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Clinical & Experimental Optometry Jan 2020Stand magnifiers are still one of the most commonly prescribed classes of low vision devices. Their performance can be difficult to understand because stand magnifiers... (Review)
Review
Stand magnifiers are still one of the most commonly prescribed classes of low vision devices. Their performance can be difficult to understand because stand magnifiers usually do not give an image at infinity. This review summarises the methods of describing image enlargement for stand magnifiers, emphasising their relationship to equivalent viewing distance (EVD). This is done in terms of the underlying optical equations, and measurement methods, and methods of prescribing. In the past, methods of determining EVD have been somewhat indirect, requiring accurate measurement of lens power, and image position. The use of digital photography provides an alternative, more direct, simpler method of determining EVD, which can be accomplished in-office. This method is described and it is demonstrated how it gives comparable results to older methods with small, clinically non-meaningful differences, that may be due to differences in image distance reference planes. Describing the performance of stand magnifiers in terms of their dioptric power, or in terms of 'nominal magnification' or 'trade magnification', is imprecise and misleading. It is better to use indices such as equivalent viewing power and EVD, which take into account the magnifier dioptric power, the image position of the magnifier and the distance a patient is from the magnifier. While EVD is a useful index for prescribing stand magnifiers, manufacturers do not always provide sufficient technical details to determine EVD for their stand magnifiers, and available tables of EVDs are more than a decade old and are likely to need updating. Photographic comparison provides a method for determining EVD, and this method can also be applied to other low vision devices.
Topics: Equipment Design; Humans; Optics and Photonics; Prescriptions; Reading; Sensory Aids; Vision, Low
PubMed: 31429123
DOI: 10.1111/cxo.12948 -
Indian Journal of Ophthalmology Feb 2021The current practice for low vision management in India exclusively focuses on clinical aspects without much of the rehabilitation components. While making all efforts... (Review)
Review
The current practice for low vision management in India exclusively focuses on clinical aspects without much of the rehabilitation components. While making all efforts to improve independent living skills, daily living activities, and quality of life as a whole for people living visual disabilities, vision rehabilitation is an indispensable component. There is no single appropriate low vision and rehabilitation model implementable at health care institutions in the country to cover these fundamental aspects of a visually impaired individual. We did a literature review to know the existing practices of low vision and various disability models. The purpose of the review is to discern any pitfalls and shortcomings in managing visually disabled in India and to underpin the credibility and feasibility as well as suitability of the developed model. The review was done using search key terms low vision, current practices, visual disability, disability models, vision rehabilitation, and service delivery. Therefore, the article discusses the development of an inclusive low vision management model name as "Clinico-Social Model", which we consider the most appropriate for the best management of people with vision loss. The primary aim of this model is to provide both clinical and vision rehabilitation components of management for people with visual disabilities. Such an approach is likely to have the potential to improve the quality of life of people with vision loss and can provide practical guide to eye care managers across India. Given the specific context in the current practices of low vision in India, it is desirable to design a similar model to care for the visually disabled.
Topics: Disabled Persons; Humans; India; Quality of Life; Vision, Low; Visually Impaired Persons
PubMed: 33463601
DOI: 10.4103/ijo.IJO_236_20 -
Optometry and Vision Science : Official... Aug 2022Digital reading devices have become increasingly popular among people with low vision. Because displays come in many sizes ranging from smart watches to large desktop...
SIGNIFICANCE
Digital reading devices have become increasingly popular among people with low vision. Because displays come in many sizes ranging from smart watches to large desktop computer displays, it is important to have principles to guide people with low vision in selecting suitable displays for reading.
PURPOSE
The selection of effective digital displays for reading by people with low vision focuses attention on the interacting effects of print size, display size, font, visual acuity, and reading distance. This technical report aims to provide principles for identifying the minimum size of digital displays required for fluent reading by people with low vision.
