Visual impairment

From Wikipedia, the free encyclopedia - View original article

Visual impairment
Classification and external resources
Hyperopia.gif
ICD-10H54
ICD-9369
 
Jump to: navigation, search
Visual impairment
Classification and external resources
Hyperopia.gif
ICD-10H54
ICD-9369

Visual impairment (or vision impairment) is vision loss (of a person) to such a degree as to qualify as an additional support need through a significant limitation of visual capability resulting from either disease, trauma, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive correction or medication.[1][2][3] This functional loss of vision is typically defined to manifest with

  1. best corrected visual acuity of less than 20/60, or significant central field defect,
  2. significant peripheral field defect including homonymous or heteronymous bilateral visual, field defect or generalized contraction or constriction of field, or
  3. reduced peak contrast sensitivity with either of the above conditions.[1][2][3][4]

Eye disorders which can lead to visual impairments can include retinal degeneration, albinism, cataracts, glaucoma, muscular problems that result in visual disturbances, corneal disorders, diabetic retinopathy, congenital disorders, and infection." Visual impairment can also be caused by brain and nerve disorders, in which case it is usually termed cortical visual impairment (CVI).

The American Medical Association's Guides to the Evaluation of Permanent Impairment attempts to provide "a standardized, objective approach to evaluating medical impairments." The Visual System chapter "provides criteria for evaluating permanent impairment of the visual system as it affects an individual's ability to perform activities of daily living."[5] The Guide has estimated that the loss of one eye equals 25% impairment of the visual system and 24% impairment of the whole person;[5][6] total loss of vision in both eyes is considered to be 100% visual impairment and 85% impairment of the whole person.[5]

Visual impairments have considerable economic impact on even developed countries.[7] 'A major proportion of global visual impairment is preventable'.[8] An update based on census data of 2010 in the United States projects that 13 million Americans aged 40 and older will have a visual impairment or be blind by the year 2050.[9]

Classification[edit]

Anyone with reduced vision not corrected by spectacles or contact lenses is visually impaired. The World Health Organization uses the following classifications of visual impairment. When the vision in the better eye with best possible glasses correction is:

Legal blindness

There are also levels of visual impairment based on visual field loss (loss of peripheral vision).

Go to visual acuity to consult an international visual acuity expression chart.

In the United States, any person with vision that cannot be corrected to better than 20/200 in the best eye, or who has 20 degrees (diameter) or less of visual field remaining, is considered legally blind or eligible for disability classification and possible inclusion in certain government sponsored programs.

United States[edit]

In the United States, the terms "partially sighted", "low vision", "legally blind" and "totally blind" are used by schools, colleges, and other educational institutions to describe students with visual impairments.[10] They are defined as follows:

  1. Partially sighted indicates some type of visual problem, with a need of person to receive special education in some cases;
  2. Low vision generally refers to a severe visual impairment, not necessarily limited to distance vision. Low vision applies to all individuals with sight who are unable to read the newspaper at a normal viewing distance, even with the aid of eyeglasses or contact lenses. They use a combination of vision and other senses to learn, although they may require adaptations in lighting or the size of print, and, sometimes, Braille;
    1. Myopic - unable to see distant objects clearly, commonly called near-sighted or short-sighted
    2. Hyperopic - unable to see close objects clearly, commonly called far-sighted or long-sighted
  3. Legally blind indicates that a person has less than 20/200 vision in the better eye after best correction (contact lenses or glasses), or a field of vision of less than 20 degrees in the better eye; and
  4. Totally blind students learn via Braille or other non-visual media.

Health effects[edit]

Visual impairments may take many forms and be of varying degrees. Visual acuity alone is not always a good predictor of the degree of problems a person may have. Someone with relatively good acuity (e.g., 20/40) can have difficulty with daily functioning, while someone with worse acuity (e.g., 20/200) may function reasonably well if their visual demands are not great.

Some people who fall into this category can use their considerable residual vision – their remaining sight – to complete daily tasks without relying on alternative methods. The role of a low vision specialist (optometrist or ophthalmologist) is to maximize the functional level of a patient's vision by optical or non-optical means. Primarily, this is by use of magnification in the form of telescopic systems for distance vision and optical or electronic magnification for near tasks.

People with significantly reduced acuity may benefit from training conducted by individuals trained in the provision of technical aids. Low vision rehabilitation professionals, some of whom are connected to an agency for the blind, can provide advice on lighting and contrast to maximize remaining vision. These professionals also have access to non-visual aids, and can instruct patients in their uses.

