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The eye is the sensory organ of the visual system - rather like a camera that takes a picture. For sight, not only a healthy eye but also the vision pathways in the brain and the higher brain functions need to be functioning correctly, rather like the cables attaching a camcorder to a TV monitor. If this cabling is defective, however good the camera a poor signal will be received by the monitor. Even if there is a good picture on the monitor, it may not always be understood properly. This requires learning and other inputs such as sound, touch and experience. To many people 'blindness' is the complete lack of any sight - a black screen - however most people with severe vision impairment who are registered as 'blind' do have some useful vision. Some can even see to read but cannot walk around easily as they have extreme tunnel vision. Others can navigate skilfully but have great difficulty in recognising even familiar faces and in reading even very large print. Some people are born with their vision impairment and in others the problems develop in childhood or even only in later life. There are various categories of visual impairment: 1. Those where the structure of the eye or of the vision pathways is abnormal from birth. Examples include colobomas/microphthalmos (small eye, see coloboma) and anophthalmos (absent eye, see anophthalmia) where the structure of the eye is malformed due to arrest in eye development before birth. The vision pathways may be similarly underdeveloped in optic nerve hypoplasia. In some cases the cause is a defect in the genes which code for the structure of the vision system and in others the damage may be from an infection or other insult to the fetus such as a drugs or toxins taken in by the mother. 2. Those where the vision system is damaged by an illness: for example in cerebral palsy the vision part of the developing brain is especially sensitive to lack of blood flow and oxygen. The developing retina may be damaged in premature infants by a variety of factors leading to retinopathy of prematurity. The teenage or adult retina may be damaged as part of more general damage to blood vessels in diabetes mellitus. Brain tumours may press on the vision pathways in the brain. Tumours may occur in the eye itself and in some cases there is a genetic tendency to develop these tumours particularly in retinoblastoma. In some conditions inflammation of the eye may be part of a more extensive disease such as in some severe childhood forms of arthritis (see Arthritis (Juvenile Idiopathic)) in which the eye is damaged as well as the joints. Some times the drugs needed to treat disease may also damage the eye or vision system. 3. The eye and vision system may be normal or appear normal structurally at birth but lose sight either quickly or slowly due to degeneration of part of the eye - often the retina. This may be due to a genetic defect in the proteins need to maintain health of the retina and vision pathways. Examples of this include the retinal dystrophies including Leber's Congenital Amaurosis and retinitis pigmentosa. Other examples include some optic atrophies and Leber's Hereditary Optic neuropathy. Prevention of blindness and reversal of visual impairment is often not possible. However, many dissimilar disorders do lead to similar functional problems and there are strategies for helping the individual make best use of residual sight, educate others about their requirements and difficulties and aid them with coping with blindness. Visual impairment has not only an impact upon the individual but, particularly if the cause is genetic, upon the family. Inheritance patterns Prenatal diagnosis Medical text written August 2001 by Miss Isabelle Russell-Eggitt FRCS FRCOphth, Consultant Ophthalmic Surgeon, Great Ormond Street Hospital, London, UK.  Support Groups for children and families: Vision Aid Vision Aid is a National Registered Charity No. 518641, established in 1984. It aims to offer practical help and advice to the families of vision impaired children throughout the UK. Children with additional needs are also welcome. The range of free services include: resource centre; guidance on education and benefits; a range of publications; library service for toys and books; weekly drop-in sessions; parent-to-parent contact; visual stimulation programmes; and equipment loan. The organisation also offers advice to professionals working with vision impaired children. The Group is in contact with 5,000 families nationwide. Group details last confirmed June 2007. LOOKLOOK LOOK is a National Registered Charity No. 1007282, established in 1991. It is an umbrella organisation for groups concerned with visual impairment in children. It offers the opportunity for parents and parent support groups to co-operate in order to enhance the education, welfare and leisure opportunities for visually impaired children. It publishes a quarterly newsletter. Group details last confirmed August 2007. VICTA CHILDREN LTDVicta Children Ltd Visually Impaired Children Taking Action (VICTA) is a National Registered Charity No. 1065029, established in 1987. It will consider grant applications for individual children for equipment/services that will aid their education or social skills. VICTA will also consider grant applications from groups and charities supporting visually impaired children. Please contact VICTA for more information. Group details last updated October 2007. NATIONAL BLIND CHILDREN'S SOCIETYNational Blind Children's Society The Society is a National Registered Charity No. 1051607, established in 1996. It offers services for children and young people with a visual impairment, from birth to the completion of full time education. NBCS provides family support, educational advocacy, IT advice and support, and CustomEyes large print children's books. NBCS can provide grants for computers, speech and magnification software, educational toys etc. Group details last updated January 2007. Support Groups for adults and children:
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Contact a Family may also be able to help with information and contacts for conditions not listed - please call the Contact a Family Helpline on 0808 808 3555 Freephone for parents and families (Mon-Fri, 10am-4pm & Mon, 5.30-7.30pm). |
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| This Web Site © Copyright, Contact a Family 2007. Although great care has been taken in the compilation and preparation of this work to ensure accuracy, Contact a Family cannot accept responsibility for any errors or omissions. Any medical information is provided for education/information purposes. It should be noted that most information written about specific disorders includes the most severe scenario. Many individual cases may not display all the features mentioned and the degree of severity of the features that are displayed may vary a great deal between individual cases. You should obtain further information from your medical practitioner. Any links to external websites have been carefully selected but are provided without any endorsement of the content of those sites. Please refer to our detailed Legal page for more information. Contact a Family, 209-211 City Road, London EC1V 1JN Tel: (020) 7608 8700. Registered Charity No. 284912. Company limited by guarantee, registered in England and Wales No. 1633333. HM Revenue & Customs charity tax reference No. XN54769. VAT Reg. No. GB 749 3846 82. |
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