Definition Of Low Vision And Blindness Literature Reviews Example

Type of paper: Literature Review

Topic: Study, Disability, Education, Vision, Information, People, Prevalence, Impairment

Pages: 10

Words: 2750

Published: 2021/01/28

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Visual Impairments all around the World: A Review of the Literature

Abstract
Worldwide, there are more than 285 million people estimated to be visually impaired, according to the World Health Organization (2013). The author of this paper presents diverse research topics on visual impairment around the world such as common diagnosis and treatments, and the availability of opportunities in different countries. The author of this paper also discusses how education for people with visual disabilities varies by country.

Introduction

According to the World Health Organization (WHO), (2013), there are more than an estimated 285 million people worldwide with avisual impairment (Resnikoff, Pascolini, Etya’ale, Kocur, Pararajasegaram,Pokharel,&Mariotti, 2005). The National Federation of the Blind in 2011 stated there were more than 6,500,000 people with visual impairments living in the United States. Research has been done in several countries to identify the prevalence of various eye conditions. Also the quality of life for people with visual disabilities in different parts of the world has been investigated.
According to Resnikoff et al. (2002), their findings compiled from 2002 global data showed that there were more than 285 million people in the world with visual disabilities, and of that number, approximately 37 million were blind and 124 million had low vision. The most common cause of blindness was cataract, followed by glaucoma and age-related macular degeneration, and then corneal opacities, diabetic retinopathy and childhood blindness.
Studies were conducted in five continents regarding prevalence and causes of blindness and visual impairments in children and adults. The ability to collect data around the world has been attributed to a global information interchange and citing projected improvements in the area studied. There is little evidence that show the overall impacts of visual disability around the world.
Studies in Australia, Europe, and North America show the high incidence of low vision and blindness in people who are at least forty years of age and the more frequent reasons for the refractive errors (The Eye Disease Prevalence Research Group, 2004). Asia, Africa, and Latin America studies also show the incidence and cause of blindness and visual impairment in adults and children(Gilbert, Ellwein, & the Refractive Error Study in Children Study Group, 2008).Both studies showed that visual impairments resulting from low vision, refractive error, and blindness pose a grave health risk. While data has been compiled in both adults and children in population-based areas, more research is needed to determine leading causes and potentially produce preventative outcomes.

According to the definition provided on the website of the Lighthouse International (2014), low vision is the result of partial vision loss and cannot be corrected. A person with low vision has significant vision loss, reduced visual acuity or contrast sensitivity, an excessively obstructed field of vision or all the conditions at once. The most common symptoms are difficulty recognizing a familiar face, reading (letters appear distorted or incomplete), and seeing objects and potential hazards (e.g., identifying steps, walls, furniture, etc.).
Low vision is defined when visual acuity on the best eye with best correction is 20/70 or less. Individuals who suffer with low vision tend to have some vision capability but have difficulty being able to see things such as print, familiar faces, and objects in front of them (lighthouse International 2014). Legal blindness is defined when a person has central visual acuity of 20/200 or less in his or her better eye with correction.

Methods

In this literature review, a number of research papers were chosen taking into consideration its methods in gathering information about the participants. The articles were classified according to the methodology used and how the data was analyzed. The cross-sectional study conducted takes into account systematic and random sampling individuals aged more than 1 year old included evaluating the demographic data, eye complaints, eye exam, and history that correlate with visual acuity. Each of the subjects undergoes interview, visual acuity measurement, biometry, ophalmic examination, and biometry. The CSC was calculated for different levels of visual loss by person and by eye.
This paper discusses ten research studiesconductedin different continents. Each study was described in detail. These ten studies were chosen based on their birthplace and current place of residency. All studies took place between 1989 and 2013, and only articles written in English were included, despite their original language.
Researchers carried out, recorded and analyzed a national survey in their local place of origin. The main purpose of the study was to assess the prevalence and causes of vision loss in different countries and to discuss comparative concerns in all countries mentioned in the research papers. A population-based study was conducted in twelve different countries. Individuals aged 1 to 91 years participated in the research papers analyzed in this review of literature.