The subjects making the most use of rehabilitation instruments, who lived alone, and preserved their own mobility and occupation were the least depressed, with the lowest risk of suicide and the highest level of social integration.

Those with worsening sight and the prognosis of eventual blindness are at comparatively high risk of suicide and thus may be in need of supportive services. These observations advocate the establishment and extension of therapeutic and preventative programs to include patients with impending and current severe visual impairment who do not qualify for services for the blind. Ophthalmologists should be made aware of these potential consequences and incorporate a place for mental health professionals in their treatment of these types of patients, with a view to preventing the onset of depressive symptomatology, avoiding self-destructive behavior, and improving the quality of life of these patients. Such intervention should occur in the early stages of diagnosis, particularly as many studies have demonstrated how rapid acceptance of the serious visual handicap has led to a better, more productive compliance with rehabilitation programs. Moreover, psychological distress has been reported (and is exemplified by our psychological autopsy study) to be at its highest when sight loss is not complete, but the prognosis is unfavorable.10 Therefore, early intervention is imperative for enabling successful psychological adjustment.[11]

Cause[edit]

Epidemiology[edit]

Distribution of visual impairment[edit]

By age: Visual impairment is unequally distributed across age groups. More than 82% of all people who are blind are 50 years of age and older, although they represent only 19% of the world's population. Due to the expected number of years lived in blindness (blind years), childhood blindness remains a significant problem, with an estimated 1.4 million blind children below age 15.

By gender: Available studies consistently indicate that in every region of the world, and at all ages, females have a significantly higher risk of being visually impaired than males.

By geography: Visual impairment is not distributed uniformly throughout the world. More than 90% of the world's visually impaired live in developing countries.[41]

Since the estimates of the 1990s, new data based on the 2002 global population show a reduction in the number of people who are blind or visually impaired, and those who are blind from the effects of infectious diseases, but an increase in the number of people who are blind from conditions related to longer life spans.[41]

Range of Visual Impairment[edit]

Severely Sight Impaired

Sight Impaired

Low Vision

Communication[edit]

Communication Barriers[edit]

Communication with the visually impaired can be more difficult than communicating with someone who doesn't have vision loss. However, many people are uncomfortable with communicating with the blind, and this can cause communication barriers. One of the biggest obstacles in communicating with visually impaired individuals comes from face-to-face interactions.[43] There are many factors that can cause the sighted to become uncomfortable while communicating face to face. These factors are more non-verbal rather than verbal types of communication. These factors, which Rivka Bialistock[43] mentions in her article, include:

The blind person sends these signals or types of non-verbal communication without being aware that they are doing so. These factors can all affect the way an individual would feel about communicating with the visually impaired. This leaves the visually impaired feeling rejected and lonely.

Adjusting the visually impaired peoples attitude to reduce communication barriers[edit]

In the article Towards better communication, from the interest point of view. Or—skills of sight-glish for the blind and visually impaired, the author, Rivka Bialistock [43] comes up with a method to reduce individuals being uncomfortable with communicating with the visually impaired. This method is called blind-glish or sight-glish, which is a language for the blind, similar to English. For example, babies, who are not born and able to talk right away, communicate through slight-glish, simply seeing everything and communicating non-verbally. This comes naturally to sighted babies, and by teaching this same method to babies with a visual impairment can improve their ability to communicate better, from the very beginning.

Adjusting the sighted peoples attitude towards the visually impaired to reduce communication errors[edit]

To avoid the rejected feeling of the visually impaired, people need to treat the blind the same way they would treat anyone else, rather than treating them like they have a disability, and need special attention. People may feel that it is improper to, for example, tell their blind child to look at them when they are speaking. However, this contributes to the sight-glish method.[43] It is important to disregard any mental fears or uncomfortable feelings people have while communicating (verbally and non-verbally) face-to-face.

