World Sight Day is an annual day of awareness held on the second Tuesday in October. The event is currently led by the International Agency for the Prevention of Blindness under the VISION2020 global initiative. Throughout the world 36 million individuals are blind, and 217 million individuals have a moderate or severe vision impairment (International Agency for the Prevention of Blindness, 2015). In honor of World Sight Day, the New England Consortium on Deafblindness is sharing information regarding three different types of visual impairments.
Cortical Visual Impairment
Cortical Visual Impairment (CVI) is a neurological impairment that affects a child’s vision. This type of visual impairment is caused by damage to any part of the brain that relates to visual processing. Children with CVI do not typically have ocular irregularities, although CVI may be seen with other disorders such as Strabismus. CVI occurs at a high rate among children with multiple disabilities, children with Cerebral Palsy, and children with developmental disabilities.
Diagnosis:
- CVI can be difficult to diagnose due to the lack of ocular irregularities and high rate of additional disabilities.
- The diagnosis of CVI occurs through medical examination and neuroimaging, and the early identification and diagnosis of CVI is integral to early intervention.
Teaching strategies:
- Extended response times, visual AND auditory simplicity, frequent repetition and consistency, and the use of touch cues.
- The use of highly preferred colors (red and yellow), the use of light to create contrast, and limiting the glare from overhead lighting.
Coloboma of the eye
Coloboma of the eye is a defect in the structure of the eye that is present from birth (common in individuals with CHARGE Syndrome). A coloboma is caused when issues occur during the development of the eyeball. Colobomas can occur on one or both eyes and can occur within different parts of the eye including the iris, lens, optic nerve, eyelid, or retina.
Diagnosis:
- Due to the physical nature of the defects, a coloboma is typically identified by a pediatrician visually or during a routine eye exam.
Implications:
- The primary implication of a coloboma is sensitivity to light, however, the impact on a child’s vision is determined by the severity, whether or not it occurs in one or both eyes, and the location of the coloboma.
Curriculum Adaptations:
- Due to the light sensitivity children may require sunglasses, tinted lenses, visors, and/or light covers in soft colors such as purple or blue to combat the harshness of overhead lights.
- Black curtains may be used to cut back on glare in rooms with large amounts of natural light.
- Children may require adaptations such as enlarged text, a magnifying glass, or assistive technology to access the classroom curriculum.
Usher syndrome
Usher Syndrome is a genetic disorder with partial or total hearing loss and vision loss that progresses over time. Infants born with Usher Syndrome are born deaf or with a partial hearing loss, and the loss of vision occurs during childhood or adolescence. Vision loss occurs as progressive loss within the visual field, resulting in tunnel vision. In addition to hearing and vision loss, Usher Syndrome can cause serious balance issues.
Types of Usher syndrome:
- Usher type I: Children are born with balance problems and profound hearing loss/deafness. By age 10, children will begin to have decreased vision at night, and by midlife individuals will present with severe vision loss.
- Usher type II: Children are born with moderate to severe hearing loss. By adolescence, night vision will begin to decrease and by midlife there will be a severe vision loss. Individuals with Usher type II do not typically present with balance problems.
- Usher type III: Children may have progressive hearing loss in their childhood and early teenage years. Vision loss in Usher type III varies in severity and age of onset. Vision issues often occur in the teenage years and progress to severe vision loss by midlife. Normal or near normal balance is typical in childhood, although there is a chance of balance problems in the future.
Educational strategies:
- Due to hearing loss and the progressive loss of vision, programs for students with Usher syndrome should include vocational and mobilityprograms, and academics.
- Classrooms should have comfortable lighting with little glare.
- Rooms should have minimal clutter and furniture should be arranged with the appropriate amount of space for students to navigate as independently as possible.
- Students with Usher syndrome may use a variety of communication methods including spoken word, sign language, and/or tactile cues.
Sources: https://nei.nih.gov/faqs/cortical-visual-impairment-cvi; https://www.tsbvi.edu/component/content/article/132-syndromes/3267; http://www.familyconnect.org/info/after-the-diagnosis/browse-by-condition/coloboma/123