Prevalence and causes of low vision and blindness

The Eye Diseases Prevalence Research Group (2004) studied the occurrence of refractive errors like myopia and hyperopia in persons 40 years and older in Australia, Western Europe, and United States in 1985. Six study groups participated, Baltimore Survey in Maryland, Beaver Dam Eye Study in Wisconsin, the Proyecto VER in Arizona, Rotterdan Study in the Netherlands, Blue Mountains Eye Study in Australia, and the Melbourne Visual Impairment Project in Australia.
The results were obtained according to the following criteria: hyperopia, was defined as a refraction of +3 diopters (D) or more positive, myopia was defined as a refraction of -1 or more negative, and high myopia was defined as the subset of myopia of -1 D or less with a refraction of -5 D or more negative (The Eye Diseases Prevalence Research Group, 2004).
After data collection, results were analyzed by geographic location and race (white, black, and Hispanics).This analysis revealed predominance of hyperopia of +3 diopters or greater, myopia of -1 diopter or less, and myopia of -5 diopter or less in White persons, and then Blacks and Hispanics. According to the study, the predominance of hyperopia was observed to be progressively higher with increasing age. Another finding was the prevalence of myopia of -1 D or less inclined to be lower with a group with older people. The implications of the study showed that rates of prevalence of hyperopia and myopia varied among age, gender and race. The United States and Rotterdam showed nearly identical results, while Australian counterparts had noticeably lower results. (The Eye Disease Prevalence Research Group, 2004).
Another study, Vision Loss in Australia (Taylor,Keefee, Vu, Rochtchina, Mitchell, &Pezzullo, 2005), shows thatvision loss is considered a huge problem and it should gain attention among medical professionals. Visual impairment has not been a very popular subject in Australia, as few people would present an eye problem, or even a vision loss.
Between 1992 and 1996, Melbourne Visual Impairment Project and the Blue Mountains Eye Study were administered in Australia in order to identify the prevalence and cause of vision loss in that place. Around nine thousand persons from the Australian continent participated in the study.The urban study was conducted from 1992 to 1994, the nursing home and hostel study in 1995, and the rural study in 1996. The resultsindicated that 8,909 persons participated in the study. According to the data, it was possible to estimate that there were 50,600 Australians presenting uncorrected refractive error and uncorrectable blindness. The goal of the research was to identify the rate of visual impairments in Australia and to make projections for the future.
The study showed an exponential increase of vision loss according to age increase and the influence that the data will reveal on the uncorrected refractive error. This study was done with the purpose to raise awareness and improve the quality of service of public health (Taylor,et al.,2005).
The purpose of this research article was to report on the population-based data specifically on the prevalence and causes of visual impairment among children and adults in Botucatu, Brazil. The cross-sectional data was conducted to involve a random start point and a systematic sampling of the urban Brazilian population. In Brazil, the research article Prevalence and causes of visual impairment in a Brazilian population: The Botucatu Eye Study was conducted by Schellini,et al.,(2009),in a small city called Botucatu in the state of São Paulo.This study was carried out over a four month period by a team of five individuals.It involved 3,300 eligible participants aged 1 to 91, of which only 2,485 went through an ophthalmic examination. The sample size was generated based on the total population of Botucatu and a household size of 3.3 individuals. Of those who participated in the study, 5.2% of the participants were found presenting some type of visual impairment and 2.2% of them were considered legally blind (visual acuity 20/200 or less in the best eye). The main causes of low vision and blindness were uncorrected refractive errors, cataract, and retinal diseases. Findings showed that visual impairments were more rampant with each year of age. Interesting to note, of all the participants, no children were detected as having low vision, with the exception of one child with prevalent signs of blindness. The prevalence of blindness according to the authors of the study was perpetuated by different factors such as an increase in the life expectancy in the developing countries and the consequent increase in cataract and glaucoma.
The implications of these findings concluded that the prevalence of low vision and blindness are results of extended life expectancies and increased diagnosis of glaucoma and cataracts. However, leading causes of vision abnormalities as a whole in Brazil are from refractive error and cataracts. Macular degeneration and glaucoma were found to be the next most prevalent finding among participants.
Googin and O’Keefe (1991)did a small research project in the Republic of Ireland involving 172 children who were blind from 8 to 16 years of age. A full ophthalmic examination was provided to each patient and their family.Medical history was taken into consideration, as well as best-corrected visual acuity, ability to cooperate, and level of intelligence. Most of the participants (69 out of 172) acquired a visual impairment because of lesions that occurred before birth.The most frequent cases were optic nerve hypoplasia, optic atrophy, and cortical blindness. This study revealedthat almost 30% of the causes of blindness couldhave beenprevented. The main goal of this research was to register the number of cases of visual disabilities in the Republic of Ireland and improve the quality of the professionals.
