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PubMed1994

Conjugated deferoxamine reduces blood-brain barrier disruption in experimental optic neuritis.

The purpose of this paper was to investigate the role of deferoxamine (DFO) scavenging of hydroxyl radical (.OH) on disruption of the blood-brain barrier (BBB) and demyelination in experimental optic neuritis. Eighteen strain-13 guinea pigs were sensitized for experimental allergic encephalomyelitis. Nine animals received 100 mg/kg of hydroxyethyl starch-conjugated (HES) DFO by daily intraperitoneal injection commencing the day of antigenic sensitization. Nine paired litter mates received daily IP injections of HES. Serial fat-suppressed magnetic resonance imaging of the optic nerves was obtained with a T2 weighting (T2w) to evaluate demyelination and after intravascular administration of Gd-DTPA to evaluate BBB disruption. The intensity of Gd-DTPA enhancement and T2w signal of the optic nerves was quantitated 3, 7, 10 and 14 days after antigenic sensitization. Animals were then sacrificed and the optic nerves processed for light and transmission electron microscopy with ultracytochemical localization of endogenous hydrogen peroxide (H2O2) and immunogold colocalization of extravasated serum albumin. The area of the optic nerve head, intensity of toluidine blue staining, and the cellular infiltrate were digitized and quantitated. Administration of HES-DFO significantly reduced the intensity of Gd-DTPA enhancement in the optic nerves of HES-DFO-treated animals compared to paired control HES animals (p = 0.0236), with the mean difference between control and treated animals of 19.39. The difference in T2w signal was not significant (p = 0.39), with a mean difference between control and treated animals of -5.51. The intensity of toluidine blue staining of optic nerve specimens was slightly less with HES-DFO compared to untreated animals (mean pair difference 2.48), and the inflammatory infiltrate was reduced with HES-DFO compared to untreated animals (mean pair difference = 61.57); these differences were not statistically significant. In the optic nerve specimens of both groups cerium perhydroxide-derived H2O2 reaction product was evident in a predominantly perivascular and perineural distribution. Immunogold-labeled serum albumin showed extravasation at foci of perivascular inflammation in both the presence and absence of H2O2-derived reaction product. Conjugated DFO reduces disruption of the BBB, as measured by Gd-DTPA enhancement, suggesting the .OH radical generated from perivascular H2O2 may play a role in alterations of vascular permeability in experimental optic neuritis.

Animals↗
PubMed1996

[Optic nerve diseases in children].

The optic nerve is a part of the white matter in the central nervous system and can easily be observed with a funduscope. Neuro-ophthalmologic studies of the optic nerve is useful in monitoring disorders in the central nervous system. In this paper we presented four cases of optic nerve diseases and discussed them from the standpoint of neuro-ophthalmology. Case 1, a 9-year-old girl, had left retrobulbar optic neuritis and right papillitis which occurred one year after the onset of left optic neuritis. She was treated with a three day course of methylprednisolone (500 mg). Her left optic disc became atrophic, but her right optic disc became normal. Her visual acuity recovered to 1.0 in each eye. Relative afferent pupillary defect was seen in her left eye. Steroid therapy for optic neuritis and pupillary light reaction were discussed. Case 2 was a 7-year-old girl with teratoma in the chiasmal region, and case 3 was a 10-year-old boy with craniopharyngioma. Visual field changes caused by tumors in the chiasmal region were discussed. Case 4 was a 7-year-old boy with right optic atrophy and left papilledema, an example of Foster Kennedy syndrome. The effects of papilledema on visual function was discussed.

Child↗
PubMed1975

An electron microscope study of the retino-receptive layers of the pigeon optic tectum.

The fine structure of the superficial layer of the optic tectum of the pigeon, Columba livia, has been examined both in normal animals and after unilateral eye removal. Optic afferent terminals distributed throughout sublaminae IIa-f, are principally concentrated at three depths in the retinoreceptive zone. At first, degeneration of optic afferent terminals occurs as swelling of synaptic vesicles and accumulation of neurofilaments and later as dense degeneration. There appear to be several classes of optic afferent terminals in the retino-receptive zone, as would be expected from most previous studies of the avian tectum. The non-optic components of the neuropil, which include glomerular and pleomorphic vesicle terminals, and the synaptic interrelationships between optic and non-optic components are described. Optic afferent terminals mainly make synaptic contact with the branches of radial dendrites but also, in sublaminae IIb and IIc, with the dendrites of non-radial cells. In sublamina IIc afferent terminals synapse onto the horizontal presynaptic dendrites of spindle cells and triplet synaptic arrays including optic afferent terminals, horizontal dendrites and radial dendrite profiles and radial dendrite profiles are found. This optic projection to non-radial elements in IIb c, is discussed in relation to light microscope and electrophysiological studies.

