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Gene Therapy and Gene Correction
Published in Yashwant V. Pathak, Gene Delivery Systems, 2022
Manish P. Patel, Sagar A. Popat, Jayvadan K. Patel
Sight is the most prominent of the senses. Certain gene mutations can lead to a degenerative effect on the human retina (Singh et al. 2018). Leber congenital amaurosis (LCA) is a disease that is usually verified in newborns and toddlers. With this disease, patients have severely impaired vision and abnormal ocular movements (nystagmus). Dozens of mutated genes cause LCA, but six main ones induce LCA in more than 50% of the population. They are embryonic development (CRX), photoreceptor cell structure (CRB1), phototransduction (GUCY2D), protein trafficking (AIPL1, RPGRIP1) and vitamin A metabolism (RPE65) (Morimura et al. 1998). Out of all these, the RPE65 gene is the main target for gene therapy. RPE65 is a gene that has a prominent function in the development of a protein that is essential for the formation of images in the brain. Mutations in RPE65 can lead to retinitis pigmentosa (RP) and cone-rod dystrophy, which leads to blindness (Morimura et al. 1998).
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Published in Carl W. Hall, Laws and Models, 2018
where Io = intensity of incident beam R = reflectivity of the surfaces of the plate T = transmissivity = phase difference between directly transmitted light and light that is once reflected from the two internal surfaces of the plates Keywords: beam, light, plates, reflectivity, transmissivity AIRY, Sir George Biddell, 1801-1892, English astronomer and mathematician Source: Ballentyne, D. W. G. and Lovett, D. R. 1980. See also BEER; LAMBERT; REFLECTION ALBEDO LAW A perfect diffuse reflection obeys Lambert cosine law in which the surface brightness of the reflecting surface is proportional to the cosine of the angle of incidence and is independent of the angle of reflection. Keywords: brightness, cosine, diffuse, incidence, reflection Sources: Gray, H. J. and Isaacs, A. 1975; Michels, W. C. 1961. See also LAMBERT ALBITE LAW--SEE TWIN LAW ALEXANDER LAW Involuntary rapid movement of the eyeball is enhanced if the gaze is turned. A nystagmus (a rapid involuntary oscillation of the eyeballs), produced either by rotation or thermally, can be accentuated by moving the eyes in the direction of the jerky component of the nystagmus, the rapid return movement of the eyes in a direction opposite to the initial, slow movement. Keywords: eye, movement ALEXANDER, Gustav, 1873-1932, Austrian doctor Sources: Landau, S. I. 1986; Zusne, L. 1984. ALFVN NUMBER (Al) OR ALFVN SPEED OR ALFVN GROUP A dimensionless group that represents the propagation of acoustic waves in presence of a magnetic field: Al = v L ( )1/2 B–1/2 where v L B = = = = = velocity of flow length density permeability magnetic flux density
Vestibular and Related Oculomotor Disorders
Published in Anthony N. Nicholson, The Neurosciences and the Practice of Aviation Medicine, 2017
Nicholas J. Cutfield, Adolfo M. Bronstein
Pursuit and saccades in the horizontal and vertical planes should be elicited, and the horizontal vestibulo-ocular reflex checked by the doll’s manoeuvre and by head impulse testing, and then by suppression of the reflex. The Hallpike manoeuvre (Cawthorne et al., 1956) checks for positioning nystagmus and must be carried out in all patients with dizziness, vertigo and unsteadiness (see Benign Paroxysmal Positional Vertigo). Peripheral vestibular disorders have an abnormal vestibulo-ocular reflex, but other eye movements are normal. Central disorders of eye movements may produce any combination of pathological nystagmus, impaired visual pursuit, suppression of the vestibulo-ocular reflex and saccades. Neurological examination in the context of dizziness and imbalance should include inspection of the gait, Romberg’s test and the postural reflexes, as well as eliciting the possibility of cerebellar signs such as limb ataxia by finger–nose testing. Postural blood pressure recording is usually useful, as orthostatic hypotension can coexist with vestibular pathology.