A research study completed in Gambia and Mongoliaby Faal, Minassian, Sowa & Foster, (1989)provided findingsregarding the prevalence and causes of blindness and visual impairment.The studydescribedthe results of a survey completed in 1989 and 1994. In Gambia, 8,174 persons from 0 to 91years of age were examined. The prevalence of blindness was 0.7% and low vision was 1.4%. The most common causes of blindness for this region were cataracts (55%), non-trachomatous corneal opacity, and trachoma (Faalet al., 1989).
In a Mongolian study conducted by Baasanhu, Johnson, Burendei, &Minassian (1994), a population sample of 4,345 peoplewas taken. Of those completing the survey,95% of the population, male and female, aged 40 years and older responded to the survey questions. Findings revealed that 1.52% was blind, 8.10% had low vision, and 2.53% had monocular blindness. The climate in Mongolia was one of the reasons attributed for the high prevalence of chronic actinic keratopathy. Findings surmised this to be the case due to residents being exposed to the reflection of the sun’s light off of the snow; which can last up to six out of the twelve months per year. The increased exposure to UV light some 260 days per year when sunlight is most pervasive, combined with high winds, contributes to corneal blindness and low vision (Baasanhu et al. 1994). This research paper based on data found in Mongolia shows that the major causes of blindness between 1991 and 1992 were cataract (36.2%) and glaucoma (34.8%) (Baasanhu et al. 1994).
Goggin and O’Keefe (1991)affirmed that several countries from Africa and third world countries present a more precise statistic on the prevalence of blinding disease than developed countries:
“Last year the results of the national survey of blindness and low vision in TheGambia were published. A large random stratified sample of this country’spopulation was examined (8,174 people). The main causes of
blindness found were cataract and uncorrected aphakia, non
trachomatouscorneal opacity and phthisis bulbi, and trachoma” (p.427).
Based on the results of the research in Gambia, it was found a necessityof more studies in the visual field in that region.
In Pakistan(Jadoon, Dinnen, Bourne, Shah, Khan, Johnson, Gilbert, & Khan, 2006), researchers aimed to determine the prevalence of blindness and visual impairment in people aged 30 years and older. The relationship between the visual disability and the socio-demographic risk factors were studied as well.A group of researchers used a stratified, cluster random sampling of 16,507 adults. The participants had a vision consultation, including a measurement of visual acuity, and eye exams such as auto refraction, biometry, and fundus optic disc examination.
The results associated the age of the person and the severity of the visual impairment. The results were presented comparing visual acuity to gender, location, age, and socio economic indicators. Regarding gender, there was no significant difference. However, when considering gender and age together, the prevalence of low vision was higher in women of all age ranges except 30 to 39 years old. The results showed a 30% probability of womenbecoming visually impaired over men. Regarding location, Punjah and Baluchistan had the highest prevalence of visually impaired persons. A high percentage of women (85.2%) and men (53.8%) involved in the research were illiterate. The survey found inequalities in service delivery with women, individuals living in rural areas and those that are illiterate that have low surgical coverage.There was a direct correlation between visual acuity being tied to educational status. In the 30-39 year old range, 60% were found to be illiterate as compared to 91% of residents aged 70 years and up. Illiteracy was more prevalent in rural areas than urban communities. The occurrence of blindness was more predominant in the illiterate participants(Jadoon,et al., 2006).
A survey regarding prevalence and causes of visual impairment in school-age children was conductedin eight locations in six countries: 2 locations in India, 2 locations in China, and one location in each of Malaysia, Chile, Nepal, and South Africa. Between4,082 to 6,527 children from 5 to 15 years of age were tested in their respectivecountry. The researchers measured visual acuity, performed acycloplegicauto refraction test,and assessed best-corrected acuities. Sample in all countries were randomly chosen.The results indicated there were60 children with the best corrected visual acuity (< 6/18 or 20/60). The prevalence of functional low vision was higher in girls than in boys. Also, another finding showed that functional low vision increases with age and it is not directly related to cultural background (Gilbert, Ellwein, & the Refractive Error Study in Children Study Group Gilbert, 2008).
Alagaratnam, Sharma, Lim, & Fleck (2002) conducted a study on children with visual impairment at one school in Edinburgh, Scotland. The purpose of the study was to assess the aetiology and changing patterns of childhood blindness in one school for the blind in United Kingdom and to assess the use of World Health Organization. The WHO Prevention of Blindness Program with the International Centre for eye Health develops a standard methodology to report the causes of visual impairment in children.
There were 107 children participating in the study (54 males and 53 females). Most of the children (77%) were between 5 and 10 years old. Only 23% had no other impairment. The purpose of this study was to determine the causes of visual disorders and impairment in children. It primarily focuses on students in a UK school for the blind and findings were compared to that of children of same ages in other countries. Retinal dystrophies like Leber’sAmaurosis, albinism, and achromatopsia accounted for 43% of the cases. The second leading cause was perinatal factors related to 40% of the participants (2002). The anatomical causes of abnormality that lead to blindness appear in the central nervous system or the optic nerve as the commonest cause of visual impairment. Optic atrophy was responsible for visual impairment in nine children while nineteen had bilateral retinal detachment. Retinal disease was another cause of visual impairment where nineteen children had retinal detachment due to prematurity.