METHODS
We emphasize two critical factors in selecting an appropriate reading display: angular print size, which should exceed the individual's critical print size, and display size, which should allow at least 13 characters to be presented on each line. Our approach considers a low-vision individual's acuity and preferences for viewing distance and fonts.
RESULTS
Through an illustrative example, we demonstrate how our approach can be used to determine display size for a low-vision individual with 20/200 acuity and central field loss who wants to read at 30-cm viewing distance with the Times Roman font. We have developed a web application based on our recommended approach to provide easy access to our algorithm.
CONCLUSIONS
We provide a procedure to guide the selection of appropriate displays for a wide range of acuities. Our approach can help clinicians in making recommendations for their patients, digital product designers in developing more accessible devices, and low-vision individuals in selecting digital displays for reading.
Topics: Humans; Reading; Vision Disorders; Vision Tests; Vision, Low; Visual Acuity
PubMed: 35731508
DOI: 10.1097/OPX.0000000000001919 -
The Cochrane Database of Systematic... Mar 2015Low vision in childhood is a significant barrier to learning and development, particularly for reading and education. Optical low vision aids may be used to maximise the... (Review)
Review
BACKGROUND
Low vision in childhood is a significant barrier to learning and development, particularly for reading and education. Optical low vision aids may be used to maximise the child's functional vision. The World Health Organization (WHO) has previously highlighted the importance of the use of low vision aids in managing children with visual impairment across the world.
OBJECTIVES
To assess the effect of optical low vision aids on reading in children and young people with low vision.
SEARCH METHODS
We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2014, Issue 12), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to January 2015), EMBASE (January 1980 to January 2015), the Health Technology Assessment Programme (HTA) (www.hta.ac.uk/), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 8 January 2015.We also used manual searching to check the references listed in retrieved articles. Manufacturers of low vision aids were contacted to request any information about studies or research regarding their products.
SELECTION CRITERIA
We planned to include randomised controlled trials (RCTs) and quasi-RCTs where any optical low vision aid was compared to standard refractive correction in children and young people aged between 5 and 16 years of age with low vision as defined by the WHO. We planned to include within-person design studies where the order of presentation of devices was randomised.
DATA COLLECTION AND ANALYSIS
Two authors independently reviewed the search results for eligibility .
MAIN RESULTS
No studies met the inclusion criteria for this review.
AUTHORS' CONCLUSIONS
There is a lack of good quality evidence regarding the use of optical low vision aids in children and young people. As such, no implications for practice can be drawn. We believe future research should include functional outcome measures such as reading speed, accuracy and comprehension, as well as the effect of low vision aids on quality of life, in order to truly assess and compare the effect of these devices on a child's life and development.
Topics: Humans; Optical Devices; Reading; Vision, Low
PubMed: 25738963
DOI: 10.1002/14651858.CD010987.pub2 -
Acta Psychologica Feb 2023Patients with low vision are generally recommended to use the same fonts as individuals with normal vision. However, we are yet to fully understand whether stroke width...
PURPOSE
Patients with low vision are generally recommended to use the same fonts as individuals with normal vision. However, we are yet to fully understand whether stroke width and serifs (small ornamentations at stroke endings) can increase readability. This study's purpose was to characterize the interaction between two factors (end-of-stroke and stroke width) in a well-defined and homogenous group of patients with low vision.
METHODS
Font legibility was assessed by measuring word identification performance of 19 patients with low vision (autosomal dominant optic atrophy [ADOA] with a best-corrected average visual acuity 20/110) and a two-interval, forced-choice task was implemented. Word stimuli were presented with four different fonts designed to isolate the stylistic features of serif and stroke width.