The effects of breath alcohol concentration on postural control
Published in Traffic Injury Prevention, 2018
Nystagmus is an involuntary jerking of the eyeball that can occur for a variety of reasons (Dell'Osso 1989), including pathology, trauma, vestibular disturbances, and other neural disorders. Within the impaired driving context, however, HGN specifically refers to a lateral jerking of the eyeball affected by alcohol, certain nervous system depressants, inhalants, and dissociative anesthetics, including phencyclidine. The HGN test consists of 6 clues, 3 for each eye: Lack of smooth pursuit, maximum deviation, and angle of onset (NHTSA 1999). Four out of 6 possible clues indicate impairment. The WAT test requires a person to assume a heel-to-toe position on a real or imaginary line, arms at the sides, and to listen while instructions are given. The person is then required to make 9 heel-to-toe steps along the line, turn around keeping one foot on the line, and return with another 9 heel-to-toe steps. Two out of 8 possible clues indicate impairment. The OLS test requires a person to stand, feet together, and arms at the sides. The person is then required to raise one leg up about 6 inches (15 cm) off the ground, foot parallel to the ground, toes pointed forward, and count aloud for 30 s. Two out of 4 possible clues indicate impairment. The WAT and OLS are commonly referred to as divided attention tests. In both tests, the person is asked to maintain equilibrium while receiving fairly complex instructions. It is the combination of physical and cognitive demands that makes the tests sensitive to the effects of alcohol (Fiorentino 2015).
Survey regarding the 0.05 blood alcohol concentration limit for driving in the United States
Published in Traffic Injury Prevention, 2018
Dary D. Fiorentino, Brian D. Martin
Nystagmus is an involuntary jerking of the eyeball that occurs when there is a disturbance of the vestibular system (NHTSA 1999). Nystagmus is a complex phenomenon that can occur for a variety of reasons (Dell'Osso 1989). Within the impaired driving context, HGN specifically refers to a lateral jerking of the eyeball affected by alcohol, certain nervous system depressants, inhalants, and phencyclidine (NHTSA 1999). The HGN test is composed of the following 6 clues (3 for each eye): “(1) [l]ack of smooth pursuit, (2) distinct nystagmus at maximum deviation, [and] (3) onset of nystagmus before 45 degrees” (Rubenzer 2008, p. 295). Four out of the 6 possible clues indicate impairment.
Measuring Visual Fatigue and Cognitive Load via Eye Tracking while Learning with Virtual Reality Head-Mounted Displays: A Review
Published in International Journal of Human–Computer Interaction, 2022
Alexis D. Souchet, Stéphanie Philippe, Domitile Lourdeaux, Laure Leroy
We note that mainly six features are usually used to measure cognitive load (Zagermann et al., 2016) and visual fatigue (J. Iskander et al., 2018). We are presenting them all, notwithstanding the experimental conditions or creators’ purpose: Blinks: this metric has been identified for several years to measure fatigue (Stern et al., 1994). Martins and Carvalho (2015) meta-analysis focuses on blinking as a metric of fatigue (including visual fatigue) and mental load. However, the authors report that at least three environmental factors influence blinking: temperature, relative humidity, and lighting conditions of the room where assessment takes place. The subject’s activity during assessment (stimuli, interactions) has also been described to impact the frequency of blinks (Gebrehiwot et al., 2015). According to Lenskiy and Paprocki (2016), a reading task reduces the number of blinks compared to when subjects rest. The movements’ velocity in a scene with stereoscopy decreases the number of blinks and visual comfort (Li et al., 2013). This indicates that blinking is attention-related. Simultaneously, blinking has been identified as an indicator of dopamine activity related to cognitive activity in humans as early as five months of age (Bacher et al., 2017).Pupil diameter: this feature, dilation most often, can be associated with attention and cognitive process (John et al., 2018). However, the environmental variables impacting pupil diameter variation are vast (Peinkhofer et al., 2019): scene colors, brightness, and movement.Fixation frequency: this feature corresponds to when a gaze fixation stays on a particular object. It is correlated with cognitive load (Zu et al., 2017): fixation time tends to increase with high cognitive load.Point of gaze (POG) accuracy: this feature relates to the fixation time and represents the distance between the fixed point and a defined target during each fixation. In the event of fatigue, the accuracy of the POG should decrease. This parameter can thus be used to assess visual fatigue (Urvoy et al., 2013).Nystagmus: this feature is defined as the “involuntary oscillation movement of the eyeball following disturbance of the coordination of the eye muscles” (Al-Zubidi et al., 2018). These oscillations increase with visual fatigue and, therefore, can be used to assess visual fatigue.Saccades: this feature consists of measuring “quick eye shifts that normally place the line of sight on the desired target in a single smooth movement” (Schut et al., 2017). Saccades assessment is used to assess visual fatigue (Iatsun et al., 2013) and cognitive load (Zagermann et al., 2016).