Early detection and prevention of vision defects
Micha de Winter, Mariëlle Balledux, José de Mare, Ruud Burgmeijer in Screening in Child Health Care, 2018
Depending on the age group, prevalence figures vary between 1.2% and 6.4% (Holt 1974, Bayley et al. 1974, Taylor 1987, National Counselling Committee for Early Detection of Vision Defects (LBC-VOV) 1988, Feldmann et al. 1988). In the majority of cases, amblyopia is found together with manifest squint (so that it is easy to recognize), but in some 30% the eyes are (apparently) straight (LBC-VOV 1988) Untreated amblyopia may lead to, inter alia, disturbance of central fixation on the retina, disruption of the capacity to see depth and severely decreased acuity in the suppressed eye. Refractive errors are disturbances of the optical system of the eye, such that a sharp image is not produced precisely on the retina. Little can be said about prevalence, because practically everybody has some refractive error; according to Hall (1989) the decision as to when a refractive error should be regarded as abnormal depends on clinical expertise and personal judgment.
Basic science, investigations and lasers
Mostafa Khalil, Omar Kouli in The Duke Elder Exam of Ophthalmology, 2019
Vision 2020 was established by the International Agency of the Prevention of Blindness (5) and supported by the World Health Organization (WHO) (6) to eliminate preventable causes of blindness by the year 2020. The following conditions are in their current objectives: Cataract: The most common cause of blindness in the world.Trachoma: The most common cause of infectious blindness.Onchocerciasis: The second most common cause of infectious blindness.Refractive errors: The most common cause of visual impairment.Childhood blindness: Vitamin A deficiency (the most common cause of nutritional blindness in Africa), measles, retinopathy of prematurity (ROP) and cataract.
Examination of the Nervous System
John W. Scadding, Nicholas A. Losseff in Clinical Neurology, 2011
The normal distance acuity is 6/6, the numerator representing the distance of the patient from the chart (6 m) and the denominator the distance in metres at which a normal person is able to read that line (Figure 3.1). Decreasing acuity is recorded as 6/9, 6/12, 6/18, 6/24, 6/36, 6/60, and then as the ability to count fingers, perceive hand movements or, finally, perceive light. Near acuity is tested by asking the patient to read standardized test type, again correcting any refractive error. Near vision is a less accurate assessment of acuity. Most patients with a VA of 6/18 for distance can read N5 or N6 size test type. For driving in the UK, it is necessary to read a number plate at 75 feet (22.9 m), which is a VA between 6/9 and 6/12.
Neuro-Ophthalmic Literature Review
Published in Neuro-Ophthalmology, 2018
David Bellows, Noel Chan, John Chen, Hui-Chen Cheng, Peter MacIntosh, John H. Pula, Michael Vaphiades, Konrad P. Weber, Sui Wong
Noonan syndrome (NS) is an autosomal dominant disorder with variable phenotype, including short stature, congenital heart defects, and ophthalmological abnormalities. Different mutations in coding genes leading to dysregulation of the Ras/mitogen-activated protein kinase pathway can cause NS. The authors describe a retrospective review of 105 NS patients in the Netherlands. Sixty eight were under the age of 18 years. The primary outcome of the study was presence of ocular abnormalities in NS population. Seven patients were visually impaired, mainly attributable to binocular optic nerve abnormalities and manifest nystagmus related to RAF1, SHOC2, and KRAS gene mutations. Twenty-eight patients had amblyopia. Refractive errors included myopia, hyperopia, and astigmatism. Ten patients had high refractive errors.
Clinical Practice Guidelines for the Detection and Treatment of Amblyopia: A Systematic Literature Review
Published in Journal of Binocular Vision and Ocular Motility, 2022
Gareth Lingham, Myra B. McGuinness, Sare Safi, Iris Gordon, Jennifer R. Evans, Stuart Keel
Screening programs are intended to detect individuals at high risk of amblyopia among a healthy population to facilitate earlier access to treatment and vary greatly in diagnostic accuracy.17,18 In areas of low amblyopia prevalence, high rates of false positives following vision screening decrease confidence in screening programs, and therefore the type of screening program (which is increasingly instrument-based in North America) must be taken into account when considering recommendations for implemention.18 In comparison, comprehensive eye examinations are intended to diagnose/rule out ophthalmic conditions and assess refractive error. One or more in-person comprehensive eye examinations by an appropriately trained professional may improve detection rates and should reduce reliance on screening programs. However, comprehensive exams are more costly to individuals and the healthcare system, require a greater trained workforce capacity, and often place an additional level of responsibility on parents compared to that required for screening programs.
Sub-chronic and chronic toxicity evaluation of 7-methylxanthine: a new molecule for the treatment of myopia
Published in Drug and Chemical Toxicology, 2022
Harjeet Singh, Harmanpreet Singh, Nikhil Shri Sahajpal, Surinder Paul, Inderjit Kaur, Subheet Kumar Jain
Myopia is a common and complex visual disability refractive error, also known as nearsightedness. In definition, a refractive error of greater than 0.25 or 0.50 diopters is defined as myopia (Saw et al. 1996). Myopia, greater than 6 diopter causes blindness complications which may be responsible for the other irreversible vision-threatening conditions viz. glaucoma, retinal detachment, macular degeneration, etc. (Saw et al. 2002, Numa et al. 2018). It is the most prevalent refractive error with prevalence varying across different regions and races due to changes in the lifestyle, competitive educational system, near work activities (watching television, using computers, and reading) and genetic factor (Parveen et al. 2015, Williams et al. 2015, Hsu et al. 2016, Guo et al. 2016). East Asian population has a higher prevalence rate of myopia in comparison to the western population and it is more prevalent in industrialized countries (Saw 2006). According to the world health organization report, the prevalence of myopia in 2020 was estimated to be 22%, and the data indicate that myopia will affect 52% of people in the world by 2050 (WHO 2019. https://www.who.int/blindness/causes/MyopiaReportforWeb.pdf).
Related Knowledge Centers
- Astigmatism
- Blurred Vision
- Cornea
- Diplopia
- Eye
- Presbyopia
- Retina
- Focus
- Near-Sightedness
- Far-Sightedness