Accessible Presentation of information for people with visual disabilities

The term people with visual disabilities refer to full range of people that have visual disabilities. This includes people who are blind, who have little or no functional vision, and people who have low vision. According to Power & Jurgensen (2010), the present world digital technology provides new devices with diverse uses around the world. The devices such as phones and web technologies have changed the way people communicate. The hindrance with the technological devices is that their accessibility and usability does not apply the same for mainstream users and users with disabilities. The universal access for all people sadly lags behind technical advancement that leave many with technologies difficult or in some cases impossible to use for people with disabilities (Power & Jurgensen, 2010). Some of alternatives for people with visual disabilities include audio presentation and tactile presentation. In audio media, one can convey information through sound to a user beginning from non-speech sounds and later synthesized speech.
Power and Jurgensen (2010) define auditory icon as the use of real-world sound to communicate the interaction of a user with objects in a scene. The sounds relate to a task performed and the object of interaction by the user. For instance, Recycle Bin icon is a graphical user interface found at the desktop of a personal computer to indicate visually of the documents that have to be cleared from the system. When a user opts to empty the Recycle Bin, they will hear an auditory icon of papers shuffled out of the rubbish bin. The sound heard is a digital representation of the real-world counterparts. One can adjust the sound parameters to indicate the identity of object manipulated. It is possible to adjust different parameters of sound such as the tempo or pitch played. It is hypothesized that nomic mappings of sounds to tasks are better than metaphorical mappings. In contrast, the ear cons are musical melodies that are symbolic of tasks and objects. One cannot ignore the design of interface for people with visual disabilities while using speech for communicating information.
Some of the usability parameters that designers of visual disability devices must consider include: (i) technology- the hardware synthesizers produce quality sound and accurate speech synthesis. The only challenge is their expensive nature and they require additional workspace (Gambler et al. 2004). The software synthesizers are also expensive and a person may opt for the open source initiatives. The software synthesizers take advantage of the existing sound card hardware available to most personal computers. (ii) Speed-The average speed for the screen readers is nearly three times slower than the average speed of user with visual disability. For one to compensate the varying comprehension rates, any application that uses text to speech technology should provide an accessible means to adjust the speed of the speech output. (iii) Voice- most of the speech synthesis systems provide different voices that range from low male to high childlike. Just like speed, voice used to vocalize text is the customizable option for the user. The use of three-dimensional sound (3D) interfaces is likely to become more common since it produces a signal that matches the transformation of a sound from the point of origin to the arrival in the ear canal. The signal produced varies with the relative position of the head. If the sound originates on the left side of the head, the sound wave signal will reach the left ear first whilst the right ear will receive an altered signal caused by the wave shadowed by the head. The sound systems contain ambiguous set of Head-Related Transfer Functions (HRTF). The components bear numbers to represent time delay, amplitude, and tonal transformations of sounds from various points around the head. The purpose of HRTF is to alter the sound signal sent toward the ear to give an illusion that it comes from the 3D space (Gambler et al. 2004). One can record HRTF formation through a series of tone experiments with microphones placed in the ear canal of a specific person. In terms of hardware, one can create 3D sound applications using the headphone or loudspeakers. In case one chooses the loudspeaker, one can place them in traditional stereo configuration, a sound wall that has bank of speakers, or multiple surrounding speakers. In case one uses headphones, the HRTF will be simple, as information will be projected directly into the appropriate ear. The problem with loudspeakers is that they have crosstalk where sound waves intended for one year will travel to the other. The extra signals will disrupt localization effects of the user. To counteract the signals one can add crosstalk filters to the signals to cancel the unwanted sound waves and prevent them from reaching the wrong ear.
