1. SPED 537 ECSE Methods Multiple Disabilities Chapter 4 March 13-14, 2006 Deborah Chen, Ph.D. CSU, Northridge

2. Incidence of Visual Impairments 1 in 3000 children 46% congenital 38% vision loss in 1 st year of life 25 % totally blind 25 % light perception 50% functional vision

3. Definitions Legally blind Totally blind Light perception Form perception Partially sighted Low vision

4. Types of Visual Impairment Decreased visual acuity Field loss Loss of contrast sensitivity Color blindness Ocular-motor problems Cortical visual impairment Delayed visual maturation

5. Causes of Acuity Loss Retinopathy of Prematurity Cataracts Nystagmus Refractive errors Strabismus

6. Refractive Errors Myopia Hyperopia Astigmatism

7. Strabismus Esotropia Exotropia Hypertropia Hypotropia

8. Clinical Vision Tests: Fixation and Eye Alignment Versions Hirshberg Krimsky Unilateral and alternating cover test Base-out prism

9. Clinical Vision Tests Pupillary response Vestibular ocular reflex (VOR)- similar to Optokinetic Nystagmus (OKN) test Refractive Error

10. Behavioral Tests Contrast sensitivity Color vision Depth perception Visual fields Visual acuity (Teller Cards)

11. Electrophysiological Tests Visual Evoked Potential (VEP) or Visual Evoked Response (VER) Electroretinography (ERG)

12. Checking for Ocular Health Examines the front and back structures, retinal, optic nerve

13. Ocular Visual Impairment Atypical eye exam Consistent visual attention Nystagmus Restrictions of visual fields Occasional photophobia Eye pressing Occasional head shaking Light gazing

14. Cortical Visual Impairment Normal eye exam Variable vision Short visual attention No nystagmus No head shaking No eye pressing Light gazing Photophobia in 1/3 cases ( Dr. J. Jan, Children’s Hospital, Vancouver, B.C. Canada)

15. Visual Responses Awareness Attention Understanding Fixation Tracking Peripheral Central Simple Complex

16. Visual Responses Awareness Attention Understanding Large Small Familiar Unfamiliar Near Far

17. Visual Stimuli Preferred: Objects with lights or movement Geometric designs High contrast materials Bright colors Familiar: Family members Clothing, utensils, household items Toys Pictures

18. Visual Saliency Motivation factors Lighting (natural, indoor, outdoor, dark) Position (placement of target) Distance from child Highlight or contrast Illumination of target Characteristics of target