RESULTS
Font-size threshold and sensitivity data revealed that using a single measure (i.e., font-size threshold) is insufficient for detecting significant effects but triangulation is possible when combined with signal detection theory. Specifically, low stroke contrast (smaller variation in stroke width) yielded significantly lower thresholds and higher sensitivity when a font contained serifs (331 points; d' = 1.47) relative to no serifs (345 points; d' = 1.15), E(μ - μ) = -14 points, 95 % Cr. I. = [-24, -5], P(δ > 0) = 0.99 and E(μ - μ) = 0.32, 95 % Cr. I. = [0.16, 0.49], P(δ > 0) = 0.99.
CONCLUSION
In people with low visual acuity caused by ADOA, the combination of serifs and a uniform stroke width resulted in better text legibility than other combinations of uniform/variable stroke widths and presence/absence of serifs.
Topics: Humans; Vision, Low; Form Perception; Reading; Comprehension; Research Design; Stroke
PubMed: 36563495
DOI: 10.1016/j.actpsy.2022.103810 -
Optometry and Vision Science : Official... Sep 2012
Topics: Aged; Biomedical Research; Humans; Middle Aged; Optometry; Periodicals as Topic; Vision, Low
PubMed: 22926111
DOI: 10.1097/OPX.0b013e31826ba359 -
The Cochrane Database of Systematic... May 2010Orientation and mobility (O&M) training is provided to people who are visually impaired to help them maintain travel independence. It teaches them new orientation and... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Orientation and mobility (O&M) training is provided to people who are visually impaired to help them maintain travel independence. It teaches them new orientation and mobility skills to compensate for reduced visual information.
OBJECTIVES
The objective of this review was to assess the effects of O&M training, with or without associated devices, for adults with low vision.
SEARCH STRATEGY
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library, 2010, Issue 3), MEDLINE (January 1950 to March 2010), EMBASE (January 1980 to March 2010), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to March 2010), System for Information on Grey Literature in Europe (OpenSIGLE) (March 2010), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) (March 2010), ClinicalTrials.gov (http://clinicaltrials.gov) (March 2010), ZETOC (March 2010) and the reference lists of retrieved articles. There were no language or date restrictions in the search for trials. The electronic databases were last searched on 31 March 2010.
SELECTION CRITERIA
We planned to include randomised or quasi-randomised trials comparing O&M training with no training in adults with low vision.
DATA COLLECTION AND ANALYSIS
Two authors independently assessed the search results for eligibility, evaluated study quality and extracted the data.
MAIN RESULTS
Two small studies satisfied the inclusion criteria. They were consecutive phases of development of the same training curriculum and assessment tool. The intervention was administered by a volunteer on the basis of written and oral instruction. In both studies the randomisation technique was inadequate, being based on alternation, and masking was not achieved. Training had no effect in the first study but tended to be beneficial in the second but not to a statistically significant extent. Reasons for differences between studies may have been: the high scores obtained in the first study, suggestive of little need for training and small room for further improvement (a ceiling effect), and the refinement of the curriculum allowing better tailoring to patients' specific needs and characteristics, in the second study.
AUTHORS' CONCLUSIONS
The review found two small quasi-randomised trials with similar methods, comparing training to physical exercise and assessing O&M physical performance by means of a volunteer or a professional, which were unable to demonstrate a difference. Therefore, there is little evidence on which type of O&M training is better for people with low vision who have specific characteristics and needs. Orientation and mobility instructors and scientists should plan randomised controlled trials (RCTs) to compare the effectiveness of different types of O&M training. A consensus is needed on the adoption of standard measurement instruments of mobility performance which are proven to be reliable and sensitive to the diverse mobility needs of people with low vision. For this purpose, questionnaires and performance-based tests may represent different tools that explore people with low vision's subjective experience or their objective functioning, respectively. In fact, it has to be observed that low vision rehabilitation research is increasingly shifting towards the use of quality of life questionnaires as an outcome measure, sometimes with the aim to study complex and multidisciplinary interventions including different types of education and support, of which O&M can be a component. An example of this is an ongoing cluster RCT conducted by Zijlstra et al. in The Netherlands. This trial is designed to compare standardised O&M training with usual O&M care not only for its effectiveness, but also its applicability and acceptability. This study adopts validated questionnaires for patients' subjective assessment of performance during activities of daily living. As performance assessment does not need to be made by an O&M trainer, this allows for masking of assessors and a patient-centred outcome measure.
