Quick questions on Technologies for hearing and vision disorders: HSC Biology Module 8

Conductive hearing loss. Sound transmission through the outer or middle ear is blocked or reduced. Causes include ear wax, otitis media, perforated eardrum and otosclerosis (ossicle stiffening).

Hearing aids. Amplify incoming sound. Modern digital hearing aids have a microphone, amplifier, speaker (receiver) and battery, with software that selectively amplifies speech frequencies and suppresses background noise. Effective for mild to moderate hearing loss where hair cells still function.

Sound transmission through the outer or middle ear is blocked or reduced. Causes include ear wax, otitis media, perforated eardrum and otosclerosis (ossicle stiffening).

Damage to the cochlear hair cells or auditory nerve. Causes include age-related (presbycusis), noise exposure, ototoxic drugs (some antibiotics, cisplatin) and genetic conditions.

Both conductive and sensorineural components.

Used for conductive loss when the outer or middle ear is non-functional. A titanium implant in the skull conducts sound vibrations through bone directly to the cochlea, bypassing the middle ear.

Used for severe to profound sensorineural hearing loss. Components and mechanism are described in the past-question answer above. The implant bypasses damaged hair cells by directly stimulating the auditory nerve through an electrode array in the cochlea.

A small actuator attached to the ossicles vibrates them mechanically. Used when conventional hearing aids cause feedback or skin reactions.

Eye too long or cornea too curved; light focuses in front of the retina. Distant objects are blurred. Highly prevalent and rising; almost half of young adults globally.

Eye too short or cornea too flat; light would focus behind the retina. Near objects are blurred.

Irregular cornea curvature; light focuses at multiple points. Causes blurred or distorted vision.

Age-related stiffening of the lens; the eye loses the ability to accommodate for near vision. Begins around age 40 to 45.

Opacification of the natural lens, scattering light. Common with age, also caused by diabetes, UV exposure and steroid use.

Degeneration of central retinal photoreceptors. Leading cause of blindness in older Australians.

External refracting lenses placed in front of the eye. A concave (negative power) lens diverges light to correct myopia; a convex (positive power) lens converges light to correct hyperopia; a cylindrical lens corrects astigmatism; multifocal or progressive lenses correct presbyopia.