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Achromatopsia
Published in Alexander R. Toftness, Incredible Consequences of Brain Injury, 2023
As is more relevant to this book about acquired conditions, it is also possible to be born with typical color vision but then lose it later in life due to brain damage. When severe colorblindness exists due to damage to the brain's cerebral cortex, it is called cerebral achromatopsia. In a person with cerebral achromatopsia, their eyes may be no different from a typical person's eyes. That is, the wavelengths of light are entering into their eyes, are turned into signals by the cone cells of the retina, and are sent into the brain. But the brain has forgotten how to turn those signals into perceptions of color. Because of this, these people typically lose the ability to even imagine colors (see Aphantasia), but there are exceptions (Bartolomeo et al., 1997).
Screening Programs
Published in Ching-Yu Cheng, Tien Yin Wong, Ophthalmic Epidemiology, 2022
Jakob Grauslund, Malin Lundberg Rasmussen
Color vision can also be tested in children, in order to guide those with color vision deficiency in terms of future job planning, as some professions are excluded if color vision deficiency is present (e.g., pilot and train driver) (27).
Spectral Imaging Technologies and Apps and Dual-Layer Detector Solution
Published in Katsuyuki Taguchi, Ira Blevis, Krzysztof Iniewski, Spectral, Photon Counting Computed Tomography, 2020
Nadav Shapira, Yoad Yagil, Naor Wainer, Ami Altman
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.
Ocular side effects of systemic isotretinoin – a systematic review and summary of case reports
Published in Journal of Dermatological Treatment, 2023
Olivia Lamberg, Arianna Strome, Foster Jones, Julia Mleczek, Adrienne Jarocki, Jonathon P. Troost, Yolanda Helfrich
Vision changes included visual acuity change, refractive vision changes, nyctalopia, and abnormal color vision. Nine studies (4684 total patients) reported the proportion of patients experiencing visual acuity changes (1,68,74,78–80,92–94). The overall reported incidence is 3% (95% CI: 0%, 4%) with heterogeneity of p < 0.01 (Figure 3.10). Six studies (4211 total patients) reported the proportion of patients experiencing nyctalopia (1,70,78,93,95,96). The overall reported incidence is 1% (95% CI: 0%, 3%) with heterogeneity of p < 0.01 (Figure 3.11). Three studies (85 total patients) reported the proportion of patients experiencing refractive vision change (94,97,98). The overall reported incidence is 0% (95% CI: 0%, 3%) with heterogeneity of p = 0.99 (Figure 3.12). Three studies (111 total patients) reported the continuous refractive vision changes from before and during isotretinoin treatment (81,99,100). There was an overall −0.08 change (95% CI: −0.23, 0.05) after initiation of isotretinoin treatment (Figure 3.13). Two studies (43 total patients) reported the proportion of patients experiencing abnormal color vision deficiency (68,101). The overall reported incidence is 2% (95% CI: 0%, 8%) (Figure 3.14). Overall, in unique 18 studies reporting on 5265 total patients, the overall reported incidence of vision changes ranged from 0–3%, with 3 studies reporting a 0.08 decrease in refractive vision associated with isotretinoin.
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.
Masking Colour Blindness: A Case Report
Published in Neuro-Ophthalmology, 2023
Antonia Kartika, Raisha Pratiwi Indrawati, Angga Kartiwa, Rusti Hanindya Sari, Dianita Veulina Ginting, Prettyla Yollamanda
Colour vision is important for some occupations that need good colour discrimination. Identification of colours requires normal function of photoreceptors containing visual pigment responsible for short (blue), medium (green), and long (red) wavelengths, which are the S-cones, M-cones, and L-cones, respectively. Normal colour vision is known as trichromacy.4 However, if one of this photoreceptors is absent or defective, dysfunction in colour perception will be present. Anomaly of a photoreceptor is known as anomalous trichromacy, absence of one of the photoreceptor cones is called dichromacy, and absence of two of the photoreceptor cones is called monochromacy. Anomalous trichromacy can cause tritanomaly, deuteranomaly, or protanomaly. Dichromacy can cause tritanopia, deuteranopia, or protanopia. Monochromacy, which is caused by the absence of red and green cones, is called blue cone monochromacy. The absence of all cones is called achromatopsia or total colour vision loss.1,2,5 Red-green colour deficiency is the most prevalent form of CVD. Red-green CVD is caused by the absence of M-cones or L-cones, causing deuteranopia and protanopia, respectively.6 In this condition, there are overlapping of green and red wavelength bands received by cone photoreceptors, causing abnormality of deutan and protan colour perception.