Tactile media is another form of information presentation for people with visual disabilities (Fahim & Nedwick, 2014). The production of tactile documents lags behind print for the mainstream users. Some of the offline documents produced by technologies do not use a desktop computer include maps, calendars, and textbooks. One can generate tactile documents in ad hoc way while working with an individual with visual disability .some of the documents consist of tactile graphics displayed in a 2D space with various materials providing depth or texture to the graphic. Several examples of variable height are static pictures prepared to provide depth of an image by reproducing contours or raised areas by attaching materials to a background and using fasteners to identify landmarks of interest. One can use ink that dries to a raised surface. There are several prefabricated kits designed to assist in building pictures such as the Tactual Diagram that provides felt shapes and lines for the background. Tactile-experience pictures are mainly graphics used by children created with sandpaper, wood, and other materials with unique tactile sensations. A buildup display consists of household materials such as string and drawing pins used to draw attention to landmarks of interest in the tactile scene (Fahim & Nedwick, 2014). A fast immediate generation of tactile documents that has a raised line drawing board will produce raised lines. The technique has limitations in that it cannot support mass production of graphics. For that reason, one can use traditional embossing techniques, thermoform materials, computer presentation, or other techniques
Embossing refers to printing of raised dots concentrated to each other that help to create 2D structures. One can produce the dots using embossing printers or through heat transfer copying. The dots are the same distant apart as the standard Braille character almost 2.5mm that allow easy generation of Braille text intermixed with other graphical elements. The TIGER embosser is an example of embossing printer that provides more finely spaced dots for the production of near continuous raised lines and surfaces (Fahim & Nedwick, 2014).
Microcapsule paper reproductions consist of polythene paper with a polystyrene microcapsule layer coating on one side. The capsules expand when heated to raise the areas of the paper and give the medium its colloquial name of swell paper. One produces the documents through an application of graphic elements to the paper using a dark colored ink pen or through standard printing techniques (Power & Jurgensen, 2010). The limitation of this technique is that there is a possibility of encountering skin burns through direct skin contact with the heated tip.
Thermoforming is a technique of generating tactile document from pre-tooled dyes. The technique consists of molding a metal dye into a shape of the document that includes Braille with the printed text, line graphics, and multi-tiered graphics. One should heat the sheet to cause it to have a mould. When the material cools, one should remove the sheet firms around the mold to create a replica of the document. The tactile techniques in use by people with visual disabilities suffer some limitations such as: (i) size- the documents are substantially larger than standard print documents. Packing of multilevel vacuum form documents and staking of materials is impossible that result in storage problems. (ii) Loss of information- lack of space and resolution leads to loss of fine detail (Power & Jurgensen, 2010). The loss of information could lead to misinterpretation of data where the reader encounters confusion in the course of navigating tasks. (iii) cost- it is expensive to purchase the embossing printers together with the cost of producing the media. (iii) Immutability- the only way to incorporate changes in the tactile document is to regenerate the whole document that is very expensive and nearly impossible to ensure documents are up to date. Most of the problems with tactile offline media come from the fact that they cannot adjust to the needs of individual user. Some of the tablet displays can convey audio information associated with tactile documents. One places tactile overlay` on top of the display area as the user explores the surface with their fingers. User finger will exhibit pressure from the display in the location of the computer to decode speech and other audio information. Tablet displays can address information loss problem found in offline documents through audio annotations since it does not address cost, reproduction, and size issues. One can refresh dynamic display quickly where a user can page through a document that is rare and expensive to produce.

