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Measurement and Analysis Techniques for Three-Dimensional Eye Movements
Published in Michael Fetter, Thomas Haslwanter, Hubert Misslisch, Douglas Tweed, Three-Dimensional Kinematics of Eye, Head and Limb Movements, 2020
While the horizontal and vertical components of eye position determine what we look at, and can be measured and analyzed with mostly the same methods, the additional measurement of ocular torsion requires not only new measurement techniques, but also new concepts in the analysis of the data. A number of measurement techniques have been used to determine the torsional component of eye position, like afterimages (Helmholtz, 1867), methods using the blind spot (Colenbrander, 1963) or the axis of astigmatism (Kushner and Kraft, 1983), search coils, and video-images. While afterimages are still occasionally used (Kushner and Kraft, 1983; Probst-Müller et al., 1996), only the last two methods are now commonly employed. Since the mathematical concepts used in the analysis of three-dimensional eye position data have been summarized recently (Haslwanter, 1995) this article will concentrate on practical aspects of the measurement of three-dimensional eye position and -velocity with search coils or video systems, and on the analysis of 3D data.
Revisioning Cellular Bioenergetics
Published in Aruna Bakhru, Nutrition and Integrative Medicine, 2018
The eye itself, which is continually exposed to ambient powerful photons that pass through various ocular tissues, emits spontaneous and visible light-induced ultraweak photon emissions (Wang et al., 2011). It has even been hypothesized that visible light induces delayed bioluminescence within the exposed eye tissue, providing an explanation for the origin of the negative afterimage (Bókkon et al., 2011).
Contrast adaptation
Published in Pablo Artal, Handbook of Visual Optics, 2017
A similar study was performed by Sawides et al. (2011). They selected subjects with highly different levels of higher-order aberrations, with the RMS wavefront errors ranging from about 0.1 to 0.4 μm, and Strehl ratios (= the ratio of the area under the real modulation transfer function divided by the area under the diffraction-limited modulation transfer function) ranging from 0.097 to 0.193. The Strehl ratios show that the optical transfer functions were only about 10%–20% of the diffraction-limited transfer functions, which means not very good optics anyway. Two major results came out of these studies: (1) subjects with poorer optics judged images as sharp even if they were more blurry, compared to subjects with better optics who required images to contain more energy at higher spatial frequencies to judge them as sharp (this let the authors chose the title of the paper as Vision Is Adapted to the Natural Level of Blur Present in the Retinal Image), and (2) the adapting image may differ from the test image without that the amplitude of adaptation is reduced. This finding is in line with findings by Webster et al. (Figure 21.12) and excludes that afterimages played a role in the studied effects.
Static cervico-ocular reflex in healthy humans
Published in Acta Oto-Laryngologica, 2023
Tomoki Ooka, Keiji Honda, Takeshi Tsutsumi
Our results for static COR did not coincide with those of a previous report’s [12]. In the previous report, the participants were seated on a chair that could be tilted laterally up to 15° in increments of 5° with their heads fixed by a holder. Eye torsions were assessed using afterimages. Significant eye torsion was found in four patients with bilateral vestibular loss, but not in 12 healthy participants. On the other hand, our participants stabilised their trunks by placing the tilted side of the body against the bed, which was tilted up to a maximum of 45° in 15° steps, and eye torsions were examined using an infrared CCD goggle. In Experiment 1, static COR increased as the trunk tilt increased, suggesting that eye torsion increases as cervical inputs are reinforced. Two reasons may potentially account for why static COR appeared even at a trunk tilt of 15° in our study: (1) the tension in the neck muscles was stronger in our study because our participants voluntarily moved their head against the trunk; and (2) eye torsions were captured by infrared CCD goggles, which can directly evaluate eye movement and has a high accuracy that even eye rotations of 1 to 2° could be detected with a significant difference compared to the reference position.
About the stereoscopic phenomena and Wheatstone’s attack on the theory of the identical points of the retinas: Part 2
Published in Strabismus, 2022
Wheatstone further states that when he drew the stereoscopic images in color on a background of its complementary color and then looked at the stereoscopic image for some time, he would then alternately see the afterimage of one drawing and of the other with his eyes closed. However, at the moment when both appeared at the same time, he saw the afterimage of the stereoscopic image in relief. He says that in this experiment one must strictly fixate one point of the image in the stereoscope. When I do this, I see other parts of the image twice and, after closing my eyes, I see the afterimage of the part which I saw single in the stereoscope in all its energy, followed by vaguer lines, which at one moment seem to belong to one double image, then to the other. On the other hand, if I leave my visual distance [vergence] so much leeway that I can see single under all circumstances, the afterimage resembles the stereoscopic image. These are results that agree both with the theory of the identical points of the retinas, with du Tour’s experiments 5 and with the conclusions drawn by Müller 3(p80) from these experiments and from his own experiments.
What diagnosis should we make for long-lasting vertiginous sensation after acute peripheral vertigo?
Published in Acta Oto-Laryngologica, 2020
Tomoyuki Shiozaki, Masaharu Sakagami, Taeko Ito, Ichiro Ota, Yoshiro Wada, Tadashi Kitahara
ieMRI at 4 h after intravenous administration of gadolinium was previously reported to be useful for imaging of EH [9]. In the present study, all patients received heavy T2-weighted MRI cisternography for an anatomical reference of the total lymph fluid, heavy T2-weighted (hT2W) three-dimensional fluid-attenuated inversion recovery sequences with a 2250 ms inversion time for positive perilymph images, and heavy T2-weighted three-dimensional inversion recovery with a 2050-ms inversion time for positive endolymph images. After image acquisition, we obtained a hybrid image of the reversed image of the positive endolymph signal and the negative image of the positive perilymph signal after motion correction by subtracting the positive endolymph images from positive perilymph images. In this protocol, pixels with a negative value were estimated as representing EH.