Ability to communicate with surroundings[edit]

Individuals with a visual disability not only have to find ways to communicate effectively with the people around them, but their environment as well. The blind or visually impaired rely largely on their other senses such as hearing, touch, and smell in order to understand their surroundings.[44]

Sound[edit]

Sound is one of the most important senses that the blind or visually impaired use in order to locate objects in their surroundings. A form of echolocation is used in which the person uses sound waves, generated from speech or other forms of noise such as cane tapping, which reflect off of objects and bounce back at the person giving them a rough idea of where the object is. This does not mean they can depict details based off of sound but rather where objects are in order to interact, or avoid them. Increases in atmospheric pressure and humidity increase a person's ability to use sound to their advantage as wind or any form of background noise impairs it.[44]

Touch[edit]

Touch is also an important aspect of how blind or visually impaired people perceive the world. Touch gives immense amount of information in the persons immediate surrounding.Feeling anything with detail gives off information on shape, size, texture, temperature, and many other qualities. Touch also helps with communication; braille is a form of communication in which people use their fingers to feel elevated bumps on a surface and can understand what is meant to be interpreted. There are some issues and limitations with touch as not all objects are accessible to feel, which makes it difficult to perceive the actual object. Another limiting factor is that the learning process of identifying objects with touch is much slower than identifying objects with sight. This is due to the fact the object needs to be approached and carefully felt until a rough idea can be constructed in the brain.[44]

Smell[edit]

Certain smells can be associated with specific areas and help a person with vision problems to remember a familiar area. This way there is a better chance of recognizing an areas layout in order to navigate themselves through. The same can be said for people as well. Some people have their own special odor that a person with a more trained sense of smell can pick up. A person with an impairment of their vision they can use this to recognize people within their vicinity without them saying a word.[44]

Impact of Visual Impairment on Communication Development[edit]

Visual impairment can have profound effects on the development of infant and child communication. The language and social development of a child or infant can be very delayed by the inability to see the world around them.

Social Development[edit]

Social development includes interactions with the people surrounding the infant in the beginning of its life. To a child with vision, a smile from a parent is the first symbol of recognition and communication, and is almost an instant factor of communication. For a visually impaired infant, recognition of a parent's voice will be noticed at approximately two months old, but a smile will only be evoked through touch between parent and baby. This primary form of communication is greatly delayed for the child and will prevent other forms of communication from developing. Social interactions are more complicated because subtle visual cues are missing and facial expressions from others are lost.

Due to delays in a child's communication development, they may appear to be disinterested in social activity with peers, non-communicative and un-education on how to communicate with other people. This may cause the child to be avoided by peers and consequently over protected by family members.

Language Development[edit]

With site, much of what is learned by a child is learned through imitation of others, where as a visually impaired child needs very planned instruction directed at the development of postponed imitation. A visually impaired infant may jabber and imitate words sooner than a sighted child, but may show delay when combining words to say themselves, the child may tend to initiates few questions and their use of adjectives is infrequent. Normally the child's sensory experiences are not readily coded into language and this may cause them to store phrases and sentences in their memory and repeat them out of context. The language of the blind child does not seem to mirror his developing knowledge of the world, but rather his knowledge of the language of others.

A visually impaired child may also be hesitant to explore the world around them due to fear of the unknown and also may be discouraged from exploration by overprotective family members. Without concrete experiences, the child is not able to develop meaningful concepts or the language to describe or think about them.[45]

Diagnosis[edit]

Scientists track eye movements in glaucoma patients to check vision impairment while driving

It is critical that all people be examined by someone specializing in low vision care prior to other rehabilitation training to rule out potential medical or surgical correction for the problem and to establish a careful baseline refraction and prescription of both normal and low vision glasses and optical aids. Only a doctor is qualified to evaluate visual functioning of a compromised visual system effectively.[46]

Treatment[edit]

Aside from medical help, various sources provide information, rehabilitation, education, and work and social integration.

Optical aids[edit]

The vast majority of patients with low vision can be helped to function at a higher level with the use of low vision devices. Low vision specialists recommend appropriate low vision devices and counsel patients on how better to deal with their reduced vision in general. Many government and private organizations exist to aid the visually impaired.

In an article, Augusto Bruix Bayés[47] mentions that the main principle behind low vision is to magnify the image using various tools.

Improving far sight: works best with static objects

Improving near sight: the person must work closer to the object

Improving sensitivity to contrast: the person must use special optical filters

Other tools:

Efficacy of optical aids[edit]

In a study performed by this specialist on 1,000 patients, all subjects with a visual acuity above 0.02 decimal (20/1000 feet) significantly improved their vision. From this group, 48% were very satisfied with their visual aids, 44% were satisfied, 5% little satisfied and 3% unsatisfied. Adaptation process to visual aids In the patient's first visit, the most adequate options for their particular case are studied, taking into consideration their psychological, cultural, social and work factors, and the degree of improvement experienced with the selected aids, advising the patient on which aids improve quality of life. After the specific adaptation, there is a follow up to ensure the patient is correctly using and taking the best advantage of the visual aids. In some cases (approx. 4%), the initial visual aids must be changed. Once the patient is released, a report on their first visit and follow up is given to their eye doctor or the professional who made the referral. We believe that low vision, as a complementary technique to ophthalmology, has a great future, due to the progress of science, the increase of life expectancy, and the increasing need people have to access information.

