Eyes and ears (3) Flashcards
What’s:
- amblyopia
- ametropia
- Amblyopia: uncorrectable poor vision without a structural abnormality.
- Ametropia: refractive error so eye is unable to make light focus on retina. (Includes myopia and hypermetropia)
What’s:
- anisometropia
- anisocoria
- Anisometropia: large difference in refractive errors between eyes.
- Anisocoria: unequal sized pupils.
What’s astigmatism?
Astigmatism: eye’s optical system cannot produce a point of focus because of irregular shape of cornea -> so horizontal/vertical planes do not all coalesce at a single point on retina
*Can usually correct with cylindrical lens.
What’s:
- emmetropia
- hypermetropia
- myopia
- Emmetropia: normal eye, with light focusing on retina.
- Hypermetropia (or hyperopia) (long-sightedness) where light is focused behind retina
- Myopia (short-sightedness), where light is focused in front of retina (causing blurry distance vision)
What’s:
- keratoconus
- presbyopia
- Keratoconus: progressive thinning of the cornea; rare cause of myopia and astigmatism: best corrected by rigid contact lenses
- Presbyopia: lens less flexible because of age-related changes. Unable to do close-up tasks (e.g. reading)
Is raised pressure (and how much) suggestive of glaucoma?
- Approx 50% all glaucoma have normal IOP.(< 21mm Hg)
- Approx 10% population (without glaucoma) have IOP ≥ 21 mmHg. (= ocular hypertension)
Raised IOP is risk factor for glaucoma. Glaucoma ≠ raised IOP. Raised IOP ≠ glaucoma.
Difference in pathophysiology of closed vs open- angle glaucoma
Closed angle (rare) = trabecular network (irido-corneal angle – where aqueous flows out between iris and cornea) is blocked -> painful red eye, loss of vision, often sudden
Open angle (common) = meshwork not blocked but there is still not free flow through it and IOP rises (or not!)
Closed angle glaucoma - symptoms and what can trigger an attack
Symptoms
- severe pain in eye, often around eye and frontal headache
- Blurred vision, coloured haloes around lights (can get in mild, subacute attacks).
- Malaise (nausea, vom).
- Attack precipitants – mid-dilated pupil snags on lens -> build up of aqueous beneath it -> pushes iris further forward and blocks trabecular meshwork. So mid-dilation of pupil can provoke attack (stress, excitement, watching TV in dim light, anticholinergics, topical mydriatics)
Closed-angle glaucoma signs
- Signs of Closed – unwell.
- Red eye (ciliary flush – redness more marked around periphery of cornea).
- Hazy cornea /pl. mglisty/
- Non-reactive (or minimally reactive)
- mid-dilated pupil
- Palpation - globe hard.
- Acute attack usually unilateral but long term Mx is both eyes. Emergency!
Open- angle glaucoma -> signs and symptoms
- Usually asymptomatic (until late stage)
- Signs of Open: Tonometry – measures IOP
- optic discs – ratio of diameters of cup (pale centre) to whole disc. normal cup:disc = 0.3 ( but up to 0.7 can be normal).increase in cupping over time suggests glaucoma.
Treatment of closed angle glaucoma
- Closed angle glaucoma -> Refer immediately
- topical glaucoma Rx: IV acetazolamide -> to reduce secretions and pilocarpine (cholinergic) -> to induce pupillary constriction
- Lay supine
- Then – surgery or laser to re-establish drainage
Treatment of open-angle glaucoma (general, classes no names)
Open - angle glaucoma Rx:
- reduce IOP
- Topical Beta Blockers (1st) – decrease aqueous production in eye
- OR topical prostaglandin analogue (2nd) (increase outflow)
- Then sympathomimetic or carbonic anhydrase inhibitor (topical or oral acetazolamide) –> decrease aqueous production
What’s are the risks associated with cochlear implants?
Cochlear implants – option for severe (or worse) deafness if normal aid not helped.
- Very small increased risk bacterial meningitis - hence need pneumococcal vaccine (all children should now get routinely anyway)
What are ‘bone anchored’ hearing aids used for?
Bone Anchored Hearing Aids – for conductive / mixed loss
- titanium implant just behind ear, uses direct bone conduction
What’s the principle of autoinflation? What is it used for?
Autoinflation
- child learning to blow up a balloon through their nostril rather than their mouth -> to hold open their eustachian tube -> pressure in their middle ear to equalise with atmospheric pressure
- can prescribe or buy OTC special devices (e.g. Otovents, about £7 from pharmacies or £4.90 to the NHS) that consist of a plastic nozzle and a couple of balloons. Can’t use normal balloons as they are too hard to blow up
- Use it three times daily (ideally). One balloon lasts 3-4 days so a pack lasts 2 weeks.
What’s Meniere’s disease?
- cause
- some symptoms
Meniere’s disease
Meniere’s disease is a disorder of the inner ear of unknown cause. It is characterised by excessive pressure and progressive dilation of the endolymphatic system.