Animals↗
PubMed1987

Retinopretectal and accessory optic projections of normal mice and the OKN-defective mutant mice beige, beige-J, and pearl.

Retinal projections to the pretectal and terminal accessory optic nuclei were studied in normal wild-type mice and mutant mice with abnormal optokinetic nystagmus (OKN, Mangini, Vanable, Williams, and Pinto: J. Comp. Neurol. 241:191-209, '85). The mutants used were pearl, which exhibits an inverted OKN in response to stimulation of only the temporal retina, and beige and beige-J, which show inverted OKN in response to stimulation of only the temporal retina and, in addition, exhibit eye movements with a vertical component in response to horizontally moving, full-field stimuli. These projections were studied following intraocular injections of 3H-proline or horseradish peroxidase (HRP) with, respectively, light microscopic autoradiography or HRP histochemistry. In wild-type mice, strong contralateral retinal projections covered the entire nucleus of the optic tract, the anterior and posterior divisions of the olivary pretectal nucleus, and the posterior pretectal nucleus. Similar heavy contralateral projections were distributed over the dorsal and medial terminal nuclei of the accessory optic system. Also, terminals sparsely covered the entire neuropil of the contralateral lateral terminal nucleus in some but not all wild-type mice. The most prominent accessory optic input was to the medial terminal nucleus and was provided by the inferior fasciculus of the accessory optic tract. A typical mammalian superior fasciculus of the accessory optic system with anterior, middle, and posterior components was present. Ipsilateral label was found in anterior and posterior olivary pretectal nuclei in all of the wild-type animals, but was found inconsistently in the ipsilateral terminal accessory optic nuclei. The pattern of contralateral retinal projection to the nucleus of the optic tract and posterior pretectal nucleus in mutants was indistinguishable from that seen in the normal wild-type mice. However, retinal inputs to the ipsilateral anterior and posterior olivary pretectal nuclei were significantly reduced in pearl mutants and were exceedingly sparse in the beige and beige-J mutant mice, while the contralateral inputs to these nuclei were increased in a complementary fashion in the mutants. The labeling of the accessory optic input to the contralateral dorsal terminal nucleus appeared to be substantially reduced in all of the mutant mice. The size of the principal accessory optic fascicle, the inferior fasciculus, was significantly smaller in beige, beige-J, and pearl mice; this reduction was greater in the beige and beige-J than in the pearl mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

Magneto-optics of Ferritin.

Measurements of Rayleigh light scattering, nonlinear light scattering in DC magnetic fields, and the Cotton-Mouton effect were carried out for 15 mM NaCl and water solutions of ferritin at room temperature. The spherical geometry of the molecule implies that it is optically isotropic. Such a macromolecule should not manifest magnetic anisotropy; however, in solution it shows induced magnetic birefringence (Cotton-Mouton effect) and changes in the intensity of the scattered light components. The analysis of the obtained results indicates the deformation of linear optical polarizability induced in the ferritin by a magnetic field as the main source of the magneto-optical phenomena observed. Light scattering and the CM effects theoretically depend on the linear magneto-optical polarizability, chi, and the nonlinear magneto-optical polarizability, eta. Using the theory describing the phenomena as well as the experimental data, the values of the anisotropy of linear magneto-optical polarizability components, chi(parallel) - chi(perpendicular) = -(1.3 +/- 0.7) x 10(-22) [cm3] (in SI units chi(parallel) - chi(perpendicular) = -(2.0 +/- 1.2) x 10(-33) [m3]), the linear optical polarizability, alpha = (alpha(parallel) + 2alpha(perpendicular))/3 = (3.9 +/- 1.0) x 10(-20) [cm3] (in SI units alpha = (3.52 +/- 0.09)x10(-4) [Cm2 V(-1)]), and its anisotropy, kappa(alpha) = (alpha(parallel) - alpha(perpendicular))/3alpha = -(0.06+/-0.03), nonlinear magneto-optical polarizability, eta = (eta(parallel) + 2eta(perpendicular))/3 = -(4.7 +/- 0.9) x 10(-30) [cm3 Oe(-2)] (in SI units eta = -(6.7 +/- 1.3) x 10(-18) [Cm4 V(-1) A(-2)]) and its anisotropy, kappa(eta) = (eta[parallel) - eta(perpendicular))/3eta = -(0.15 +/- 0.10), were deduced. Here alpha(parallel), eta(parallel), alpha(perpendicular), eta(perpendicular) are the optical and magneto-optical polarizability components along the parallel and the perpendicular axes of the axially symmetric molecule, respectively.

