Chemosensory Disorders and Nutrition
Alan R. Hirsch in Nutrition and Sensation, 2023
Thus, variability of olfactory ability is a continuum. Such a heterogeneous condition is highlighted in the concept of normal olfaction. An example in another sensory system can be observed in vision. Visual acuity is relatively homogenous in the general population, where 20/20 is defined as the normal value. On the other hand, two standard deviations from the population mean, the definition of normal olfactory ability, is so widespread, that two individuals can still be considered in the normal range, even though one individual’s olfactory ability may be one thousand times better than the other. Hence, identification tests of olfactory ability may be classified as normosmia, but the previously nasute individual would perceive as severely reduced (Hirsch 1995a). This is much more complex due to the lack of a few pure odors (like only three colors), but rather the presence of a virtual aromatic kaleidoscope continuously bombarding the proboscis—a literal universe of kippage at the tip of the nose. Moreover, odors blend and diffuse together, with a normosmic normal able to detect over one trillion unique odors (Keller, Dushdid, Magnasco, and Vosshall 2014).
Eyesight standards for beach lifeguards
Mike Tipton, Adam Wooler in The Science of Beach Lifeguarding, 2018
The most commonly used, rapid, simple and economical test of visual acuity is the optotype or chart test. One such test is the Snellen chart (rows of letters of decreasing font size [3]); other opto-type alternatives include the Landolt C, Sloan, BSI (British Standard Institution) and E charts. The standard definition of visual acuity is the ability of the eye to resolve a spatial pattern separated by a visual angle of one minute of arc. With the Snellen chart, normal visual acuity is recorded as 20/20 (feet) or 6/6 (metres) using a diffusely illuminated chart without glare. This means that at 6 m the test subject should be able to see the same as a ‘normal’ person with good eyesight. A score of 6/12 means that a test subject can see the same at 6 m as a ‘normal’ person with good eyesight can see at 12 m. The maximum acuity of the human eye without visual aids is generally thought to be about 6/4. The Snellen fraction may also be expressed as a decimal, where 6/6 =1; 6/12 = 0.5.
Vision Impairment and Its Management in Older Adults
K. Rao Poduri in Geriatric Rehabilitation, 2017
Vision is a complex entity that is often subjective in its measurement and definition. A common way to measure vision is by measuring visual acuity on a standardized vision chart. Visual acuity measures the ability to distinguish details and measures the clarity of vision. While one’s visual acuity may be very good even at older ages, contrast sensitivity or the ability to see low contrast patterns, such as faces, is an example of a measure of vision that is very sensitive to aging and can decrease overtime after age 60 years, often due to the presence of a cataract. Measuring the visual field is another way to assess ocular function, and the area of vision may be reduced peripherally, paracentrally, or centrally due to retinopathy, macular degeneration, or glaucoma, loss of optic nerve tissue associated often with relative increased intraocular pressure and aging in the eye. Aging may also impact the oculomotor ability for fixation and tracing. These involve the ability to focus on a fixed point and are important for reading. Recovery of visual function after being subject to bright light or glare is more of a problem in the older population often due to cataract. Stereo acuity or fine detail depth perception and color vision may also be impacted due to changes associated with aging affecting the eye and visual system.
Association Between Ocular Trauma and Activation of Ocular Toxoplasmosis
Published in Ocular Immunology and Inflammation, 2023
Sebastián Inchauspe, Agustina Palacio, Graciela Arriazu, Marcela Bellón, Víctor Morales Roldan, Pedro Torres de Leon, Stefani L. Olivera Plata, Emilio M. Dodds
Of those 10 patients, four patients had traumatic head injuries; four of them suffered blunt eye trauma, and two patients had corneal foreign bodies. Toxoplasma IgG was positive in eight patients and was not recorded in the medical records of the remaining two patients. However, all patients had clinical manifestations compatible with ocular toxoplasmosis and had a good response to treatment with the classic combination of pyrimethamine, sulfadiazine or azithromycin and oral prednisone 40–80 mg daily. Six patients resolved within three to seven weeks and two patients required long term therapy to heal (12 and 14 weeks respectively). One of them was HIV+ and the other one, despite being immunocompetent, required four injections of intravitreal clindamycin in addition to systemic treatment with pyrimethamine and azithromycin. Only data from the first visit were available for one patient without further follow-up. In the remaining nine patients, the average follow-up was 14.22 months (range 1–34). Visual acuity improved in six patients and remained unchanged in three.
Diurnal Variation of Corneal Dendritic Cell Density
Published in Current Eye Research, 2022
Sultan Alotaibi, Jerome Ozkan, Eric Papas, Maria Markoulli
At the midday visit, the Ocular Surface Disease Index (OSDI) questionnaire was used to ensure that participants did not display symptoms of dry eye disease (i.e. OSDI <13).23,24 Participants with OSDI scores >13 were excluded from the study. Visual acuity was measured using a computerized logMAR letter chart viewed at a distance of three meters. Assessments of bulbar and limbal redness were performed using biomicroscopy and graded according to the Brien Holden Vision Institute Grading scales.25 Corneal staining was assessed using saline moistened fluorescein strips (Fluorets ophthalmic strips, 1 mg; Chauvin Pharmaceuticals, Essex, England). Following these procedures, images of corneal dendritic cells were obtained using a confocal microscope (Heidelberg Retinal Tomograph III with Rostock Corneal Module; Heidelberg Engineering GmbH, Heidelberg Germany). The imaging procedure was repeated before sleep and upon awakening, followed by corneal staining, in each case, to evaluate postprocedure corneal integrity.
Fear of falling avoidance behavior affects the inter-relationship between vision impairment and diminished mobility in community-dwelling older adults
Published in Physiotherapy Theory and Practice, 2022
Szu-Ping Lee, Ya-Wen Hsu, Lauren Andrew, Talia Davis, Christian Johnson
The second part of the testing procedure was to test the participant’s VA using the Snellen chart. Participants stood 20 ft. (~6 m) from a well-illuminated flat wall on which the eye exam chart was secured and were instructed to read the lowest visible line (Stevens, 2007). Participants were instructed to cover one eye with their hand while the uncovered eye was tested, and then repeat the process with the other eye. If a participant made more than one error while reading the selected line, they were instructed to read the line above. This was repeated until the lowest visible line was accurately reported by the participant. Normal visual acuity is termed 20/20, indicated by a specific line on the Snellen chart. Larger number behind the fraction line indicates worse visual acuity (e.g. 20/40, 20/60 … etc.) Participants were allowed to wear corrective eye lenses for both the TUG test and the VA test if they typically wore them for community ambulation.
Related Knowledge Centers
- Cornea
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- Far-Sightedness
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