Spectral Imaging Technologies and Apps and Dual-Layer Detector Solution
Katsuyuki Taguchi, Ira Blevis, Krzysztof Iniewski in Spectral, Photon Counting Computed Tomography, 2020
Following the principle of natural selection, two kinds of photoreceptor cell evolved with different energy response. While these new types of photoreceptor cells still maintain the basic mechanism of response that is dependent on the total amount of absorbed energy, each type exhibits a different spectral sensitivity, i.e., different detection efficiencies for the same light spectrum. That is, not to say that there is a complete energy separation between the two spectral responses, but that, despite the partial overlap between the two response spectra, a different detection signal is produced by each type of photoreceptor cell. This new scheme allowed for the differentiation between objects or surfaces that presented little or no signal difference in the one-dimensional scheme and provided an evolutionary advantage in various situations. The interpretation of the signals by the brain is now referred to as color vision, which combines information of both the integrated energy and the wavelength contrasts to detect objects for signals from cells, or channels, in the same areas of visual space. When the integrated energy contrast between different objects is absent or insufficient, “wavelength contrast” [1] may still be available to differentiate between them – it may be that two objects reflect the same amount of energy; however, it is unlikely that they reflect the same wavelength composition.
Toxins in Neuro-Ophthalmology
Vivek Lal in A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Toxicity includes keratopathy, ciliary body involvement, lens opacities and retinopathy. Retinopathy is the major concern although others are more common but benign. Risk factors of retinopathy include age, daily as well as cumulative dosage, treatment duration and coexisting retinal, renal or liver disease. Visual symptoms include decreased vision, missing central vision, glare, blurred vision, light flashes and metamorphopsia. Characteristic fundus finding is bull's-eye maculopathy. All patients have field defects including paracentral, pericentral, central and peripheral field loss. Color vision is impaired in the advanced stage. Regular screening may be necessary to detect reversible premaculopathy. Cessation of the drug is the only effective management of the toxicity.
Nutrition and the Cancer Patient
David Heber, Zhaoping Li in Primary Care Nutrition, 2017
We are now separated from the system that enabled us to select foods according to color and taste. Humans and a few primate species have trichromatic color vision, so that they are able to distinguish red from green (Dominy and Lucas 2001). All other mammals have dichromatic vision and cannot distinguish between the two colors. One hypothesis for the evolution of this visual ability was that it conferred an advantage by enabling primates to distinguish red fruits from the green background of forest leaves. We could joke that today colors are still used to promote food choices, as most fast-food restaurants package their beige french fries in a red cardboard package. Contrasting colors have been shown to be one of the key factors in food selection by Drewnowski (1996). A new method for selecting fruits and vegetables based on colors keyed to the content of phytochemicals is described as a way of translating the science of phytochemical nutrition into dietary guidelines for the public. Most Americans eat only two to three servings of fruits and vegetables per day, without regard to the phytochemical contents of the foods being eaten. Certain phytochemicals give fruits and vegetables their colors and also indicate their unique physiological roles. All the colored phytochemicals that absorb light in the visible spectrum have antioxidant properties. In artificial membrane systems, it is possible to show synergistic interactions of lutein and lycopene in antioxidant capacity, and there are well-known antioxidant interactions of vitamins C and E based on their solubility in hydrophilic and hydrophobic compartments of cells.
Relation between smoking and visual processing in bipolar disorder
Published in Journal of Addictive Diseases, 2022
Milena E. C. Oliveira, Natalia L. Almeida, Thiago P. Fernandes, Natanael A. Santos
Acquired color vision impairments can lead to visual and cognitive dysfunctions, either through the neural or systemic pathways.1 Color vision is mediated by the cones, and they are responsible for the activation of horizontal and bipolar postsynaptic cells, transferring their signals to ganglion cells, and playing an important role in visual processing and, subsequently, cognitive processing.2 Chromatic information (i.e., related to color processing) is mediated by three types of cones, namely long (L), medium (M) and short (S) wavelength-sensitive cones, which are connected to two different visual pathways: parvocellular and koniocellular. Briefly, the parvocellular pathway is associated to L- and M-cones, related to the red-green system. The koniocellular pathway is composed of S-cones, but also for the L- and M-cone responses, and is believed to carry information related to the blue-yellow system.3
Ocular Manifestations After Acute Methanol Poisoning
Published in Neuro-Ophthalmology, 2023
Maamouri Rym, Nabi Wijden, Maamouri Héla, Sassi Héla, Brahmi Nozha, Monia Cheour
This is a case series including patients diagnosed with acute methanol poisoning following the ingestion of cologne and adulterated alcohol from an illicit production who were hospitalised in the department of intensive care medicine and clinical toxicology (CAMU) in Tunis, Tunisia, during an outbreak in 2020. All patients underwent a complete ophthalmological examination in the ophthalmology department of Habib Thameur hospital in Tunis, Tunisia, including measurement of best-corrected Snellen visual acuity (VA), pupillary examination, Lanthony Desaturated D-15 colour vision testing, automated 24–2 visual field testing, slit-lamp examination and dilated fundus examination. Normal colour vision was defined as normal trichromacy and defective colour vision was defined as mild, moderate or severe abnormal trichromacy or dichromacy. Reliability indices (name, demographic data, fixation loss, false positive and false negative) were verified before interpretation of the automated visual fields. Mean retinal nerve fibre layer (RNFL) thickness was assessed from images acquired using the swept source optical coherence tomography (OCT) (DRI-OCT-1, Topcon, Tokyo, Japan). The study protocol followed the tenets of the Declaration of Helsinki.
Effect of Background Luminance Level on the Assessment of Color Visual Acuity Using Colored Landolt Rings in Young Healthy Subjects
Published in Current Eye Research, 2018
Yoshiki Tanaka, Sho Yokoyama, Rie Horai, Takashi Kojima, Sato Hiroyuki, Yukihito Kato, Mari Takagi, Hideki Nakamura, Kiyoshi Tanaka, Kazuo Ichikawa, Shoko Tanabe
In conclusion, the current study shows that our CVA testing system can effectively measure the visual function for colors by equalizing the luminance between the background and the Landolt rings. The blue–yellow axis colors showed remarkably worse CVA (higher LogMAR value) than the other colors. Since the blue–yellow axis colors are derived from S-cones, the CVA testing system may be able to evaluate and quantify the visual function of each individual cone type. Acquired color vision deficiencies can result from abnormality in any part of visual pathway. Cataract, glaucoma, retinal disease, optic nerve disease, cerebral disease and aging may produce color vision deficiencies. We believe that CVA assessment may be useful for individuals who have known or suspected ocular dysfunction or color vision deficiencies. In addition, it is also useful for understanding the visual function of elderly people. Verification of CVA for acquired color vision deficiencies is our future work.
Related Knowledge Centers
- Eye
- Photoreceptor Cell
- Visual Perception
- Visual System
- Ultraviolet
- Brain
- Evolution of Color Vision
- Visible Spectrum
- Just-Noticeable Difference
- Scotopic Vision