Text transcription-electronic text documents are the best for people with visual disabilities.

Audio presentation of text- either it is in the form of speech recordings in audio books and digital talking books or synthesized speech produced by text to speech technology that one can combine with screen readers to access computer text (Power & Jurgensen, 2010). The audio book formats are present in the mainstream media such as novels, textbooks, and other printed materials. The current initiative is to change them into recordings and distributed to blind populations. The earlier versions had an analogue format where a user had to navigate forward or backward. The analogue format had challenges in reviewing a specific section. With the introduction of digital media, users had to abandon analogue tapes in favor of CDSs and portable digital music players. The nature of the digital media provided the ability to provide chapter and section markers that would assist in navigating the text. The Digital Accessible Information Systems (DAISY) oversees the process of standardizing Digital Talking Books (DTB). The latest standard is DAISY 2.0 developed through an interactive process to include markup standards. The standard uses World Wide Web Consortium languages such as SMIL to permit the synchronization of audio presentation of the document. Instead of using recordings, a user can apply the text to systems in an automatic way where one reads aloud the text. Earlier on victims of visual disabilities used monotone speech generation to convey information to equipment operators or the early telephony applications. For example, the Kurzweil reading machine performs basic rendering of text to speech from the scanned printed documents. The limitation for the device includes insufficient understanding to the user due to the use of simple transcription of character representation. With no sufficient prosodic cues to perceive and evaluate the context presented, it is difficult for the listener to comprehend long streams of speech (Gambler et al. 2004).
Presently, there is a lot of work to process the prosodic that will see translation of English, German, Latin, French, Japanese, Chinese, and Italian. Most developing countries are multilingual and they have to prepare a dual language system for people with visual disabilities. Some of the OECD nations face funds constrains of providing text to speech output in dual language format. An electronic form will support quick transformation of text to speech technology such as direct entry when one has a word processor (Gambler et al. 2004). Alternatively, one scans the paper documents to electronic form and use Optical Character Recognition (OCR) device to retrieve character information.
Enhanced visual presentation of text- the low vision users can benefit from an increase of font sizes that require large screens or screen magnification technology. In addition to that, the people with low vision can benefit from alternative color contrast for text against backgrounds. The color contrast calculation for cathode ray tube television set is the most accurate to describe perception of color contrast for the user population. The work does not necessarily account for the preference of an individual as the ability to adjust the color of text and background is the requirement for accessibility (Fahim & Nedwick, 2014).
Tactile presentation of text-one can employ the touch method to present documents other than auditory presentation. There are different codes in Braille that can assist in reading text. The original creator of Braille code was Louis Braille in 1829 the code serves the purpose of transcription text documents into tactile form. The codes consist of characters of six to eight dots in columns of three to four dots. The optimal spacing for the dots is subtle and precipitates discussion in the design of a new device. There are currently different Braille-style codes used to translate variety of materials such as music, chemistry notation, computer symbols, flow charts, and mathematics. Researchers focus on the best way to transcribe printed documents into Braille. Transcribers have been available since the first use of Braille in manual transcription. The introduction of electronic computers enables automatic transcription of text to Braille and alleviate some of the challenges found in using manual transcribers. The embossing machines enable automatic transcription of text into Braille (Fahim & Nedwick, 2014).
Mathematics presentation-the solution to present text does not work with numbers in the context of mathematics. From the structure of mathematic notation, a more appropriate plethora of audio presentation will work. Some of the questions in the design phase include the ability of the reader to vocalize the formula and what to read first between denominator and numerator while dealing with fractions. Researchers have been able to come up with different prototype that results in ambiguity that results from the perception of the mathematical notation without understanding the intention of the author. An alternate audio presentation is to generate a tactile representation of mathematical notation explored using hands.