Animals↗
PubMed1999

Use of intrinsic optical signals to monitor physiological changes in brain tissue slices.

Optical imaging techniques have the potential to bring a combination of high spatial and temporal resolution to studies of brain function. Many optical techniques require the addition of a dye or fluorescent marker to the tissue, and such methods have proven extremely valuable. It is also known that the intrinsic optical properties of neural tissue are affected by certain physiological changes and that these intrinsic optical signals can provide information not available by other means. Most authors attribute the intrinsic optical change to alterations in cell volume and concomitant change in the concentration of the cytosol. In this article we review the literature on intrinsic optical signals, covering both the mechanisms of the optical change and its use in various branches of neurophysiology. We also discuss technical aspects of the technique as used with hippocampal slices, including illumination methods, cameras, experimental methods, and data collection and analysis procedures. Finally we present data from investigations in which we used intrinsic optical signals in hippocampal slices to study the extent of spread of synaptic activation, propagation of spreading depression, extent and severity of the response to hypoxia, and tissue response to osmotic challenges. We conclude that (1) at least two processes generate intrinsic optical signals in hippocampal slices, one of which causes light scattering to change inversely with cell volume and is related to dilution of the cytoplasm, while the other, opposite in sign, may be due to mitochondrial swelling; and (2) the intrinsic optical signal can be a useful tool for spatial mapping of relatively slow events, but is not suitable for study of fast physiological processes.

Animals↗
PubMed1995

Optical coherence tomography of central serous chorioretinopathy.

PURPOSE: To assess the potential of a new imaging technique, optical coherence tomography, for the diagnosis and monitoring of central serous chorioretinopathy. Optical coherence tomography is a novel noninvasive, noncontact imaging modality that produces high longitudinal resolution, cross-sectional tomographs of ocular tissue. METHODS: Optical coherence tomography is analogous to ultrasound, except that it uses light rather than sound to obtain higher image resolution in the retina. Cross-sectional tomographs of optical reflectivity within the retina are produced with longitudinal resolution of 10 microns. Optical coherence tomography was used to examine 16 patients at a referral eye center whose initial examination disclosed the clinical diagnosis of central serous chorioretinopathy. The optical coherence tomography results were correlated with slit-lamp biomicroscopy, fundus photography, and fluorescein angiography. RESULTS: The cross-sectional view produced by optical coherence tomography was effective in objectively quantifying the amount of serous retinal detachment in the disease. Optical coherence tomography disclosed detachments that were undetected by slit-lamp biomicroscopy. Longitudinal measurements with optical coherence tomography were successfully able to track the resolution of subretinal fluid accumulation. CONCLUSION: Optical coherence tomography is potentially useful as a new, noninvasive diagnostic technique for quantitative examination of patients with central serous chorioretinopathy and objectively monitoring the clinical course of the serous retinal detachment in this disease.

Adult↗
PubMed1993

Metastatic prostate cancer to the optic canal.

PURPOSE: Optic neuropathies represent a common cause of blindness among patients with cancer. The authors present the clinical and imaging findings and discuss the management of optic nerve involvement from metastatic prostate cancer to the optic canal. METHODS: Five patients with advanced metastatic prostate cancer had visual loss. Neuro-ophthalmologic examination and pre- and post-gadolinium orbital and brain magnetic resonance imaging (MRI) were performed. Compressive optic neuropathy secondary to extensive optic canal involvement was demonstrated in all of the patients. Neuropathologic examination was accomplished in two cases. A combination of steroid and focal radiation therapy was used for treatment in four patients. RESULTS: Imaging and neuropathologic findings demonstrated a compressive optic neuropathy secondary to both epidural metastases and to deformity and hypertrophy of the optic canal due to metastatic cancer. Treatment was of benefit in three cases. CONCLUSION: Acute and subacute unilateral or bilateral optic neuropathy in patients with prostate cancer may be the result of optic canal metastases. Magnetic resonance imaging shows a characteristic pattern of bone hypertrophy and deformity with optic nerve compression. Early combination steroid and radiation therapy may induce long-lasting improvement.