Other aids[edit]

For the totally blind, there are books in braille, audio-books, and text-to-speech computer programs, machines and e-book readers. Low vision people can make use of these tools as well as large-print reading materials and e-book readers that provide large font sizes.

Computers are important tools of integration for the visually impaired person. They allow, using standard or specific programs, screen magnification and conversion of text into sound or touch (Braille line), and are useful for all levels of visual handicap. OCR scanners can, in conjunction with text-to-speech software, read the contents of books and documents aloud via computer. Vendors also build closed-circuit televisions that electronically magnify paper, and even change its contrast and color, for visually impaired users. For more information, consult Assistive technology.

In adults with low vision there is no conclusive evidence supporting one form of reading aid over another.[48] In several studies stand-based closed-circuit television and hand-held closed-circuit television allowed faster reading than optical aids.[48] While electronic aids may allow faster reading for individuals with low vision, portability, ease of use, and affordability must be considered for people.[48]

Children with low vision sometimes have reading delays, but do benefit from phonics-based beginning reading instruction methods. Engaging phonics instruction is multisensory, highly motivating, and hands-on. Typically students are first taught the most frequent sounds of the alphabet letters, especially the so-called short vowel sounds, then taught to blend sounds together with three-letter consonant-vowel-consonant words such as cat, red, sit, hot, sun. Hands-on (or kinesthetically appealing) VERY enlarged print materials such as those found in "The Big Collection of Phonics Flipbooks" by Lynn Gordon (Scholastic, 2010) are helpful for teaching word families and blending skills to beginning readers with low vision. Beginning reading instructional materials should focus primarily on the lower-case letters, not the capital letters (even though they are larger) because reading text requires familiarity (mostly) with lower-case letters. Phonics-based beginning reading should also be supplemented with phonemic awareness lessons, writing opportunities, and lots of read-alouds (literature read to children daily) to stimulate motivation, vocabulary development, concept development, and comprehension skill development. Many children with low vision can be successfully included in regular education environments. Parents may need to be vigilant to ensure that the school provides the teacher and students with appropriate low vision resources, for example technology in the classroom, classroom aide time, modified educational materials, and consultation assistance with low vision experts.

Improving Health Care Access[edit]

Visual impairment has the ability to create consequences for health and well being. Visual impairment is increasing especially among older people. It is recognized that those individuals with visual impairment are likely to have limited access to information and healthcare facilities, and may not receive the best care possible because not all health care professionals are aware of specific needs related to vision.

See also[edit]

References[edit]