Topics: Adult; Exercise Therapy; Humans; Locomotion; Orientation; Randomized Controlled Trials as Topic; Travel; Vision, Low
PubMed: 20464725
DOI: 10.1002/14651858.CD003925.pub3 -
Optometry and Vision Science : Official... Nov 2022Understanding longitudinal changes in why individuals frequent low-vision clinics is crucial for ensuring that patient care keeps current with changing technology and...
SIGNIFICANCE
Understanding longitudinal changes in why individuals frequent low-vision clinics is crucial for ensuring that patient care keeps current with changing technology and changing lifestyles. Among other findings, our results suggest that reading remains a prevailing patient complaint, with shifting priorities toward technology-related topics.
PURPOSE
This study aimed to understand changes in patient priorities and patient care in low vision over the past decade.
METHODS
We conducted a retrospective study of examination records (2009 to 2019, 3470 examinations) from two U.S. low-vision clinics. Automated word searches summarized two properties of the records: topics discussed during the case history and types of rehabilitative devices assessed. Logistic regression was used to model the effects of examination year, patient age, patient sex, and level of visual impairment.
RESULTS
Collapsing across all years, the most common topic discussed was reading (78%), followed by light-related topics (71%) and technology (59%). Whereas the odds of discussing reading trended downward over the decade (odds ratio, 0.57; P = .03), technology, social interaction, mobility, and driving trended upward (odds ratios, 4.53, 3.31, 2.71, and 1.95; all P 's < 0.001). The most frequently assessed devices were tinted lenses (95%). Over time, video magnifier and spectacle assessments trended downward (odds ratios, 0.64 and 0.72; P = .004, 0.04), whereas assessments of other optical aids increased. The data indicate several consistent differences among patient demographics.
CONCLUSIONS
Reading is likely to remain a prevailing patient complaint, but an increase in technology-related topics suggests shifting priorities, particularly in younger demographics. "Low-tech" optical aids have remained prominent in low-vision care even as "high-tech" assistive devices in the marketplace continue to advance.
Topics: Humans; Vision, Low; Retrospective Studies; Acquired Immunodeficiency Syndrome; Visual Acuity; Eyeglasses; Reading
PubMed: 36301592
DOI: 10.1097/OPX.0000000000001953 -
The British Journal of Ophthalmology Apr 1996
Topics: Humans; Medical Audit; Orthoptics; Vision, Low
PubMed: 8703898
DOI: 10.1136/bjo.80.4.380-b -
Vision Research Sep 2007It is thought by cognitive scientists and typographers alike, that lower-case text is more legible than upper-case. Yet lower-case letters are, on average, smaller in...
It is thought by cognitive scientists and typographers alike, that lower-case text is more legible than upper-case. Yet lower-case letters are, on average, smaller in height and width than upper-case characters, which suggests an upper-case advantage. Using a single unaltered font and all upper-, all lower-, and mixed-case text, we assessed size thresholds for words and random strings, and reading speeds for text with normal and visually impaired participants. Lower-case thresholds were roughly 0.1 log unit higher than upper. Reading speeds were higher for upper- than for mixed-case text at sizes twice acuity size; at larger sizes, the upper-case advantage disappeared. Results suggest that upper-case is more legible than the other case styles, especially for visually-impaired readers, because smaller letter sizes can be used than with the other case styles, with no diminution of legibility.
Topics: Adult; Aged; Aged, 80 and over; Humans; Pattern Recognition, Visual; Printing; Reading; Sensory Thresholds; Time Factors; Vision, Low; Visual Acuity
PubMed: 17675131
DOI: 10.1016/j.visres.2007.06.010