Audio presentation of mathematics- most of the prototypes that present mathematics drew on the availability of audio hardware to generate speech interpretations of the notation (Fahim & Nedwick, 2014). The experimental evidence shows that internalizing the structure of mathematical notation will be difficult once presented in the audio format. This is due the increase of cognitive load on the reader that has to understand the notation while focusing on navigating through the mathematical document to detect the terms of interest. Raman is a researcher that attempts to solve navigation problems based on own experience. Edward and Stevens provides a math talk system whose intention is to target high school level students and early graduate work in mathematics and complex algebra. The researchers recognize that benefit of visual sense is that readers do not to remember all the information presented at one time (Power & Jurgensen, 2010). The difference between sighted and blind mathematicians is that sighted mathematicians use paper to record progress while blind mathematicians have to recall the previously used symbols. The Math talk symbols permit audio browsing of algebraic equations through an active reading process with the user participating in the display and review of mathematical notation.
Tactile presentation of mathematics provides two alternatives to present mathematics namely Braille codes and Dots-Plus system. The Nemeth code is the standard code for tactile presentation mathematics in the West. It uses context symbols that change from literal and mathematics context. The code is the transcription language and it is best for the individuals doing transcription to have technical knowledge on mathematics material. The Dots plus Braille combines graphical characters with specialized numerical Braille symbols. The method addresses some problems such as translating mathematics into tactile form through Dots-Plus Braille font characters substituted for their print equivalents. Dots Plus does not use number mode rather it has an additional dot for the characters representing digits in literary Braille number mode. The exotic symbols such as summation and integration symbols represent as direct tactile translations of their visual equivalents.
The internet and the World Wide Web have changed the way people interact with information. The internet has virtually all information on every subject where users can peruse and read at their own leisure and pleasure. The web originally holds a great deal of potential to help eliminate the gap in access to information between the mainstream users and those with visual disabilities. The web pages that consist of text and few graphics promise to become a resource accessible through screen reading technology and Braille displays. As the connection speeds increased, users began to demand more variety in their media. The design of new technologies provides graphics, games, and more on the web (Power & Jurgensen, 2010). They were produced fast so that they rarely considered accessibility factors. Companies focus to provide more content faster in what appear to be a continuing trend in accessibility. Majority of the websites consist of non-text visual content with no descriptive audio or tactile counterpart, much of the content is unavailable to the visually disabled. There are few thematic areas in literature that elaborate how to make the web pages accessible to the impaired that include guidelines that govern the creation of web sites, specialized browser design, de construction of the web page content, and presentation strategies. The commonly applied internet standards and guidelines come from World Wide Web Consortium through the Web Accessibility Initiative. The organization provides a forum for researchers to contribute towards the content presented on the web. One of the recent developments by the organization is the completion of benchmarking tools and methods for the web to assist the people with visual disabilities. Some of the results produced include evaluation of color contrast equations that describe user’s perceptions, evaluation of factors that affect navigational consistencies between web pages, and comparison of the accessibility and usability of validation tools (Power & Jurgensen, 2010).
Haptics is the newest technology for information access by people with visual disabilities. It refers to the detection of external stimuli such as kinesthetic forces and body temperature. It provides a traditional 2D interface with robotics and game system controllers. It provides varying level of variation to a user that is blind.

