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Retinal Surface (retinal + surface)
Selected AbstractsHow the parallel channels of the retina contribute to depth processingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2007Peter H. Schiller Abstract Reconstructing the third dimension in the visual scene from the two dimensional images that impinge on the retinal surface is one of the major tasks of the visual system. We have devised a visual display that makes it possible to study stereoscopic depth cues and motion parallax cues separately or in concert using rhesus macaques. By varying the spatial frequency of the display and its luminance and chrominance, it is possible to selectively activate channels that originate in the primate retina. Our results show that (i) the parasol system plays a central role in processing motion parallax cues; (ii) the midget system plays a central role in stereoscopic depth perception at high spatial frequencies, and (iii) red/green colour selective neurons can effectively process both cues but blue/yellow neurons cannot do so. [source] Low sensitivity of retina to AMPA-induced calcificationJOURNAL OF NEUROSCIENCE RESEARCH, Issue 4 2003Noemí Andrés Abstract Glutamate is involved in most CNS neurodegenerative diseases. In particular, retinal diseases such as retinal ischemia, retinitis pigmentosa, and diabetic retinopathy are associated with an excessive synaptic concentration of this neurotransmitter. To gain more insight into retinal excitotoxicity, we carried out a dose,response study in adult rats using ,-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), a glutamate analogue. AMPA intraocular injections (between 0.27 and 10.8 nmol) caused no morphologic modification, but a 10.8 + 21 nmol double injection in a 10-day interval produced a lesion characterized by discrete neuronal loss, astroglial and microglial reactions, and calcium precipitation. Abundant calcium deposits similar to those present in rat and human brain excitotoxicity or hypoxia-ischemia neurodegeneration were detected by alizarin red staining within the retinal surface and the optic nerve. Glial reactivity, associated normally with astrocytes in the nerve fiber, was assessed in Müller cells. GABA immunoreactivity was detected not only in neuronal elements but also in Müller cells. In contrast to the high vulnerability of the brain to excitotoxin microinjection, AMPA-induced retinal neurodegeneration may provide a useful model of low central nervous system sensitivity to excitotoxicity. © 2003 Wiley-Liss, Inc. [source] Unilateral choroidal excavation in the macula detected by spectral-domain optical coherence tomographyACTA OPHTHALMOLOGICA, Issue 3 2010Yuka Wakabayashi Abstract. Purpose:, To report clinical findings of three patients with unilateral peculiar choroidal excavation in the macula detected by spectral-domain (SD) optical coherence tomography (OCT). Methods:, Three cases with unilateral choroidal excavation in the macula detected by SD OCT. Fluorescein angiography (FA), indocyanine green angiography (IA), ultrasonography, visual field tests and multifocal electroretinography (mfERG) were performed. Results:, Although all three patients complained of metamorphopsia, visual acuity and central visual field were normal in the affected eyes. SD OCT demonstrated choroidal excavation in the macula despite a normal foveal contour along the inner retinal surface. The excavation involved the outer retinal layers up to the external limiting membrane in cases 1 and 2, while only the retinal pigment epithelium was involved in case 3. The excavation corresponded to foveal pigment mottling in cases 1 and 2 and to a parafoveal yellowish fusiform lesion in case 3. The lesions appeared hypoautofluorescent and unremarkable in FA except for circumferential hyperfluorescence in case 3 and hypofluorescent in IA. B-scan ultrasonography was unremarkable. MfERG in cases 1 and 2 was normal. Conclusions:, SD OCT demonstrated two types of choroidal excavation in the macula. More case accumulation and a longer follow-up will elucidate the pathogenesis and prognosis of the lesions. [source] Principle of adaptive opticsACTA OPHTHALMOLOGICA, Issue 2009PG SÖDERBERG Purpose To provide an overview of adaptive optics imaging of the retina. Methods In ophthalmoscopical imaging, the two dimensional spatial radiance variation of the back scattered light from the retinal surface is measured. Perfect imaging would require that light backscattered from one point on the retina examined is refocused to one point on the detector. Due to diffraction, light scattering and aberrations, some of the light, injected into the eye examined and some of the light back scatted from the retina examined, are deviated. This leads to loss of contrast. Aberrations induced are, for each individual, specific to the optics of the eye examined. In AOSLO, in addition to confocal illumination and light detection, aberrations induced by the optics of the eye examined are individually measured by wave front sensing and corrected for. Results In the AOSLO, a wave front sensor is introduced between the light source and the eye examined. The information from the wave front sensor is fed back to a deformable mirror, also placed in between the light source and the eye examined. The deformable mirror corrects the wave front aberrations induced by the optics of the eye examined. This allows the injected light to form a point on the retinal surface and simultaneously, the backscattered light from the retina of the eye examined to be focused to a point on a detector. An x-y scanner in front of the eye allows sequential illumination and capturing of aberration minimized back scattered light from an x-y matrix of the retinal surface of the eye examined. The relative radiances measured in the x-y matrix represent the image. Conclusion Adaptive optics in ophthalmoscopy improves contrast in the image of the retina examined by correcting for aberrations induced by the optics of the eye examined. [source] Optical coherence tomography of chorioretinal and choroidal foldsACTA OPHTHALMOLOGICA, Issue 3 2007Giuseppe Giuffrè Abstract. Purpose:, To report the optical coherence tomography (OCT) findings in cases of chorioretinal and choroidal folds. Methods:, Eight subjects with folds of the fundus of the eye were examined with fundus photography, fluorescein angiography, B-scan ultrasonography and Stratus OCT. Results:, Two types patterns were found on OCT. Five cases showed undulating retinal as well as retinal pigment epithelial lines of normal thickness; these were defined as chorioretinal folds. The posterior vitreous surface often adhered to the crests of the folds only. Three cases exhibited a wavy appearance of the retinal pigment epithelium and a flat retinal surface; these were classified as choroidal folds. Conclusions:, Scanning by OCT can differentiate chorioretinal folds from choroidal folds and reveal the relationships between the folds and the posterior vitreous surface. [source] Computer-assisted training system for pars plana vitrectomyACTA OPHTHALMOLOGICA, Issue 6 2003Jost B. Jonas Abstract. Purpose:,To evaluate whether microsurgical steps in vitreoretinal surgery can be taught by a computer-assisted training system. Methods:,This prospective, randomized experimental study included 14 ophthalmic residents and medical students who were completely inexperienced in microsurgery. They were randomized into two groups. The study group underwent training programmes in a computer-assisted training system for simulation of pars plana vitrectomy. The control group did not participate in any in vitro training. In the second phase of the study, participants of both groups performed a pars plana vitrectomy in three pig eyes, which included picking a metallic foreign body from the retinal surface. Results:,The amount of retinal detachment and the number of retinal defects at the end of the vitrectomies were smaller, the time needed to remove the foreign body was shorter, the number of retinal lesions associated with the foreign body removal was lower, and the mark given was better in the trained study group than in the untrained group. The relatively small number of study participants did not allow the differences between the study and control groups to reach the 5% level of error probability. Conclusions:,In an animal model, training by a computer-based medical work station for simulation of pars plana vitrectomy showed better outcome measures for trained study participants compared with untrained study participants. Future studies may show whether further refinements of such training programmes will result in statistically significantly better results in surgical outcome parameters. [source] | ||||||||||