Visual Impairments

Visual Impairments By Lacey Curtis EDN 410 November 14, 2009

visual impairments defined The term Visual Impairment describes any kind of vision loss whether it’s a person who cannot see at all or someone who has partial vision loss Visual impairments are usually defined by legal or educational standards. The terms legal blindness, total blindness, partially sighted, and low vision are all legal terms used to refer to visual impairments. From an educational viewpoint, the term visual impairment is defined less by visual acuity and more by educational tasks such as reading. Functional vision is another educational term which refers to the way a person uses their vision as well as the amount of vision that person has. http://kidshealth.org/teen/diseases_conditions/sight/visual_impairment.html Teaching Students Who Are Exceptional, Diverse, & At Risk

Definitions continued… • Legal Blindness describes a person who has less than 20/200 vision in their best eye or a very limited field of vision (20 degrees at its widest point). • Total Blindness refers to a small group of individuals with visual impairments who are unable to see anything, including objects or light sources. • Partially Sighted is a phrase that was formerly used to describe individuals with a visual acuity in the range of 20/70 to 20/200. This term is not presently used as widely as it once was. • Low Vision is the present term typically used for individuals with visual acuity in the range of 20/70 to 20/200. These individuals continue to have difficulty with vision even with corrective lenses (glasses). http://www.nichcy.org/Disabilities/Specific/Pages/VisualImpairment.aspx Teaching Students Who Are Exceptional, Diverse, & At Risk

Normal eye anatomy http://www.lensdoctors.net/eye-health/eye-anatomy.html

Anatomy of eye continued… • IRIS: Pigmented tissue lying behind cornea that (1) gives color to the eye, and (2) controls amount of light entering the eye by varying size of black pupillary opening; separates the anterior chamber from the posterior chamber. • CORNEA: Transparent front segment of the eye that covers iris, pupil, and anterior chamber, and provides most of an eye's optical power. • PUPIL: Variable-sized, circular opening in center of iris; it appears as a black circle and it regulates the amount of light that enters the eye. • LENS: Natural lens of eye; transparent intraocular tissue that helps bring rays of light to focus on the retina. • SCLERA: The white of the eye; a protective fibrous outer layer covers all of the eyeball except for the part covered by the cornea. • CILIARY BODY: A muscular ring under the surface of the eyeball; helps the eye focus by changing the lens’s shape and also produces aqueous humor. • CHOROID: The vascular layer between the sclera and the retina; the blood vessels in the choroid help provide oxygen and nutrients to the eye. • OPTIC NERVE: Largest sensory nerve of the eye; carries impulses for sight from retina to brain. • MACULA: Small, specialized central area of the retina responsible for acutecentral vision. • RETINA: Part of the eye that converts images into electrical impulses sent along the optic nerve for transmission back to the brain. Consists ofmany named layers that include rods and cones. • VITREOUS: Transparent, colorless, gelatinous mass; fills rear two-thirds of the interior of the eyeball, between the lens and the retina. http://www.lensdoctors.net/eye-health/eye-anatomy.html

A few terms explained… • Visual acuity: This is the measurement of how clearly we see. A child’s acuity is measured in each eye individually and in both eyes working together. A loss of acuity can range from mild to severe and differ in both eyes. Glasses may be prescribed to help improve visual acuity. • Visual field: This is the total area that can be seen without moving the head or eyes. A loss of visual field can occur on one side (hemianopsia) or on the upper or lower field. While others may experience spots of poor vision (scotomas) within their visual field. With some eye conditions, a loss of peripheral vision (tunnel vision) or a central visual field loss is present. http://www.nhbvi.com/Agenda/Goal1/Book1/typesanddegrees.html

Types of visual impairments:Refractive errors • Myopia (Nearsightedness): The image of a distant object does not focus on the retina but instead in front of it, which makes it appear blurry. This can result from having an elongated eyeball, a lens that is too strong, or a cornea that is excessively curved. The child can see things that are near but not farther away. • Hyperopia (Farsightedness): The image focusing point is behind the retina which results in straining to focus correctly, especially at close distances. This can result from shortness of the eyeball, a lens that is weak, or a cornea that is mostly flat. The child can see things well at a distance, but not up close or near. • Astigmatism: This error occurs when the cornea has a cylindrical curvature which prevents light rays from focusing on one point on the retina. This results in both near and far objects sometimes appearing blurry. Astigmatism often occurs in conjunction with Myopia and Hyperopia. http://www.nhbvi.com/Agenda/Goal1/Book1/commoncauses.html

