prismatic lenses

PURPOSE: To examine the time course of the reduction in central corneal clearance and horizontal and vertical lens translation (decentration) during miniscleral contact lens wear and the theoretical influence upon the optics of the post-lens tear layer. METHODS: Repeated high-resolution OCT images were captured over an 8h period of miniscleral contact lens wear (using a rotationally symmetric 16.5mm diameter lens) in 15 young, healthy participants with normal corneae...

PURPOSE: Horizontal peripheral prisms for hemianopia provide field expansion above and below the horizontal meridian; however, there is a vertical gap leaving the central area (important for driving) without expansion. In the oblique design, tilting the bases of both prism segments toward the horizontal meridian moves the field expansion area vertically and centrally (closing the central gap) while the prisms remain in the peripheral location. However, tilting the prisms results also in a reduction of the lateral field expansion...

PRIMARY OBJECTIVE: To examine the effectiveness of neutralizing prismatic lenses for reduction of headache, dizziness and anxiety in patients with persistent post-concussive symptoms and vertical heterophoria (VH). BACKGROUND: Approximately 5-10% of patients with traumatic brain injury (TBI) develop persistent post-concussive symptoms. Many rehabilitation/treatment modalities are tried, but are largely unsuccessful, indicating a need for more effective treatment...

Sensorimotor plasticity allows us to maintain an efficient motor behavior in reaction to environmental changes. One of the classical models for the study of sensorimotor plasticity is prism adaptation. It consists of pointing to visual targets while wearing prismatic lenses that shift the visual field laterally. The conditions of the development of the plasticity and the sensorimotor after-effects have been extensively studied for more than a century. However, the interest taken in this phenomenon was considerably increased since the demonstration of neglect rehabilitation following prism adaptation by Rossetti et al...

The physiological regulation of skin temperature can be modulated not only by autonomic brain regions, but also by a network of higher-level cortical areas involved in the maintenance of a coherent representation of the body. In this study we assessed in healthy participants if the sensorimotor changes taking place during motor adaptation to the lateral displacement of the visual scene induced by wearing prismatic lenses (prism adaptation, PA), and the aftereffects, after prisms' removal, on the ability to process spatial coordinates, were associated with skin temperature regulation changes...

The susceptibility to hypnosis, which can be measured by scales, is not merely a cognitive trait. In fact, it is associated with a number of physiological correlates in the ordinary state of consciousness and in the absence of suggestions. The hypnotizability-related differences observed in sensorimotor integration suggested a major role of the cerebellum in the peculiar performance of healthy subjects with high scores of hypnotic susceptibility (highs). In order to provide behavioral evidence of this hypothesis, we submitted 20 highs and 21 low hypnotizable participants (lows) to the classical cerebellar Prism Adaptation Test (PAT)...

We have designed an intraocular telescope for the posterior chamber of the human eye of patients with age related macular degeneration. The basic design is composed of two decentered high optical power lenses ( + 66D and -66D) inducing a 3° prismatic effect to project a magnified central field of view into a healthier location off the central fovea. Aspheric surfaces were used to ensure a compromise between good optical quality and high tolerance to the final axial position of both lenses after surgery. With this particular design, the telescope affords an extended range of depth of focus, high tolerance to different axial lengths of the eye and robustness against typical values of astigmatism and higher order aberrations...

PURPOSE: To evaluate the safety and efficacy of the iol-AMD technology (London Eye Hospital Pharma, London, UK), which includes two injectable, hydrophobic acrylic intraocular lenses (IOLs) in a pilot study of patients diagnosed as having cataract and dry age-related macular degeneration. METHODS: The cataract surgery and IOL implantation were performed after a preoperative evaluation using the iolAMD simulator in eyes with bilateral intermediate dry age-related macular degeneration...

The management of ocular motor palsies first requires careful determination of the etiology. Possibilities include ischemia, inflammation, infection, trauma, compression, or congenital. Prognosis for recovery varies greatly between etiologies; hence, determination of the underlying process is crucial in the short- and long-term management of these patients. Naturally, our ultimate goal is to improve visual function as much as possible. A guiding principle in the initial management of ocular motor palsies is to improve patient comfort and visual function by eliminating diplopia in primary position while clinically observing the patient for improvement or stability...