Aged↗
PubMed2001

Optical effects of ocular surgery including anterior segment surgery.

Ocular surgery may alter the refraction and the corneal power of an eye. However, refraction and corneal power are not fundamental optical properties of the eye as such. Refraction is a fundamental property of a lens in front of the eye and an indirect or derived property of the eye, while corneal power is a fundamental property of only part of the eye. Nor are they the only clinically relevant paraxial optical effects of surgery. There are also effects on size, shape, and orientation of retinal images, for example, which are not simply related to refraction and corneal power. Quantitative analyses of the effects of surgery on the eye that account only for refraction and corneal power are necessarily incomplete. This paper offers an approach to the analysis of the optical effects of surgery that is complete within the limitations of paraxial optics. The key is the concept of the ray transference, which contains the 4 fundamental optical properties of an optical system. The surgery is represented by a hypothetical optical system, the anterior surgery-equivalent system, in front of the preoperative eye. The transference of this system, the anterior surgical transference, is a complete paraxial quantification of the optics of the surgery and is what needs to be studied in analyses of surgery. In this approach, ocular surgery in general is optically equivalent to a thick system placed in front of the preoperative eye. A simple model is developed for the case of anterior segment surgery in particular. In terms of the model, anterior segment surgery is shown to be equivalent to placing a thick bitoric lens in front of the preoperative eye. In particular cases, the surgery may be equivalent to an anterior thin lens. Astigmatism is an aspect of optical effects in general. It is not directly amenable to quantitative analysis in isolation; quantitative analyses of astigmatism should be done in terms of the concept of antistigmatism. In thin systems, astigmatism manifests only in power. However, in thick systems such as the eye, astigmatism can manifest in 4 fundamentally different ways. Among them are some phenomena currently described as irregular astigmatism. The foundation is laid for the complete analysis of paraxial astigmatism in general and in ocular surgery in particular.

Astigmatism↗
PubMed2006

Broad-band optical parametric gain on a silicon photonic chip.

Developing an optical amplifier on silicon is essential for the success of silicon-on-insulator (SOI) photonic integrated circuits. Recently, optical gain with a 1-nm bandwidth was demonstrated using the Raman effect, which led to the demonstration of a Raman oscillator, lossless optical modulation and optically tunable slow light. A key strength of optical communications is the parallelism of information transfer and processing onto multiple wavelength channels. However, the relatively narrow Raman gain bandwidth only allows for amplification or generation of a single wavelength channel. If broad gain bandwidths were to be demonstrated on silicon, then an array of wavelength channels could be generated and processed, representing a critical advance for densely integrated photonic circuits. Here we demonstrate net on/off gain over a wavelength range of 28 nm through the optical process of phase-matched four-wave mixing in suitably designed SOI channel waveguides. We also demonstrate wavelength conversion in the range 1,511-1,591 nm with peak conversion efficiencies of +5.2 dB, which represents more than 20 times improvement on previous four-wave-mixing efficiencies in SOI waveguides. These advances allow for the implementation of dense wavelength division multiplexing in an all-silicon photonic integrated circuit. Additionally, all-optical delays, all-optical switches, optical signal regenerators and optical sources for quantum information technology, all demonstrated using four-wave mixing in silica fibres, can now be transferred to the SOI platform.

Journal Article↗
PubMed2001

Laser thermal therapy: utility of interstitial fluence monitoring for locating optical sensors.

Multipoint optical fluence measurements can potentially be used to detect coagulation-induced changes in optical propagation during interstitial laser thermal therapy. Estimating the dimensions of coagulation using on-line optical monitoring, which is applicable to treatments where the tip of the source fibre is not precharred, may be limited by the accuracy of the placement of optical sensors with respect to source fibres. A strategy has been developed to determine accurately the position of a four-sensor linear array, prior to treatment, using optical fluence data obtained from the sensors for low-power (< or = 0.5 W) irradiation. A minimum of four sensors in an array was required in order to develop a mathematical formulation for position determination that did not require tissue optical properties or laser power as input. Optical propagation was based on diffusion theory for homogeneous tissues in spherical geometry. Low input laser power is needed to ensure that there are no thermally induced changes in tissue optical properties not accounted for in the mathematical description. Experimental evaluation was performed in a tissue-equivalent liquid phantom using 0.5 W of 805 nm optical energy and a translatable isotropic optical sensor. For sensor locations with 2 mm spacing, placement accuracy of 0.67 mm was achieved. The accuracy improved to 0.13 mm as the sensor spacing increased to 5 mm.