Types of visual impairments:Ocular motor impairment Ocular motor impairment occurs when a child has difficulties with the muscles controlling the eyes. Eye muscles control how well a child is able to fixate, follow, search, and converge with their eyes. As the muscles work together, the child is able to see three dimensional images. Surgery is an option to help a child with ocular motor difficulties. http://www.nhbvi.com/Agenda/Goal1/Book1/typesanddegrees.html

Types of visual impairments:eye Conditions • Albinism: This is an inherited condition in which the individual has decreased pigment that causes abnormal optic nerve development. As well as having a decreased visual acuity, these children may also be sensitive to light. Tinted lenses, glasses and low vision aids can all help to decrease light sensitivity and maximize vision. • Amblyopia (lazy eye): A weakening of the image of one eye typically due to that eye having a much poorer acuity or being turned in or out. These children may have some functional field of vision loss and poor or no depth perception. Placing a patch on the stronger eye and using glasses may be prescribed. • Cataracts: Characterized by opacity or cloudiness of the lens. Vision is affected since light is unable to pass through the lens. Some cataracts get worse with time while others remain unchanged. Cataracts can occur in one eye (unilateral) or both eyes (bilateral). These children may have blurry vision, poor color vision, light sensitivity, reduced visual acuity, or nystagmus. Surgery is sometimes recommended to remove cataracts depending on how severe they are. • Coloboma: This is a birth defect that causes a cleft in the pupil, iris, lens, retina, choroid, or optic nerve. This condition can result in reduced acuity and field of vision loss if the damage extends to the retina. http://www.nhbvi.com/Agenda/Goal1/Book1/commoncauses.html

Types of visual impairments:eye Conditions continued… • Glaucoma: A condition which is characterized by increased pressure in the eye caused by blockage of normal flow of fluid in the eye. Changes in pressure can cause the child with glaucoma’s vision to fluctuate. Glaucoma may also cause peripheral field loss, poor night vision, and sensitivity to light. If glaucoma goes untreated, damage to the optic nerve can result. • Nystagmus: Involuntary movement of the eye which can be horizontal, vertical, circular or a combination. A child with nystagmus has a hard time maintaining fixation on objects since their eyes are frequently moving. This results in reduced visual acuity and fatigue. By turning the head or eyes to a certain position known as the “null point”, nystagmus can be minimized. This “null point” is different for each person. • Optic Nerve Atrophy: When damage or degeneration to the optic nerve which carries visual signals to the brain takes place, this condition occurs. Depending on the severity of the damage, vision loss varies and may include blurred vision, poor color and night vision, and sensitivity to light. • Optic Nerve Hypoplasia: Sometimes the optic nerve under develops while a fetus is in utero, which results in a small optic nerve and visual impairment. The degree of visual impairment can vary significantly, but there is typically acuity loss. This condition is sometimes associated with other conditions. http://www.nhbvi.com/Agenda/Goal1/Book1/commoncauses.html

Types of visual impairments:eye Conditions continued… • Retinitis Pigmentosa (RP): A hereditary and degenerative condition of the retina which results in loss of peripheral vision or “tunnel vision”. The condition usually starts with difficulty in seeing in dimly lit areas and progresses to significant visual impairment. • Retinoblastoma: In this condition, a cancerous tumor grows on the retina. Aggressive treatment of all tumors through laser, radiation, and/or chemotherapy is required. As retinoblastoma progresses, an enucleation or removal of the eye is sometimes needed. If an eye is removed, the child will lose their depth perception. • Retinopathy of Prematurity (ROP): A condition common in children who were premature infants and required high concentrations of oxygen at birth. As the normal development of the blood vessels of the retina is interrupted, scarring and detachment of the retina can result. The child with ROP may have a decreased visual acuity and refractive errors. • Strabismus: In this condition, a muscle imbalance prevents both eyes from being able to look directly at an object at the same time. Different types of strabismus include: esotropia (an inward turn), exotropia (an outward turn), hypertropia (an upward turn), and hypotropia (a downward turn). http://www.nhbvi.com/Agenda/Goal1/Book1/commoncauses.html http://www.brighthub.com/education/special/articles/35103.aspx

