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Neurology and Special Senses > The Cornea, Lens and Intra-Ocular Pressure > Flashcards

The Cornea, Lens and Intra-Ocular Pressure Flashcards

1
Q

What is the cornea?

A

Avascular transparent structure that separate anterior chamber from tear film

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2
Q

What are the 3 main roles of the cornea?

A

Maintain transparency
Ocular protection
Refract light

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3
Q

Describe the epithelium of the cornea

A

5-7 cell layer thick non keratinized stratified squamous layer.

Cells migrate from basal layer to surface then sloughed off into tar film

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4
Q

How is corneal oedema seen?

A

Visible lines in the stroma

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5
Q

What happens to endothelial cell number with age?

A

Falls

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6
Q

What nerve supplies the cornea?

A

Opthalmic branch of the trigeminal nerve –> via long ciliary nerve

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7
Q

What can trigger an infection of the cornea?

A

Disruption of the epithelial surface caused by:

Trauma
Contact lens wear
Dry eyes
Pre-existing corneal disease
Systemic conditions - immunocompromised
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8
Q

What symptoms would a patient with infective keratitis present with?

A

Severe pain
Red eye
Epiphora - excess eye watering

possible reduced visual acuity
Photophobia
Mucus discharge

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9
Q

What would you expect to see on examination if you suspect infective keratitis?

A

White deposits in cornea - corneal infiltrate
Hypopyon - pus collect in anterior chamber

Anterior chamber may show cells and flare - leucocytes and protein respectively due to leaky blood vessels

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10
Q

What is the aqueous humour pathway?

A

Ciliary processes in ciliary body –> iris and anterior surface of lens –> pupil –> through iridocorneal angle –> trabecular meshwork –> Canal of Schlemm –> episcleral vessels –> systemic venous circulation

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11
Q

What is the unconventional drainage route for aqueous humour?

A

Uveaoscleral route - drain into root of iris and ciliary muscle –> scleral vascular system

10-20%

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12
Q

How is intraocular pressure measured?

A

Force needed to flatten corneal surface using tanometer - pressure at which green lines match

Must correct for corneal thickness

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13
Q

What is the normal intraocular pressure?

A

11-21mmHg

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14
Q

What does ocular hypertension put you at higher risk of?

A

Developing glaucoma

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15
Q

Which autonomic receptors control intra-ocular pressure?

A

Adrenergic - alpha 2 and beta 2

Cholinergic have little direct effect

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16
Q

What effect does alpha 2 have on intraocular pressure?

A

Reduce IOP by reducing aqueous production

May increase uveoscleral outflow

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17
Q

What effect does beta 2 have on intraocular pressure?

A

Increase IOP by increasing aqueous production

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18
Q

What drug classes are used to target intraocular pressure?

A 
Beta-blockers
Alpha antagonists
Prostaglandin analogues
Carbonic anhydrase inhibitors
Parasympathomimetics
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19
Q

Give examples of beta blockers and their MoA for intraocular pressure

A

Timolol, Carteolol

Reduce aqueous humour - block beta 2 receptors

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20
Q

Give examples of alpha agonists and their MoA for intraocular pressure

A

Apraclonidine, brimonidine

Reduce production of aqueous and slight increase in drainage

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21
Q

Give examples of prostaglandin analogues and their MoA for intraocular pressure

A

Latanoprost, Bimataprost

Increase uveoscleral outflow of aqueous humour

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22
Q

Give examples of carbonic anhydrase inhibitors and their MoA for intraocular pressure

A

Dorzolamid, Brinzolamide

Reduce production of aqueous humour by decreasing fluid transport in ciliary body

23
Q

Give examples of parasympathomimetics and their MoA for intraocular pressure

A

Pilocarpine

Increase outflow by ciliary muscle contraction causing trabecular meshwork to open

24
Q

What topical preparations are used in raised IOP?

A

Cosopt - timolol and dorzolamide

25
Q

What is the main function of the lens and how powerful is it?

A

Refraction

Refractive power less than cornea

26
Q

How does the lens change refractive power?

A

Changes shape (accommodation)

27
Q

How does the lens change shape?

A

Ciliary body contract –> pull suspensory ligaments –> flatten lens –> less refraction

vice versa if ciliary body relax

28
Q

What is presbyopia?

A

Lens’ ability to accomodate diminish with age

29
Q

What causes presbyopia?

A

Atrophy of ciliary muscle

Loss of lens elasticity

30
Q

How do inner lens fibres vary from outer lens fibres?

A

Inner fibres older and much harder then newer fibres on outside

31
Q

How does a lens maintain transparency?

A

Fibres are tightly packed and highly organised

32
Q

What is a cataract?

A

Loss of transparency of the lens

33
Q

What is the most common cause for cataracts?

A

Increasing age

34
Q

Why is early detection of cataracts crucial in newborns?

A

To salvage best vision possible

35
Q

What are common causes of cataracts in younger patients?

A

Trauma

Drugs - steroids, amiodarone, allopurinol

Systemic disease - Diabetes, myotonic dystrophy, neurofibromatosis type 2

36
Q

What are general symptoms of cataracts?

A

Painless loss of vision
Diplopia
Loss of red reflex
Difficulty with every day tasks

37
Q

What is the most common technique for cataract surgery?

A

Phacoemulsification

38
Q

What is the management for infectious keratitis?

A

Topical broad spectrum quinolone

39
Q

What is the prognosis for infectious keratitis?

A

Usually good

Risk of long term visual disability in:
Elderly, contact lens wearer, fungal disease

40
Q

What happens in a cataract lens?

A

Disruption of lens fibres leading to protein aggregation and deposition in the lens

Causes clouding, light scattering and vision obstruction

41
Q

What complications are associated with phacoemulsification?

A 
Rupture of posterior capsule
Infection
Inadequate correction for refractive error
Haemorrhage
Posterior capsule opacification
42
Q

What is a congenital cataract?

A

Inherited cataract

Cataract secondary to intrauterine infection - rubella

43
Q

What can happen in congenital cataracts aren’t removed?

A

Lead to nystagmus and amblyopia

44
Q

What are children who have surgery for a congenital cataract within their first year of life at risk of?

A

High risk of glaucoma

45
Q

What are the ADR’s associated with latanoprost?

A

Iris turn brown
Risk of uveitis and keratitis
Longer eyelashes

46
Q

What are the CI for latanoprost?

A

Uveitis

Pregnancy

47
Q

What are the ADR’s associated with Timolol?

A

Irritated, red, dry eye
Bronchospams
Bradycardia

48
Q

What are the CI’s for timolol?

A

Asthmatics

Heart block

49
Q

What are the ADR’s for Dorzolamide (carbonic anhydrase inhibitors)?

A

N&V
Headache
Dizzy

50
Q

What are the CI’s for carbonic anhydrase inhibitors?

A

Renal impairment

51
Q

What are the ADR’s associated with sympathomimetics (brimonidine)?

A

Dry eye

Postural hypotension

52
Q

What are the ADR’s associated with parasympathomimetics (pilocarpine)?

A

Blurred vision
Constricted pupil
Sweating
Bradycardia

53
Q

What the are CI’s associated with sympathomimetics?

A

Angle closure glaucoma

On MAOI’s

54
Q

What are the CI’s associated with parasympathomimetics?

A

Uveitis

Neurology and Special Senses (28 decks)

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