Hearing and Vision

1. Hearing and Vision Development of Young Children with Disabilities#872.514 (61)Carol Ann Heath

2. HEARING Through hearing we perceive and understand our surroundings, we communicate, and we learn.

3. Sound • Pattern of vibrations • Waves have both a frequency or pitch and an intensity • Closer the waves, higher the frequency • Number of cycles per second (top to top)

4. Hearing Loss • Types of Hearing Loss • conductive • sensorineural • mixed

5. Categories of Severity • Normal –can distinguish sound intensities of 20 dB or less • Mild –cannot hear a sound between 25-45 dB • Moderate –cannot hear a sound between 45-70 dB • Severe –cannot hear a sound between 70-90 dB • Profound –greater than 90 dB

6. Type • Unilateral loss • One ear • Less severe • Less than 20% of hearing impaired children • Bilateral loss – both ears

7. Causes • > 50% unknown • Mild-moderate conductive (most common) • Result from chronic otitis media • Middle ear infection • 12% of all children have a middle ear infection • Cleft palate results in ear infections • Transient loss due to noise pollution

8. Severe sensorineural loss • 50% due to genetically inherited condition • 70 types of hereditary deafness • Autosomal recessive disorders • Teacher Collins syndrome • Waardenburg syndrome • Laurence-Moon-Biedl syndrome • Usher syndrome

9. Some severe losses are acquired • Intrauterine infection (rubella, toxoplasmosis, herpes, cytomegalovirus) • Anoxia during delivery • Infant infections & antibiotics used • Head trauma

10. Incidence • Occurs in approximately 0.5% of the population • 40% have a mild loss • 20% have a severe loss • 20% have a profound loss • 1/1000 children • 65% born deaf • 12% develop deafness during first 3 years of life

11. Hearing Milestones • Hearing mechanism is functional by 20 weeks gestation • Newborn will: • Suck preferentially to voice of mother • Will awaken to loud voice of parent • Prefers to listen to speech

12. By 2 months infant can distinguish vowel from consonant sounds • By 4 months infant shows speech pattern preference • By 5 months speech is not influenced by what infant hears (babbling sounds alike worldwide)

13. Identification • Often delay in diagnosis • Reported age of congenital hearing loss of severe to profound in under 6 mos to 18 months • Early development is nonverbal and used prelinguistic communication • Universal infant hearing screen

14. Formal Testing • Performed to: • Determine whether there is a hearing loss • Differentiate a conductive from a sensorineural loss • Determine the configuration of the loss in each ear • Estimate the clarity with which speech sounds can be discriminated

15. Vision • Vision is important to understanding of the world • Blindness causes delays in walking, talking, and dependence on others

16. The Eye • Reflected rays of light from an object strike the eye and are refracted at the surfaces of the cornea and the lens • Refractions yields an image on the retina • Transmitted to the occipital lobes of the brain and is interpreted

17. Development of the Eye • In the fetus, the eyes first appear at 3 weeks of gestation as two bulbs at the side of the head • Hollow out to form the optic cups, then the iris, the lens, and the cornea • By 7 wks, the embryo is only one inch but the eyes are in their basic form • The eyes move from the side of the head to the center of the face

18. Diseases of the Eye • The cornea • The lens • The retina • The optic nerve • The eye muscles

19. Development of Visual Skills • Newborn can distinguish colors, focus on an object, and follow the movement of a face 90% across the visual field • By 1 month, a child can follow an object horizontally • By 2 months can follow the object vertically and imitate a smile • At 3 months, follow an object in a complete circle • At 4 months can reach and grab an object • By 6 months, 20/20 visual acuity

20. Testing Vision • Young infants –measure an optiocokinetic response; done by twirling a cylinder with blk & wh strips; if eye does not move serious vision problem • 6 to 12 mos –rolling balls down an incline to see if child follows movement; use different sized pictures of toys • Older children –Snellen eye chart

21. Blindness • Legal blindness • Defined as visual acuity of less than 20/200 despite correction • Partially sighted • 20/70 to 20/200 with correction

22. Incidence • Overall incidence is .4/1000 • 46% born blind • 38% loss sight < 1 yr

23. Levels • 25% totally blind • 25% have some light perception • 50% use large type

24. Causes • Most common causes are prenatal viral infections and eye malformations • At birth, retrolental fibroplasia (RLF), trauma, infections, and tumors

25. Development • May be an isolated disability or part of a multiple disability • Notice abnormalities in eye movement; eyes may be jerky, uncoordinated, not focus or follow objects • Even with normal intelligence, may have early developmental delays

26. Interventions • Large print books • Braille • Early intervention • Mobility training • Environmental modifications