Types of visual impairments:cortical Cortical visual impairment or Neurological visual impairment (NVI) is not caused by damage or a condition of the eye. Instead, it is caused by damage to the visual cortex of the brain which processes visual information. The vision loss can be mild or severe, and can also vary from day to day. Cortical visual impairment may be temporary or permanent. Children with a cortical visual impairment may also have cerebral palsy, seizure disorder, and developmental delays as a result of the damage to the brain. People with this type of impairment may have trouble recognizing faces, interpreting drawings, perceiving depth, or distinguishing between background and foreground. http://www.nhbvi.com/Agenda/Goal1/Book1/commoncauses.html http://www.afb.org/Section.asp?SectionID=40&DocumentID=2139

Prevalence of visual impairments • Simple refractive errors (nearsighted, farsighted, astigmatism) make up the majority of common visual impairments. • More boys than girls are visually impaired. • The rate at which visual impairments occur in individuals under the age of 18 is 11.2 per 1,000. • Severe visual impairments (legally or totally blind) occur at a rate of .06 per 1,000. • Many visual impairments can occur at any age, however, over two-thirds of those with visual impairment are over age 65. http://www.napcse.org/exceptionalchildren/visualimpairments.php http://www.brighthub.com/education/special/articles/35103.aspx

Strategies for teaching • In order to assist students with visual impairments get through printed material in class, you will need a combination of materials. Books in Braille, readers, and recorded books and class lectures will all help. • Modify assignments when possible in order to allow students to become more independent. • Teach other students how to help guide the student with a visual impairment. • Encourage students with visual impairments to use their sense of touch, and provide tactile models when possible. • Describe people and happenings in the classroom verbally for the visually impaired student. • If possible, assign a peer “visual translator” to work with the visually impaired student. The visual translator verbally describes visual images to the student to assist in their learning. http://glencoe.com/sec/careers/teacher/strategies.shtml#f

Udl and d.i. • A nonprofit research development organization entitled CAST (Center for Applied Special Technology) has been researching Universal Design of Learning since 1984. • UDL provides a blueprint for creating flexible goals, methods, materials, and assessments that accommodate learner differences. • "Universal" does not imply a single optimal solution for everyone. Instead, it is meant to underscore the need for multiple approaches to meet the needs of diverse learners. • Embedded features that help those with disabilities eventually benefit everyone. UDL uses technology's power and flexibility to make education more inclusive and effective for all. • When using the approach of Differentiated Instruction, it is important to provide different approaches in process, product, and content. www.cast.org

Udl and d.i. continued… • CAST has a software program titled CAST eReader available for schools to install to assist standard students as well as learning disabled students. Within this program is a function called eTrekker which helps students to organize their Web searches. The student types in a search question and eTrekker checks their spelling and identifies search terms to use from the question. After the list of 10 websites comes up, the student can select a site and click on “read” to have the information read aloud to them. The program saves the research question, key terms, websites visited, and any notes created by the student using the onscreen notepad. With some assistance, this program could really benefit the visually impaired student, as well as be functional for the standard student. http://techplan.org/ci2005/udl_def_and_examples.pdf

Sources for teachers • Teaching computer skills to visually impaired children: A concept based approach http://www.tsbvi.edu/technology/computer-skills.htm • Council for Exceptional Children: The voice and vision of special education http://www.cec.sped.org • Visual impairments and Multiple impairments http://www.tsbvi.edu/recc/mivi.htm

Resources • Textbook Teaching Students Who Are Exceptional, Diverse, & At Risk • http://www.nichcy.org/Disabilities/Specific/Pages/VisualImpairment.aspx • http://kidshealth.org/teen/diseases_conditions/sight/visual_impairment.html • http://www.nhbvi.com/Agenda/Goal1/Book1/commoncauses.html • http://www.lensdoctors.net/eye-health/eye-anatomy.html • http://www.brighthub.com/education/special/articles/35103.aspx • http://www.afb.org/Section.asp?SectionID=40&DocumentID=2139 • http://www.napcse.org/exceptionalchildren/visualimpairments.php • http://glencoe.com/sec/careers/teacher/strategies.shtml#f • www.cast.org • http://techplan.org/ci2005/udl_def_and_examples.pdf

Visual Impairments