constraints has also been addressed.

Absorption↗