Hot Temperature↗
PubMed1991

Sensitivity of MST neurons to optic flow stimuli. II. Mechanisms of response selectivity revealed by small-field stimuli.

1. In these experiments we examined the receptive field mechanisms that support the optic flow field selective responses of neurons in the dorsomedial region of the medial superior temporal area (MSTd). Our experiments tested the predictions of two hypotheses of optic flow field selectivity. The direction mosaic hypothesis states that these receptive fields contain a set of planar direction-selective subfields that match the local directions of motion within optic flow fields. The vector field hypothesis states that these receptive fields are uniquely sensitive to distributed properties of planar, circular, or radial optic flow fields. 2. Experiments using large-field stimuli revealed that some neurons showed changes in optic flow field selectivity depending on the position of the stimulus in the receptive field; these are position-dependent responses. However, other neurons maintained the same optic flow field selectivities in spite of changes in stimulus position; these are position-invariant responses. We have used the position dependence or invariance of optic flow field selectivity as a way of testing the direction mosaic and vector field hypotheses. Position dependence is more consistent with the direction mosaic hypothesis, whereas position invariance is more consistent with the vector field hypothesis. 3. To test for position effects, we examined the optic flow field selectivity of small subfields within the large receptive fields of 160 MSTd neurons. First, we centered small-field optic flow stimuli of various sizes over the same position in the receptive field. Most MSTd neurons showed decreasing response amplitude with decreasing stimulus size but maintained optic flow field selectivity. 4. We then placed small-field stimuli at various positions within the large receptive field of these MSTd neurons. Position-invariant response selectivity was most prominent in single-component neurons, suggesting that they were more consistent with the vector field hypothesis. Position-dependent response selectivity was most prominent in triple-component neurons, suggesting that they were more consistent with the direction mosaic hypothesis. However, the variations in planar direction preference throughout the receptive field of these triple-component neurons were not consistent with a direction mosaic explanation of the large-field circular or radial selectivity observed. 5. Small-field position studies also demonstrated the existence of zones within the receptive field in which either direction-selective inhibitory or direction-selective excitatory responses predominated. The degree of overlap between these zones increased from nonselective to triple- to double- and finally to single-component neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1999

Complex spike activity of Purkinje cells in the ventral uvula and nodulus of pigeons in response to translational optic flow.

The complex spike (CS) activity of Purkinje cells in the ventral uvula and nodulus of the vestibulocerebellum was recorded from anesthetized pigeons in response to translational optic flow. Translational optic flow was produced using a "translator" projector: a mechanical device that projected a translational optic flowfield onto the walls, ceiling, and floor of the room and encompassed the entire binocular visual field. CS activity was broadly tuned but maximally modulated in response to translational optic flow along a "best" axis. Each neuron was assigned a vector representing the direction in which the animal would need to translate to produce the optic flowfield that resulted in maximal excitation. The vector is described with reference to a standard right-handed coordinate system, where the vectors, +x, +y, and +z represent, rightward, upward, and forward translation of the animal, respectively. Neurons could be grouped into four response types based on the vector of maximal excitation. +y neurons were modulated maximally in response to a translational optic flowfield that results from self-motion upward along the vertical (y) axis. -y neurons also responded best to translational optic flow along the vertical axis but showed the opposite direction preference. The two remaining groups responded best to translational optic flow along horizontal axes: -x + z neurons and -x-z neurons. In summary, our results suggest that the olivocerebellar system dedicated to the analysis of translational optic flow is organized according to a reference frame consisting of three approximately orthogonal axes: the vertical axis, and two horizontal axes oriented 45 degrees to either side the midline. Previous research has shown that the rotational optic flow system, the eye muscles, the vestibular semicircular canals and the postural control system all share a similar spatial frame of reference.

Animals↗
PubMed2002

Three-dimensional optoelectronic stacked processor by use of free-space optical interconnection and three-dimensional VLSI chip stacks.

