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OD3 (S1&2) > DIS - Eye Trauma III: Chemical - Week 8 > Flashcards

DIS - Eye Trauma III: Chemical - Week 8 Flashcards

1
Q

Where do majority of chemical eye injuries occur?

A

At work

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2
Q

Do chemical injuries tend to be urgentocular emergencies or are they self-limiting?

A

Are urgent

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3
Q

What improves visual prognosis with chemical injuries?

A

Immediate irrigation

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4
Q

List 6 factors that affect the severity of a chemical ocular injury.

A

Nature of the chemical
Concentration
pH
Volume
Duration of exposure
How quickly treatment is initiated

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5
Q

What is the main group of chemicals that causes damage? List three others.

A

Alkali (80%)
Acids
Surfactants
Aerosols

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6
Q

List two common acids that can cause injury.

A

Sulphuric acid
Hydrochloric acid

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7
Q

List 4 common alkalis that can cause injury. List some common items these chemicals are found in.

A

Ammonia
-household leaning agents
-fertilisers
-refrigerants
Lye
-drain/oven cleaners
-airbags
Magnesium hydroxide
-firework sparklers
-flares
Lime
-plaster
-mortar
-cement
-whitewash

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8
Q

What are three common sources of chemicals that cause injury?

A

Household cleaning products
-especially bleach
Personal care products
-especially hair products
Car products
-especially battery acid

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9
Q

List four things that affect the severity of a burn with acids.

A

Concentration
Duration of exposure
pH
Protein affinity of acid anion

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10
Q

What happens when an acid reacts with the anterior cornea? Does it commonly reach the anterior chamber?

A

Binds with tissue protein and coagulates the corneal epithelium
Proteins precipitate in the anterior cornea
Forms a barrier to further penetration
Rarely reaches the anterior chamber

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11
Q

Do organic acids have strong or minimal penetration of the cornea? Do they often cause severe or mild symptoms?

A

Minimal
-mild symptoms

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12
Q

Which penetrates tissue quicker, alkali or acids?

A

Alkali

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13
Q

Above what pH are alkalis exceedingly dangerous?

A

> 11

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14
Q

What does the amount of damage from an alkali burn depend on?

A

Fat solubility

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15
Q

What common household product has a strong ability to dissolve fat?

A

Ammonium hydroxide

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16
Q

What effect do alkalis have on collagen?

A

Destroys them

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17
Q

What is often seen with alkali burns of the eye?

A

Initial appearance can be decieving
May be worse with time

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18
Q

Can alkalis penetrate into the anterior chamber?

A

Yes

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19
Q

What is the major ingredient in cement and lime that can result in alkali burns? Does this account for many or few causes of chemical injury? Are they serious?

A

Calcium oxide in the major ingredient
Lime burns are very serious and one of the most common causes

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20
Q

List the three main groups of detergents. Note the charge for each.

A

Cationic - positive
Anionic - negative
Non-ionic - neutral

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21
Q

What effect do cationic detergents generally have on the eye? What about when severe?

A

Precipitates proteins of the cornea and conjunctiva
If severe, corneal opacification and vascularisation

22
Q

What effect do anionic detergents generally have on the eye?

A

Heals quickly with no permanent damage

23
Q

What effect do non-ionic detergents generally have on the eye?

A

Can produce corneal erosion, but heals without scarring

24
Q

What effect do surfactants and solvents generally have on the eye (4)?

A

Persistent corneal epithelial defects
Stromal oedema
Endothelial cell loss
Subepithelial plaques

25
Q

List 8 signs and symptoms of chemical injury due to aerosols.

A

Hyperaemia
Swelling
Blepharospasm
Lacrimation
Pain
SPK
Cornea/conj sloughing off
Corneal oedema

26
Q

What is the principle ingredient of capsicum sprays? What are the signs/symptoms (5)?

A

Oleoresin capsicum
Signs and symptoms as in aerosols with the addition of:
Total epithelial defect
Conjunctival chemosis and necrosis
Stromal oedema
Symblepharon

27
Q

List 8 general signs and symptoms of chemical ocular injury.