  1. ^ a b Arditi, A., & Rosenthal, B. (1998). "Developing an objective definition of visual impairment." In Vision '96: Proceedings of the International Low Vision Conference (pp. 331-334). Madrid, Spain: ONCE.
  2. ^ a b Medicare Vision Rehabilitation Services Act of 2003 HR 1902 IH
  3. ^ a b larrybelote.com
  4. ^ medem.com
  5. ^ a b c AMA Guides
  6. ^ Eye Trauma Epidemiology and Prevention
  7. ^ Taylor, HR; Pezzullo, ML; Keeffe, JE (2006). "The economic impact and cost of visual impairment in Australia". British journal of ophthalmology 90 (3): 272–5. doi:10.1136/bjo.2005.080986. PMC 1856946. PMID 16488942. 
  8. ^ Agarwal, R (1997), Prevention of visual impairment, British Journal of Optometry and Dispensing, 5(2), page 48.
  9. ^ Anon (2012), Organization and Institution News, Visual impairment and blindness increase in over 40 population this past decade, Optometry and Vision Science, 89(8), 1239.
  10. ^ National Dissemination Center for Children with Disabilities
  11. ^ de Leo et al.: Blindness, Fear of Sight Loss, and Suicide, Psychosomatics 1999; 40:339–344
  12. ^ a b Onojafe, I. F., Adams, D. R., Simeonov, D. R., Zhang, J., Chan, C., Bernardini, I. M., ... Brooks, B. P. (2011). Nitisinone improves eye and skin pigmentation defects in a mouse model of oculocutaneous albinism. Journal of Clinical Investigation, 121(10), 3914-3923. doi:10.1172/JCI59372
  13. ^ a b c Rashad, M. A. (2012, Annual). Pharmacological enhancement of treatment for amblyopia. Clinical Ophthalmology, 6, 409. Retrieved December 5, 2013, from Academic OneFile.
  14. ^ a b Gilbert, C., & Foster, A. (2001). Childhood blindness in the context of vision 2020--the right to sight. Bulletin Of the World Health Organization, 79(3), 227-232. Retrieved from ehis.ebscohost.com.central.ezproxy.cuny.edu.
  15. ^ a b c Althomali, T. (2012, September–December). Management of congenital cataract. Saudi Journal for Health Sciences, 1(3), 115. Retrieved December 5, 2013, from Academic OneFile.
  16. ^ Brian, G., and H. Taylor. "Cataract Blindness -- Challenges for the 21st Century." Bulletin Of the World Health Organization 79.3 (2001): 249-56. Academic Search Complete (OBESCO). Web. <ehis.ebscohost.com.central.ezproxy.cuny.edu>.
  17. ^ Craig, J.E., J.E. Elder, D.A. Mackey, I.M. Russell-Eggitt, and M.G. Wirth. "Aetiology of Congenital and Paediatric Cataract in an Australian Population. (Clinical Science)." British Journal of Ophthalmology 86.7 (2002): 782. Academic OneFile. Web. 5 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA89239993&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=669cf1931b114c0ce141a5f2cee472db>.
  18. ^ Rashad, Mohammad A. "Pharmacological Enhancement of Treatment for Amblyopia." Clinical Ophthalmology 6 (2012): 409. Academic OneFile. Web. 5 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA344827593&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=287826a431f0ee1b743459536bce74c9>.
  19. ^ Althomali, Talal. "Management of Congenital Cataract." Saudi Journal for Health Sciences 1.3 (2012): 115. Academic OneFile. Web. 5 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA317846548&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=a6e914de37a00a55f46b54774cc1bc56>.
  20. ^ Brian, G., and H. Taylor. "Cataract Blindness -- Challenges for the 21st Century." Bulletin Of the World Health Organization 79.3 (2001): 249-56. Academic Search Complete (OBESCO). Web. <ehis.ebscohost.com.central.ezproxy.cuny.edu>.
  21. ^ Morello, C. M. "Etiology and Natural History of Diabetic Retinopathy: An Overview." American Journal of Health-System Pharmacy 64S3-S7 (2007): n. pag. Web. <ehis.ebscohost.com.central.ezproxy.cuny.edu>.
  22. ^ American Diabetes Association. "A1c and Eag." Diabetes.org. N.p., 30 July 2013. Web. <http://www.diabetes.org/living-with-diabetes/treatment-and-care/blood-glucose-control/a1c/>.
  23. ^ Morello, C. M. "Etiology and Natural History of Diabetic Retinopathy: An Overview." American Journal of Health-System Pharmacy 64S3-S7 (2007): n. pag. Web. <ehis.ebscohost.com.central.ezproxy.cuny.edu>.
  24. ^ Morello, C. M. "Etiology and Natural History of Diabetic Retinopathy: An Overview." American Journal of Health-System Pharmacy 64S3-S7 (2007): n. pag. Web. <ehis.ebscohost.com.central.ezproxy.cuny.edu>.
  25. ^ Glaucoma Research Foundation. "High Eye Pressure and Glaucoma." Glaucoma Research Foundation. N.p., 5 Sept. 2013. Web. <http://www.glaucoma.org/gleams/high-eye-pressure-and-glaucoma.php>.
  26. ^ Krader, Cheryl Guttman. "Etiology Determines IOP Treatment: Customized Approach Needed for Managing Elevated Pressure in Patients with Uveitis." Ophthalmology Times 15 May 2012: 24. Academic OneFile. Web. 5 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA294505910&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=e8aa73e119058ee89d879915b9226421>.
