18ECO124T - HUMAN ASSIST DEVICES UNIT 2 & 3 - 4M

 4M:


Describe about the audiometric masking Techniques

Interaural attenuation:

  • IA is the amount of sound that is attenuated/reduced when crossing from one ear to the other

  • The IA varies

  • Depending on the frequency 

  • From patient to patient

  • Depending on the transducer used

  • IA of air conduction - headphones:

  • Minimum IA of air conduction - headphones is 40 db HL

  • If we present 80db to test ear, 40 db of that sound is reaching the cochlea of the non-test ear

  • IA of air conduction - inserts:

  • Minimum IA of air conduction - inserts is 70 db HL

  • If we present 80db to test ear, 10 db of that sound is reaching the cochlea of the non-test ear

  • IA of bone conduction:

  • Minimum IA of bone conduction is 0 db HL

  • If we present 30db to test ear, 30 db of that sound is reaching the cochlea of the non-test ear


What is meant SISI? Explain about the SISI scores in hearing aid.

  • SISI - Short Increment Sensitivity Index

  • Patients with cochlear lesions distinguish smaller changes in intensity of pure tone better than normal person

  • In this test, continuous tone is presented 20db above the threshold and sustained for about 2 min

  • Every 5s, tone is increased by 1db and 20 such blings are presented

  • Patient indicates the bling heard

  • SISI scores:

  • CHL: 15%

  • Cochlear deafness: 70-100%

  • Nerve deafness: 0-20%


Distinguish between ITC and CIC in hearing aid.

  1. ITC (In-The-Canal) Hearing Aids:

    • Slightly larger than CIC hearing aids.

    • Remain discreet but may be more visible than CIC devices.

    • Suitable for people with mild to moderate hearing loss.

    • Speaker (receiver) is placed in the ear canal.

    • May offer Bluetooth streaming connection using compatible devices.

  2. CIC (Completely-In-The-Canal) Hearing Aids:

    • Almost completely hidden in the ear canal.

    • Smaller and more unobtrusive than ITC hearing aids.

    • Ideal for people with mild to moderate hearing loss and normal ear canal size.

    • Due to their small size, CIC hearing aids generally do not have smartphone or Bluetooth connectivity options.

    • Requires careful handling when removing from the ear due to the speaker wire placement behind the ear.


Explain the functions of Sclera and Pupil in anatomy of eye.

Sclera:

  • White outer layer of the eyeball

  • Tough, fibrous membrane that helps to maintain the spherical shape of the eyeball

  • Parts: 

  • Cornea

  • Canals of schlem

  • Conjuctiva 

Choroid layer:

  • Middle layer of the eye

  • Supply blood vessels to the eye and contains dark pigment granules that prevent reflection of light in the eye

  • Parts: 

  • Ciliary body

  • Iris

  • Pupil 

  • Pupil - rounded opening of the iris through which light passes


Describe about the middle layer of hearing mechanism.

Middle ear:

  • Function: adaptation regarding physical media between ear canal and inner ear

  • Low sound pressure and high particle velocity at the eardrum

  • High pressure and low particle velocity at inner ear

  • Force transformation ratio 1:90

  • Pressure transformation ratio 1:22

  • Surface ratio 50:3

  • Ossicles: hammer, anvil and stirrup


Differentiate bone conduction and air conduction?

Bone conduction:

  • When there is a 15db or more difference between the air conduction threshold of the test ear and the bone conduction threshold of the same ear, then mask for bone conduction

  • Minimum IA of bone conduction is 0 db HL 

Air conduction:

  • When there is a 40db or more difference between the air conduction threshold of the test ear and the bone conduction threshold of the non-test ear, then mask for air conduction - headphones

  • When there is a 70db or more difference between the air conduction threshold of the test ear and the bone conduction threshold of the non-test ear, then mask for air conduction - inserts

  • Minimum IA of air conduction - headphones is 40 db HL

  • Minimum IA of air conduction - inserts is 70 db HL


Describe about the components of hearing aid.

  • Microphone: receives sound and converts into electrical impulses

  • Amplifier: intensifies electrical impulses

  • Receiver: translates those electrical impulses into louder sounds

  • Battery: serves as power source for device

  • Earmolds: directs the flow of sound into the ear and enhance sound quality


Explain the functions of Rods and cones in anatomy of eye.

Retina: 

  • Innermost layer of the eye

  • Contains photoreceptors

  • Photoreceptors - Cells responsible for converting light into nerve impulses - rods and cones

Rods:

  • Cylindrical photoreceptors found in greatest concentration on the edges of the retina

  • Most common type of receptor

  • Allow us to see in low light and provide for peripheral vision

Cones:

  • Conical photoreceptors found in greatest concentration near the center of the retina

  • 3 varieties of cones, each sensitive to a particular wavelength of light - blue, green and red

  • Allow for visual acuity and color vision


What are the types of Visual Impairments? 

Types of visual impairments:

  • Hyperopia: far sightedness

  • Myopia: near sightedness

  • Astigmatism: cannot focus at one object regularly

  • Color blindness: decreased ability to differentiate between colors

  • Retinopathy of prematurity: scarring and detachment of retina

  • Macular D generation: loss of central vision

  • Glaucoma: deficiency in formation of eyes

  • Diabetic retinopathy: total blindness

  • Cataract: cloudy, distorted vision

  • Crossed eye: cannot focus at one object with both eye

  • Coloboma: serious impairment

  • Amblyopea: one eye vision loss

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