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Non-Organic Vision Loss
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Ashwini Kini, Mangayarkarasi Thandampallayam Ajjeya, Padmaja Sudhakar
A similar test involves using polarized glasses, with one axis at 90° and the other at 180° in each lens and asking the patient to read a polarized eye chart with some letters perceptible only to one eye or the other.
Ophthalmic Injuries
Published in Ian Greaves, Keith Porter, Jeff Garner, Trauma Care Manual, 2021
Ian Greaves, Keith Porter, Jeff Garner
The most basic assessment of visual function is the visual acuity, which, ideally, is measured by asking the patient to read a distance eye chart or near eye chart. Visual acuity is recorded as a fraction, with the distance from the chart recorded as the numerator and the best line achieved on the chart as the denominator. The patient should wear his or her spectacles, but if they are not available (or vision is reduced), then a pinhole should be used to overcome any refractive error and some media opacity. The eyes are tested one at a time, with the other eye carefully occluded. Poor vision (unable to see any size letter at any distance) is recorded as the ability to count fingers, see hand movements or perceive light. Reduced vision that does not improve with a pinhole suggests pathology, whereas reduced vision that improves with pinhole indicates a refractive error.
The Effort to See
Published in John William Yee, The Neurological Treatment for Nearsightedness and Related Vision Problems, 2019
The eye chart is pegged at 20 ft during an eye test because light reaches the eye as parallel rays at that distance. Anything closer, the light rays diverges and the lens of your eye will have to bulge to shorten the focal length. A bulged or rounder crystalline lens converges the light rays so that the focal point will fall on the retina instead of behind it.
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
Visual, vestibular, and proprioceptive inputs are the three main sensory systems that play a key role in postural control during activities (Hansson, Beckman, and Hakansson, 2010). Vision impairment is most commonly detected by measuring a person’s visual acuity (VA) performance, which is a measure of the resolution of the eyes, particularly their ability to focus and distinguish high contrast objects (Sebag, Sadun, and Pierce, 2016). VA is important for avoiding small obstacles during ambulation (Lennie and Van Hemel, 2002), and is generally believed to help preventing tripping falls in older adults (Weerdesteyn, Nienhuis, and Duysens, 2005; Weerdesteyn et al., 2006). VA charts such as the Snellen eye chart has traditionally been the most commonly used clinical tool to assess visual function (Lennie and Van Hemel, 2002; Sebag, Sadun, and Pierce, 2016), and is typically an element of fall risk screening for older adults (Casey et al., 2017).
Determinants of fine manual dexterity in adolescents and young adults with Down’s syndrome
Published in International Journal of Developmental Disabilities, 2021
Chih-Chia (J.J.) Chen, Shannon D.R. Ringenbach
The vision and hearing assessments were also conducted. The vision was tested using a standard eye chart (i.e., Snellen) or a modified version which consists of E’s pointing in different directions for participants who could not recognize letters. The hearing was tested using an audiometer (the Maico Ma 25). If participants did not have at least 20/100 vision or was considered as hard of hearing, he/she would be also excluded in the study. The purpose of these assessments was to ensure they were able to understand the instructions and perform the test. In the current study, no participants were excluded. Based on our multiple resources and methods we believe that our sample is representative of the Down’s syndrome population. All protocols were approved by the Human Subjects Institutional Review Board of our University.
Orthoptic service survey in the UK and Ireland during the interim recovery period (summer 2020) of the COVID-19 pandemic
Published in Strabismus, 2021
Fiona J. Rowe, Lauren R. Hepworth, Claire Howard
The continuation of high numbers of teleconsultations brought remote testing of visual function to the forefront with concerns raised regarding the reliability of patient/parent-administered testing. A number of studies have been conducted during the pandemic specific to evaluating the reliability of home testing of visual acuity using software applications. Satgunam et al. conducted a validation study of smart phone acuity measurements in adult employees and reported that age and refractive error were important considerations when extending such studies to patient populations.21 In adult patients, results from smart phone eye chart app use corresponded well to results obtained with standard EDTRS acuity charts.22 One UK-based orthoptic study assessed parental ability to home test their child’s acuity comparing the Peek acuity and iSight Pro apps.23 Only 15 of 103 families agreed to home test with most finding it easy; however, some struggled. Thus, parental engagement and education must be addressed in future studies that evaluate home testing.