Binocular diplopia is a debilitating visual symptom requiring immediate intervention for symptomatic control, whether or not definitive treatment is eventually possible. Where prismatic correction is infeasible, the current standard is occlusion, either by a patch or an opaque contact lens. In eliminating one problem-diplopia-occlusive techniques invariably create another: reduced peripheral vision. Crucially, this is often unnecessary, for the reduced spatial resolution in the periphery limits its contribution to the perception of diplopia...

It has been proposed that motor adaptation depends on at least two learning systems, one that learns fast but with poor retention and another that learns slowly but with better retention (Smith MA, Ghazizadeh A, Shadmehr R. PLoS Biol 4: e179, 2006). This two-state model has been shown to account for a range of behavior in the force field adaptation task. In the present study, we examined whether such a two-state model could also account for behavior arising from adaptation to a prismatic displacement of the visual field...

PURPOSE: Recently, a number of lens mappers have become available for measuring the detailed optical properties of progressive addition lenses (PALs). The goal of this study was to compare the results obtained from several different lens mappers for a range of different lenses. METHODS: The optical power maps of six lenses-two single-vision lenses, a parallel-sided slide, a flat prism, and two progressive lenses-were measured using four different lens mappers: the Dual Lens Mapper, the Nimo TR4005, the Rotlex Class Plus, and the Visionix VM2500...

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Patients with hemispatial neglect ('neglect') following a brain lesion show difficulty responding or orienting to objects and events on the left side of space. Substantial evidence supports the use of a sensorimotor training technique called prism adaptation as a treatment for neglect. Reaching for visual targets viewed through prismatic lenses that induce a rightward shift in the visual image results in a leftward recalibration of reaching movements that is accompanied by a reduction of symptoms in patients with neglect...

PURPOSE: An accurate vestibulo-ocular reflex is important for gaze stability, and is adaptable through modification, based on stable and repeated vestibular and visual feedback. The optical power of eye glasses changes the ocular rotation needed to view an object due to the prismatic effect. Depending on the diopter of a lens, eyes have to rotate through fewer or more degrees to correct for refractive change. We aim to determine how multifocal lenses, such as progressives, affect needed ocular rotation and ocular gain based on location of the lens in which an object is viewed...

PURPOSE: To perform a pilot study of a new in-the-bag Fresnel prism intraocular lens (IOL) designed to deviate the image from diseased to healthy retina in eyes with bilateral age-related macular degeneration (AMD). SETTING: Anterior segment subspeciality practice, Pretoria, South Africa. DESIGN: Prospective nonmasked trial. METHOD: Cataract surgery and unilateral implantation of the prismatic IOL were performed in patients with bilateral AMD and cataract...

BACKGROUND: Multifocal glasses (bifocals, trifocals, and progressives) increase the risk of falling in elderly people, but how they do so is unclear. To explain why glasses with progressive addition lenses increase the risk of falls and whether this can be attributed to false projection, this study aimed to 1) map the prismatic displacement of a progressive lens, and 2) test whether this displacement impaired reaction time and accuracy. METHODS: The reaction times of healthy ≥75-year-olds (31 participants) were measured when grasping for a bar and touching a black line...

Hemispatial neglect ('neglect') is a disabling condition that can follow damage to the right side of the brain, in which patients show difficulty in responding to or orienting towards objects and events that occur on the left side of space. Symptoms of neglect can manifest in both space- and object-based frames of reference. Although patients can show a combination of these two forms of neglect, they are considered separable and have distinct neurological bases. In recent years considerable evidence has emerged to demonstrate that spatial symptoms of neglect can be reduced by an intervention called prism adaptation...

IMPORTANCE: Myopia is a significant public health problem, making it important to determine whether a bifocal spectacle treatment involving near prism slows myopia progression in children. OBJECTIVE: To determine whether bifocal and prismatic bifocal spectacles control myopia in children with high rates of myopia progression and to assess whether the treatment effect is dependent on the lag of accommodation and/or near phoria status. DESIGN, SETTING, AND PARTICIPANTS: This 3-year randomized clinical trial was conducted in a private practice...

BACKGROUND: The accuracy and precision of any instrument should not be taken for granted. While there is an international standard for checking focimeters, there is no report of any study on their performance. METHOD: A sample set of 51 focimeters (11 brands), were used to measure the spherical power of a set of lenses and the prismatic power of two lenses complying with ISO 9342-1:2005 and other calibrated prismatic lenses and the spherical power of some grey filters...