Eyes and Ears (1) Flashcards
What structure is damaged in noise-induced hearing loss?
Cochlea
* the hearing loss is likely to be temporary but repeated or severe damage can cause permanent hearing loss
What structure is most likely involved in the presence of symptoms of ‘world spinning around’ ?
Fluid (endolymph) within semi-circular canal moves around -> spinning sensation
What is the danger of use of cotton budts?
Damage to the tympanic membrane -> perforated eardrum -> may heal over time
What structure is involved in ‘glue ear’?
Build up of fluid in the middle ear -> otitis media with effusion
SImple pathway of vision (from light entering the eye)
Light -> cornea -> lens -> viterous humour -> rods + cons (retina) -> optic n. (CN II) -> visual cortex (occipital lobe)
Simple pathway of sound -> hearing (start from sound wave)
sound wave -> pinna -> auditory cannal -> middle ear* -> hair cells (Organ of Corti on Cochlea) -> vestibulochochlear n. (CN VIII) -> auditory cortex
*middle ear structures: tympanic membrane, airspace and ossicles: malleus, incus and stapes
What allows the outflow/ drainage of aqueous humour?
Contraction of the ciliary muscle -> opens the Trabecular meshwork -> outflow of Aqueous Humour through the Canal of Schlemm
What’s keratitis?
(4) symptoms
Keratitis
- inflammation of the cornea
Symptoms: painful, red eye, photophobia, profuse tearing
What’s retinitis pigmentosa?
Retinitis pigmentosa
- inherited condition
- progressive degeneration of photoreceptors
- initially rods, then cones
Ambylopia
- other name
- simple pathophysiology
- age
- cause
Amblyopia = lazy eye
- failure of neural connections between brain and eye to develop properly
- development happens in first 7-8 years of life – older than that may never develop proprly even if underyling eye problem is corrected.
- Causes - anything which means one eye is used less than the other (squint, cataract)
What happens if a yound child (up to 5 years)is deaf?
Childhood deafness
- young children, up to 5 years or so, who are deaf will not develop normal neural pathways (just like amblyopia)
- even if their hearing is improved (eg cochlear implant) they may still not be able to hear / interpret speech and sounds
What are the elements of the examination of the eye? (7)
- Look at the eye
- Evert upper lid (if suspect foreign body)
- Visual acuity (Snellen chart) -> with and without usual glasses / lenses
- Pupils Equal and Reacting to Light and Accommodating? (PERLA)
- Red reflex
- Fundi (fundoscopy)
- Visual fields
How to test for visual acuity?
Standard Snellen chart for use at 6 m
What instructions to give to the patient while using Snellen chart?
Instructions:
- Cover one eye
- Read the lowest line that you can read
- Any mistakes -> try the line above
How to note the results of the Snellen chart?
VA = 6/ n (n = number just above the lowest line they read correctly)
- Top number = distance (in metres) at which the test chart was presented (usually 6m)
- Bottom number = position on the chart of the smallest line read by the ‘patient’
Example: 6/60 means the subject can only see the top letter when viewed at 6m
- How does the ‘pin hole’ test work?
- What’s its purpose?
The pin hole removes any refractive error because you only see light that passes straight through the pin hole and lens to the retina – so no refraction is needed
What’s Limbus?
Limbus = junction of the cornea and sclera
Which eye is it (R of L)? Why?
Right eye - macula in the middle and the optic disc at the nasal side