Limitations

Some studies are resigned to particular populations and age groups; thus, presenting limitations. The limited findings resulted in research being outdated in such studies as the research done in Gambia in 1989. There is some research focused on children but not enough by comparison to what is found in adult studies. The Mongolian study is difficult to compare to other studies because climate plays a huge role in outcomes of visual impairments found among its populations. The research conductedin Brazil,is targeted to one of the smaller regions, Botucatu, in which the population is smaller by comparison to other parts of the country, as well as other countries researched.

Conclusion

All papers described statistically the visual impairments presented in their studies. Most of them also described actions in order to diminish visual impairments. Several eye conditionssuch as myopia, hyperopia, cataracts, low vision, and blindness that could be prevented or eliminated have been discussed in the papers.Several studies show that even having access to an eye doctor sometimes is a hard task to be done. Some countries such as Gambia and Mongolia have limited to the number of specialists to fulfill the population’s needs as mentioned in research conducted. Gambia, for example, has one ophthalmologist to 800,000 residents, making effective treatment in prevention and cures of various visual impairments nearly impossible.
Research done in Brazil shows deficiency on diagnosing the correct refractive errors, cataract, and retinal diseases.The investigation in Pakistan revealed a significant number of older(male and female) population to be illiterate and presenting a higher frequency of visual disabilities and blindness. Findings reveal that most of the cases researched are preventable; with early detection being primary to receiving effective treatment that produces successful outcomes.
Studies done in economically developed countries such as Australia, United States, and Europe, also show restrictions and lack of professionals in the research field. Vision loss is a major issue for communities and countries around the world both in the developed economies and developing countries; Vision 2020 provides a global focus for activity and facilitates the development of sustainable programs.
According to the World Health Organization (2013), fact sheet, the major causes of visual impairments are uncorrected refractive errors (myopia, hyperopia or astigmatism) – 43%, unoperated cataract – 33%, and glaucoma – 2%. Various research reviewed here supports these statistics. Information presented in this literature review shows the most predominant vision problems around the world likely due to lack of treatments and correction of visual impairments. It can be concluded that all of the research findings as a whole consistently show a lack of medical professionals, resources, and means of educating populations about visual impairment. In turn, the research justifies the high number of visual problems worldwide that are still yet to be solved.
This would shed great light on the research that is already in existence about this issue, while aiding researchers in finding gaps in existing data providing a more intentional focus. Collaboration among these organizations and many others in conjunction with the global medical, research community is continually needed to build upon existing research in order to generate new advances in the treatment and prevention of visual impairments and blindness.

References

Alagaratnam, J., Sharma, T. K., Lim, C. S., & Fleck, B. W. (2002).A survey of visual impairment in children attending Royal Blind School, Edinburgh using the WHO childhood visual impairment database.Eye, 16, 557-561. DOI: 10.1038/sj.eye.6700149
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WePapers. (2021, January, 28) Definition Of Low Vision And Blindness Literature Reviews Example. Retrieved August 05, 2021, from https://www.wepapers.com/samples/definition-of-low-vision-and-blindness-literature-reviews-example/
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Definition Of Low Vision And Blindness Literature Reviews Example. Free Essay Examples - WePapers.com. https://www.wepapers.com/samples/definition-of-low-vision-and-blindness-literature-reviews-example/. Published Jan 28, 2021. Accessed August 05, 2021.
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