We present a demonstration system under the three-dimensional (3D) optoelectronic stacked processor consortium. The processor combines the advantages of optics in global, high-density, high-speed parallel interconnections with the density and computational power of 3D chip stacks. In particular, a compact and scalable optoelectronic switching system with a high bandwidth is designed. The system consists of three silicon chip stacks, each integrated with a single vertical-cavity-surface-emitting-laser-metal-semiconductor-metal detector array and an optical interconnection module. Any input signal at one end stack can be switched through the central crossbar stack to any output channel on the opposite end stack. The crossbar bandwidth is designed to be 256 Gb/s. For the free-space optical interconnection, a novel folded hybrid micro-macro optical system with a concave reflection mirror has been designed. The optics module can provide a high resolution, a large field of view, a high link efficiency, and low optical cross talk. It is also symmetric and modular. Off-the-shelf macro-optical components are used. The concave reflection mirror can significantly improve the image quality and tolerate a large misalignment of the optical components, and it can also compensate for the lateral shift of the chip stacks. Scaling of the macrolens can be used to adjust the interconnection length between the chip stacks or make the system more compact. The components are easy to align, and only passive alignment is required. Optics and electronics are separated until the final assembly step, and the optomechanic module can be removed and replaced. By use of 3D chip stacks, commercially available optical components, and simple passive packaging techniques, it is possible to achieve a high-performance optoelectronic switching system.

Journal Article↗
PubMed2006

Surface plasmon resonance-based highly sensitive optical touch sensor with a hybrid noise rejection scheme.

A surface plasmon resonance (SPR)-based optical touch sensor structure is proposed that provides high switch sensitivity and requires a weak activating force. Our proposed SPR-based optical touch sensor is arranged in a compact Kretschmann-Raether configuration in which the prism acting as our sensor head is coated with a metal nanofilm. Our optical-based noise rejection scheme relies on wavelength filtering, spatial filtering, and high reflectivity of the metal nanofilm, whereas our electrical-based noise reduction is obtained by means of an electrical signal filtering process. In our experimental proof of concept, a visible laser diode at a 655 nm centered wavelength and a prism made from BK7 with a 50 nm thick gold layer on the touching surface are used, showing a 7.85 dB optical contrast ratio for the first touch. An estimated weak mechanical force of <0.1 N is also observed that sufficiently activates the desired electrical load. It is tested for 51 operations without sensor malfunction under typical and very high illumination of 342 and 3000 lx, respectively. In this case, a measured average optical contrast of 0.80 dB is obtained with a +/-0.47 dB fluctuation, implying that the refractive index change in a small 3.2% of the overall active area is enough for our SPR-based optical touch sensor to function properly. Increasing optical contrast in our SPR-based optical touch sensor can be accomplished by using a higher polarization-extinction ratio and a narrower-bandwidth optical beam. A controlled environment and gold-coated surface using the thin-film sputtering technique can help improve the reliability and the durability of our SPR-based optical touch sensor. Other key features include ease of implementation, prevention of a light beam becoming incident on the user, and the ability to accept both strong and weak activating forces.

Journal Article↗
PubMedDate not supplied

Comparison of videokeratographic functional optical zones in conductive keratoplasty and laser in situ keratomileusis for hyperopia.

PURPOSE: To compare the videokeratographic functional optical zone of eyes treated with conductive keratoplasty to eyes treated with laser in situ keratomileusis (LASIK) for hyperopia. METHODS: Sixteen eyes treated with conductive keratoplasty for hyperopia were retrospectively evaluated to determine the size of the videokeratographic functional optical zone. The functional optical zone of these eyes was compared to the functional optical zone of 16 eyes that underwent LASIK for hyperopia with the VISX S2 excimer laser, for comparable amounts of hyperopia. The functional optical zone was measured at the edge of central corneal steepening and paracentral flattening on videokeratography 3 to 6 months after surgery. RESULTS: The functional optical zone after surgery measured an average of 5.6 mm horizontally and 5.6 mm vertically in the conductive keratoplasty eyes, and 4.7 mm horizontally and 5.1 mm vertically in the hyperopic LASIK eyes (P<.001 and P<.005). The mean functional optical zone area was 31.1 mm2 in the conductive keratoplasty eyes and 24.6 mm2 in the hyperopic LASIK eyes (P<.001). The functional optical zone created by conductive keratoplasty had more uniform central steepening and less peripheral blending than the functional optical zone created by hyperopic LASIK. CONCLUSION: Conductive keratoplasty was effective at creating central steepening in the cornea. The functional optical zone resulting from conductive keratoplasty was significantly larger than that obtained with hyperopic LASIK using the VISX S2 excimer laser.