A

Hyperaemia
Haemorrhage
-conjunctival
-periorbital
Lacrimation
Photophobia
Pain
-can cause damage to the extent of no pain
FB sensation
Reduced vision
Concurrent trauma

28
Q

What is the immediate management of a chemical injury?

A

Immediate and prolonged irrigation of the eye with sterile saline/water for 30 minutes or until neutral with litmus paper

29
Q

How long can alkali injuries take to turn neutral?

A

Up to 2 hours

30
Q

What part of the eye should be used to assess pH?

A

Tears

31
Q

Should eyes with chemical injury be padded?

A

no

32
Q

Once immediate care is given, how should severe chemical injury be managed?

A

Refer grades 3 and 4 for ophthalmological care

33
Q

Consider less severe grades of chemical injury. How should they be worked up and managed once immediate care has been given (5)?

A

After 30 mins of irrigation, use topical anaesthesia
Measure VA
Slit lamp exam
Evert upper lids
Remove particles/crystalline matter and necrotic tissue
-cotton bud soaked in anaesthetic
NaFl stain

34
Q

What two things should you look for when working up a chemical injury?

A

Limbal ischaemia
AC reaction

35
Q

Describe grade 1 chemical injury (2). Note the prognosis.

A

Clear cornea
No limbal ischaemia
Excellent prognosis

36
Q

Describe grade 2 chemical injury (2). Note the prognosis.

A

Cornea hazy, but iris details visible
Limbal ischaemia >1/3
Good prognosis

37
Q

Describe grade 3 chemical injury (2). Note the prognosis.

A

No iris details
Limbal ischaemia 1/3 to 1/2
Guarded prognosis

38
Q

Describe grade 4 chemical injury (2). Note the prognosis.

A

Opaque cornea
Limbal ischaemia >1/2
Very poor prognosis

39
Q

What are injuries of grade 1 chemical injury confined to?

A

Corneal epithelium

40
Q

What may occur when grade 2 chemical injury resolves (3)?

A

Cornea may develop focal haze and neovascularisaion at the site of limbal stem cell loss

41
Q

What is the focus of management of chemical injury (2)?

A

Reepithelialisation
Reduction of inflammation

42
Q

Why is limbal ischaemia important in chemical injury? What clinical presentation regarding this should you be wary of?

A

Stem cells that renew the corneal epithelium are located exclusively in the limbal region
Loss or malfunction disrupts epithelial maintenance
Beware the very white eye

43
Q

List 10 treatment options for grade 1 and 2 chemical injury. Note dosages where appropriate.

A

Prophylaxis
-chlorsig/tetracycline qid
Cycloplegia
-for pain, qid
Analgaesia as appropriate
-ibuprofen
Artifical tears q1h
-to aid reepithelialisation
Topical steroids for more severe damage
-use for AC reaction q2h
Manage IOP
-timolol bid when needed
Adjunct therapy
-mostly for grade 3 to 4
Sodium citrate 4g po
Sodium ascorbate 500mg po
Tetracycline/acetylcysteine

44
Q

What is an acceptable IOP for chemical injury and what should be used when needed?

A

Accept ~30mmHg for 24h
-else use timolol 0.5% bid

45
Q

What grades are adjunct therapy typically used for?

A

Grade 3 or 4

46
Q

How does sodium citrate aid in chemical injury treatment (2)?

A

Inhibits infiltration and activation of PMNs reducing inflammation and degradation
Also inhibits corneal collagenases

47
Q

How does sodium ascorbate aid in chemical injury treatment (2)?

A

Promotes collagen synthesis
-reduces loss of stroma

48
Q

How does tetracycline/acetylcysteine aid in chemical injury treatment (2)?

A

Inhibits MMP by binding to Zn2+ in collagenase
Prevents stromal degradation

49
Q

What should the follow-up of chemical injury be?

A

Daily until epithelium is healed

50
Q

What are five later referrals that could be made for chemical injury?

A

Division of scarring adhesions of the conjunctiva
Conjunctival graft
Amniotic membrane graft to aid conjunctival and corneal reepithelialisation
Limbal stem cell graft to provide new corneal epithelium
Penetrating keratoplasty

51
Q

Does an amniotic membrane graft replace stem cells?

A

No

OD3 (S1&2) (114 decks)

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