Infective Keratitis

Question 1

What is keratitis?

Answer 1

Sight-threatening infection and inflammation of the cornea.

Question 2

Give some bacterial causes of keratitis

Answer 2

1) Staph. aureus (most common)

2) Pseudomonas aeruginosa

Question 3

What is the most common bacterial causes of keratitis?

Answer 3

Staph. aureus

Question 4

What bacteria causes keratitis in contact lens wearers?

Answer 4

Pseudomonas aeruginosa

Question 5

What are some viral causes of keratitis? (2)

Answer 5

1) HSV

2) VZV

Question 6

What are some fungal causes of keratitis? (3)

Answer 6

1) Aspergillus

2) Candida

3) Fusarium

Question 7

What is a protozoan cause of keratitis?

Answer 7

acanthamoebic keratitis

Question 8

What increases risk of acanthamoebic keratitis?

Answer 8

Eye exposure to soil or contaminated water

Question 9

Risk factors for bacterial keratitis?

Answer 9

Those which disrupt the healthy corneal epithelium:

1) Contact lens wear

2) Corneal trauma e.g. previous ocular surgery, foreign body, chemical injury

3) Ocular surface disease e.g. dry eye, lid malposition, chronic blepharitis

4) Immunosuppression e.g. drugs, immunodeficiency syndromes, diabetes

Question 10

What is the most common risk factor for bacterial keratitis?

Answer 10

Contact lens wear, especially in prolonged use and poor lens hygiene

Question 11

Are features of bacterial keratitis usually unilateral or bilateral?

Answer 11

Unilateral

Question 12

Symptoms of bacterial keratitis?

Answer 12

1) Ocular pain e.g. irritation and foreign body sensation

2) Red eye

3) Reduced visual acuity

4) Photophobia

5) Purulent discharge

Question 13

A history of contact lens wear is essential in bacterial keratitis. What questions should you ask?

Answer 13

1) Type of contact lenses used: daily disposable, monthly or extended-wear

2) Duration of wear per day

3) If they have ever slept, showered, or swam with their lenses in

Question 14

A hypopyon may be seen in bacterial keratitis. What is this?

Answer 14

The accumulation of WBCs that form a whitish layer of fluid in the lower portion of the eye’s anterior chamber.

Question 15

Relevant investigations in bactieral keratitis?

Answer 15

Bacterial keratitis is a clinical diagnosis.

Can do corneal scrapes and conjunctival swabs in severe or treatment-resistant cases.

Question 16

Mx of bacterial keratitis?

Answer 16

1) Discontinue contact use immediately

2) Topical abx (typically quinolones are used first-line)

3) Oral abx in severe cases

Question 17

Complicatins of bacterial keratitis?

Answer 17

1) Spread of infection - can lead to endophthalmitis

2) Corneal perforation (severe cases)

3) Residual dense corneal scarring

4) Irregular astigmatism

5) Formation of cataract: secondary lens opacification is common following severe inflammation

Question 18

Is herpes simplex keratitis more commonly caused by HSV-1 or HSV-2?

Answer 18

HSV-1

Question 19

How can HSV-1 cause keratitis?

Answer 19

Primary infection with HSV-1 is usually acquired in childhood.

Following the resolution of the primary infection, HSV travels through the sensory nerve to the trigeminal ganglion, establishing latency.

Subsequent reactivation can result in epithelial keratitis.

Question 20

Clinical features of herpes simplex keratitis?

Answer 20

• red, painful eye
• photophobia
• epiphora (watering of the eye) as opposed to purulent discharge seen in bacterial
• decreased visual acuity

Question 21

What is a pathognomonic sign for herpex simplex keratitis?

Answer 21

Dendritic ulcer with linear branching morphology and terminal bulbs.

The bed of the ulcer will stain green with fluorescein, while the ulcer margin will stain with rose Bengal.

Question 22

Investigations in HSV simplex keratitis?

Answer 22

HSV keratitis can be diagnosed clinically with the identification of a dendritic ulcer.

Question 23

Mx of herpes simplex keratitis?

Answer 23

1) Discontinue contact lens use immediately

2) Topical antivirals e.g. aciclovir 3% ointment

3) Epithelial debridement

Question 24

What is herpes zoster ophthalmicus?

Answer 24

Reactivation of VZV (shingles) affecting the ophthalmic branch of the trigeminal nerve (V1).

Question 25

What investigation is required to diagnose keratitis?

Answer 25

Slit lamp exam

Question 26

What will flluorescein staining show in herpes simplex keratitis?

Answer 26

dendritic corneal ulcer

Question 27

What is an option to treat permanent scarring and vision loss after keratitis?

Answer 27

Corneal transplant