Adult↗
PubMedDate not supplied

Hyperopic laser in situ keratomileusis with 5.5-, 6.5-, and 7.0-mm optical zones.

PURPOSE: To evaluate the results of laser in situ keratomileusis (LASIK) for the correction of hyperopia and hyperopic astigmatism using a large 7.0-mm optical zone and to compare them with treatments using a 5.5- and 6.5-mm optical zone. METHODS: One hundred sixty-one eyes of 89 patients with a mean preoperative spherical equivalent refraction of +2.44 +/- 1.32 diopters (D) (range: +0.00 to +5.62 D, cylinder 5.25 to 0.00 D) were treated for hyperopia and hyperopic astigmatism using a 7.0-mm optical zone and were analyzed retrospectively. Postoperatively, patients were examined after 1 day, 1 week, 1 month, 3 months, and 1 year. Eyes treated previously at the same center by the same surgeons with 5.5- and 6.5-mm optical zone applications were used as controls. All treatments were performed with the Nidek EC 5000 CXII excimer laser system (Nidek, Gamagori, Japan). A nasal hinged flap was created using the Nidek MK 2000 microkeratome in all cases. RESULTS: The mean postoperative spherical equivalent refraction after 1 month (n=89) was +0.12 +/- 0.72 D (range: -1.75 to +2.75 D), +0.13 +/- 0.74 D (range: -1.88 to +1.62 D) at 3 months (n=70), and +0.20 +/- 0.69 D (range: -1.62 to +1.12 D) at 1 year (n=33). Regression between 1 month and 1 year was 0.08 D in the 7.0-mm optical zone group. Regression was 0.25 D in the 5.5-mm group and 0.02 D in the 6.5-mm optical zone group between 1 month and 1 year. In both the 5.5- and 6.5-mm optical zone groups, 13% of eyes lost one line in visual acuity (2% in the 7.0-mm optical zone group). The gain of one or more lines in visual acuity was 19% in the 5.5-mm group, 17% in the 6.5-mm group, and 27% in the 7.0-mm optical zone group. All data represent primary cases without retreatment. CONCLUSIONS: Increasing the optical zone size from 5.5 mm to 6.5 mm and to 7.0 mm seems to improve refractive results, stability, and safety of hyperopic and hyperopic-astigmatic LASIK treatments. Although some hyperopic and astigmatic eyes are endangered by loss of lines in best spectacle-corrected visual acuity, more eyes gain one or more lines.

Adult↗
PubMed2000

Gradients of ephrin-A2 and ephrin-A5b mRNA during retinotopic regeneration of the optic projection in adult zebrafish.

Regeneration of optic axons in the continuously growing optic system of adult zebrafish was analyzed by anterograde tracing and correlated with the mRNA expression patterns of the recognition molecules ephrin-A2 and ephrin-A5b in retinal targets. The optic tectum and diencephalic targets are all reinnervated after a lesion. However, the rate of erroneous pathway choices was increased at the chiasm and the bifurcation between the ventral and dorsal brachium of the optic tract compared to unlesioned animals. Tracer application to different retinal positions revealed retinotopic reinnervation of the tectum within 4 weeks after the lesion. In situ hybridization analysis indicated the presence of rostral-low to caudal-high gradients of ephrin-A2 and ephrin-A5b mRNAs in unlesioned control tecta and after a unilateral optic nerve lesion. By contrast, the parvocellular superficial pretectal nucleus showed retinotopic organization of optic fibers but no detectable expression of ephrin-A2 and ephrin-A5b mRNAs. However, a row of cells delineating the terminal field of optic fibers in the dorsal part of the periventricular pretectal nucleus was intensely labeled for ephrin-A5b mRNA and may thus provide a stop signal for ingrowing axons. Ephrin-A2 and ephrin-A5b mRNAs were not detectable in the adult retina, despite their prominent expression during development. Thus, given a complementary receptor system in retinal ganglion cells, expression of ephrin-A2 and ephrin-A5b in primary targets of optic fibers in adult zebrafish may contribute to guidance of optic axons that are continuously added to the adult projection and of regenerating axons after optic nerve lesion.

Age Factors↗