- vertigo, tinnitus and hearing loss
- Symptoms resolve between attacks -> but a degree of hearing loss may occur
- Acute attacks last 5–15mins, then burn out leaving disequilibrium, tinnitus and moderate hearing loss
Diagnosis of Meniere’s disease - what Ix and finding confirm it?
What further Ix are needed and why?
- History and an audiogram showing low frequency hearing loss will make the diagnosis
- Referral is recommended for MRI to rule out acoustic neuroma
- DVLA must be informed if attacks are sudden and disabling
What are the drugs that cause ototoxicity?
Drugs: aminoglycosides, cis-platinum, salicylates, quinine, some loop diuretics, macrolides
- May have long term hearing impairment but if have associated balance disturbance that usually improves (central compensation)
What happens in Otosclerosis? (pathophysiology)
Otosclerosis
Otosclerosis describes the replacement of normal bone by vascular spongy bone.
- slowly progressing conductive hearing loss -> as stapes fixates on the oval window
- may extend into cochlea -> mixed conductive and SN hearing loss
Causes and risk factors of otosclerosis
- Inherited - autosomal dominant, but variable penetrance plus environmental factors
- measles can cause (incidence declining with vaccination)
Risk factors: white and Asian, women, age (teens to middle age), FH
Symptoms suggestive of otosclerosis
Sx of *otosclerosis*:
- progressive hearing loss and tinnitus
- usually low tone loss
- may have low volume speech due to enhanced bone conduction -> perceive own speech as loud
Ix for otosclerosis
Ix in *otosclerosis*:
- Audiogram - conductive hearing loss
Carhart’s notch = drop in bone conduction threshold of 20-30 dB esp at 2 kHz.
- Tympanogram may show ‘stiffness curve’
- CT
What prostaglandins analogues (name examples) are used for Rx of glaucoma?
Prostaglandin Analogues
- Latanoprost, bimatoprost, travoprost, tafluprost
- work by increasing the outflow of fluid from the eye
Side effects of prostaglandin analogues use in glaucoma Rx
Side effects include:
- possible changes in eye colour and eyelid skin
- stinging. itching, burning
- blurred vision
- eye redness
What is the name of beta-blocker used to Rx glaucoma?
Beta blockers such as timolol are the second most often used class of topical medication for glaucoma
MoA of B-blocker use in glaucoma
Topical beta-blockers -> reduce the intraocular pressure (IOP) by
- blockade of sympathetic nerve endings in the ciliary epithelium -> a fall in aqueous humour production.
Side effects of Timolol use
Timolol= beta-blocker used in glaucoma Rx
Side effects include:
- low blood pressure,
- reduced pulse rate
- fatigue, shortness of breath
*rarely: reduced libido, depression
* The systemic side effects of beta blockers can be minimized by closing the eyes following application or using a technique called punctal occlusion that prevents the drug from entering the tear drainage duct and systemic circulation.
What is the name of alpha-agonist that may be used in Rx of glaucoma?
- MoA
- side effects
- Alpha agonist = brimonidine
- MoA: work to both decrease production of fluid and increase drainage.
They act by decreasing aqueous humour secretion and increasing uveoscleral outflow
- Side effects: burning or stinging, fatigue, headache, drowsiness, dry mouth and nose, relatively higher likelihood of allergic reaction
Acetazolamide in glaucoma treatment
- class
- MoA
- side effects
Acetazolamide - carbonic anhydrase inhibitor
- Mechanism of action: for the reduction of Intraocular pressure
Acetazolamide inactivates carbonic anhydrase and interferes with the sodium pump, which decreases aqueous humour formation and thus lowers IOP .
- Side effects: stinging, burning, eye discomfort
Acetazolamide use in altitude sickness
Acetazolamide (or Diamox)
- prophylaxis agent for high altitude illness
- The medication is effective in preventing acute mountain sickness (AMS), high altitude pulmonary oedema (HAPE), and high altitude cerebral oedema (HACE).
MoA: inhibition of the carbonic anhydrase enzyme -> counteracts the respiratory alkalosis which occurs during ascent to altitude -> It facilitates the excretion of bicarbonate in the urine -> as a result, acetazolamide hastens acclimatization and helps prevent high altitude disorders
Features of Meniere’s disease
- recurrent episodes of vertigo, tinnitus and hearing loss (sensorineural). Vertigo is usually the prominent symptom
- a sensation of aural fullness or pressure is now recognised as being common
- other features include nystagmus and a positive Romberg test
- episodes last minutes to hours
- typically symptoms are unilateral but bilateral symptoms may develop after a number of years
Management of Meniere’s disease
- ENT assessment is required to confirm the diagnosis
- acute attacks: buccal or intramuscular prochlorperazine (dopamine antagonist/anti psychotic). Admission is sometimes required
- prevention: betahistine (H1 receptor agonist -> improves blood flow to the inner ear) and vestibular rehabilitation exercises may be of benefit
- patients should inform the DVLA. The current advice is to cease driving until satisfactory control of symptoms is achieved