  27. ^ Glaucoma Research Foundation. "High Eye Pressure and Glaucoma." Glaucoma Research Foundation. N.p., 5 Sept. 2013. Web. <http://www.glaucoma.org/gleams/high-eye-pressure-and-glaucoma.php>.
  28. ^ Glaucoma Research Foundation. "High Eye Pressure and Glaucoma." Glaucoma Research Foundation. N.p., 5 Sept. 2013. Web. <http://www.glaucoma.org/gleams/high-eye-pressure-and-glaucoma.php>.
  29. ^ Krader, Cheryl Guttman. "Etiology Determines IOP Treatment: Customized Approach Needed for Managing Elevated Pressure in Patients with Uveitis." Ophthalmology Times 15 May 2012: 24. Academic OneFile. Web. 5 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA294505910&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=e8aa73e119058ee89d879915b9226421>.
  30. ^ Meszaros, Liz. "Pediatric, Adult Glaucoma Differ in Management: Patient Populations Not Same, so Diagnosis/clinical Approach Should Reflect Their Uniqueness." Ophthalmology Times 15 Sept. 2013: 11. Academic OneFile. Web. 5 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA348978213&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=543a017fba673f928c486fc78c826e1d>.
  31. ^ Meszaros, Liz. "Pediatric, Adult Glaucoma Differ in Management: Patient Populations Not Same, so Diagnosis/clinical Approach Should Reflect Their Uniqueness." Ophthalmology Times 15 Sept. 2013: 11. Academic OneFile. Web. 5 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA348978213&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=543a017fba673f928c486fc78c826e1d>.
  32. ^ Meszaros, Liz. "Pediatric, Adult Glaucoma Differ in Management: Patient Populations Not Same, so Diagnosis/clinical Approach Should Reflect Their Uniqueness." Ophthalmology Times 15 Sept. 2013: 11. Academic OneFile. Web. 5 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA348978213&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=543a017fba673f928c486fc78c826e1d>.
  33. ^ a b Jabs, D. A., & Busingye, J. (august 2013). Approach to the diagnosis of the uveitides. ScienceDirect OBESCO, 156(2), 228-236. Retrieved from http://www.sciencedirect.com.central.ezproxy.cuny.edu:2048/science/article/pii/S0002939413002158
  34. ^ Rao, Narsing. "Uveitis in Developing Countries." Indian Journal of Ophthalmology June 2013: 253. Academic OneFile. Web. 4 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA336782780&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=a097cc582d61a22b78b358a3209a0355>.
  35. ^ Rao, Narsing. "Uveitis in Developing Countries." Indian Journal of Ophthalmology June 2013: 253. Academic OneFile. Web. 4 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA336782780&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=a097cc582d61a22b78b358a3209a0355>.
  36. ^ Rao, Narsing. "Uveitis in Developing Countries." Indian Journal of Ophthalmology June 2013: 253. Academic OneFile. Web. 4 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA336782780&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=a097cc582d61a22b78b358a3209a0355>.
  37. ^ Rao, Narsing. "Uveitis in Developing Countries." Indian Journal of Ophthalmology June 2013: 253. Academic OneFile. Web. 4 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA336782780&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=a097cc582d61a22b78b358a3209a0355>.
  38. ^ Rao, Narsing. "Uveitis in Developing Countries." Indian Journal of Ophthalmology June 2013: 253. Academic OneFile. Web. 4 Dec. 2013. <http://go.galegroup.com/ps/i.do?id=GALE%7CA336782780&v=2.1&u=cuny_centraloff&it=r&p=AONE&sw=w&asid=a097cc582d61a22b78b358a3209a0355>.
  39. ^ Visual impairment and blindness, (2011). World Health Organization
  40. ^ a b Bosanquet N, Mehta P., P. Evidence base to support the UK Vision Strategy.RNIB and The Guide Dogs for the Blind Association
  41. ^ a b c World Health Organization[full citation needed]
  42. ^ Cupples, M., Hart, P., Johnston, A., & Jackson, A.(2011) Improving healthcare access for people with visual impairment and blindness BMJ (Clinical Research Ed.)
  43. ^ a b c d Bialistock, R. (2005). Towards better communication, from the interest point of view. or-skills of sight-glish for the blind and visually impaired. International Congress Series, 1282, 793-795.
  44. ^ a b c d Jan, James; Freeman, Roger; Scott, Eileen (1977). Visual Impairment in Children and Adolescents. 111 Fifth Avenue New York, NY 10003: Grune and Stratton. p. 17-27 113-121 187-2270. ISBN 0-8089-1010-8. 
  45. ^ Strickling, C.,(2010, October 6). Impact Of Visual Impairment On Development. Texas, USA Texas School for the Blind and Visually Impaired
  46. ^ American Optometric Association web site
  47. ^ Baja Visión, 1999[full citation needed]
  48. ^ a b c Virgili G, Acosta R, Grover LL, Bentley SA, Giacomelli G (2013). "Reading aids for adults with low vision". Cochrane Database Syst Rev 10: CD003303. doi:10.1002/14651858.CD003303.pub3. PMID 24154864. 

External links[edit]