microbial keratitis

What are the types of Microbial keratitis (central cornea infections/inflammations)?

• bacterial

• Viral - herpes simplex and zoster

• Fungal

• Acanthameoba

• Interstitial

What are the other names for microbial keratitis?

• corneal infection

• Infectious keratitis

• Corneal ulceration

• Ulcerative keratitis

• Suppurative keratitis

What is the clinical definition of microbial keratitis?

Presumed infection of the cornea by replicating microbes, characterised by excavation of the corneal epithelium, Bowman’s layer and stroma infiltration and necrosis of the tissue which requires treatment with topical antibiotics..

• is sight threatening and requires immediate referral and tx

What are the symptoms of microbial keratitis?

1. Pain

2. Discharge - watering and/or micropurulent

3. Photophobia

4. Lid oedema

What are the clinical signs of microbial keratitis?

1. Severe generalised conjunctiva hyperaemia

2. Corneal oedema

3. Dense control and/or mid peripheral stromal infiltration

4. Epithelial and stromal erosion

5. Anterior chamber reaction/hypopyon

What are the signs/symptoms of bacterial keratitis?

1. Pain, photophobia, lacrimation

2. Mucopurulent discharge

3. Redness (ciliary flush)

4. Anterior chamber cells, possibly progress to keratic precipitates or hypopyon

What is pseudomonas keratitis?

Type of bacterial keratitis caused by a gram negative bacteria = pseudomonas aeruginosa

• very virulent and common especially in CL wearers

• Usually central and rapid

Is pseudomonas keratitis easy to treat?

Very difficult to treat and worse prognosis than other bacterial keratitis.

• also has potential necrotic liquefication of the cornea due to protease secretion leading to corneal weakening and perforation.

What is the treatment of bacterial keratitis?

• antibiotics, NO STEROIDS to begin with

• For pain = cycloplegia and oral analgesics.

• Hospital admission if px unable to comply to tx

Is corneal scraping a type of treatment for bacterial keratitis?

Yes, to see if corneal scape is sterile (usually ~50% of cases are).

• start antibiotics tx even when results from scrapes are known.

What is dosage of antibiotics for tx of bacterial keratitis?

Start on high doses of topical fluoroquinolones q1h (1 every hr) for 2 days.

• ciprofloaxin in warmer climates and of Lola in in cooler climates

If px has good response from this then q6h until completely resolved.

• steroids introduced after 2-3 days of progressive improvement to limit scarring.

What are the two types of viral keratitis?

1. Herpes simplex (HSV-1) - causes cold sore

2. Herpes zoster - causes genital infection

What is herpes simplex viral keratitis (HSV-1)?

Acute follicular conjunctivitis (initially, may cause just conjunctivitis or progress to viral keratitis)

• fine coarse keratitis in early stages but then progresses into a dendritic lesion (with terminal end bulbs)

What are the signs and symptoms of HSV-1?

1. Skin blister

2. Keratitis with mild watery discharge

3. Geographic ulcer

4. Reduced corneal sensitivity

What are the factors that cause HSV-1 to be recurrent?

1. Poor health

2. Sun

3. Fever

4. Mild trauma

5. Menstruation

6. Psychiatric problems/emotional stress

7. Use of topical or systemic steroids

Use prophylactic oral acyclovir to avoid recurrences.

What are the treatments for HSV-1?

• antiviral - 3% acyclovir ointment using 1cm ribbon to apply onto inferior fornix. 5x a day for 14 days or 3 days after healing.

• Cycloplegic for pain management

• If stromal and endothelium involvement = rapid referrral

What is herpes zoster ophthalmicus (viral keratitis)?

(Herpes zoster causes shingles and chickenpox that occurs anywhere on the body)

Virus in the trigeminal ganglion involving branches of the ophthalmic division.

• unilateral and usually in middle aged to elderly people.

What are the signs of herpes zoster ophthalmicus?

1. Painful, erythematous and blistered forehead

2. Hutchinson’s sign when lesion spreads to tip of nose

3. Cornea - subepithelial opacities, dendriform-like lesions (sharp edges) and deeper stromal infiltrates

4. Iridocyclitis

5. Reduced corneal sensitivity

6. Lid oedema

What is the treatment for herpes zoster ophthalmicus?

Early oral acyclovir 800mg 5x a day for 5 days within 72hrs of start of rash (for pain and morbidity0

• otherwise valacyclovir or famcyclovir

• Atropine and steroids if uveitis or stromal keratitis present

• If corneal very anaesthetic = tarsorrhaphy

Condition is contagious during vesicular stage - should avoid ppl who haven’t had chicken pox and pregnant women)

What can herpes infections involve?

It can involve the posterior segment.

Rare but possibie to cause acute retinal necrosis, is devastating

• Hence must dilate if px has any viral infection

• Same day referral if retinal lesions or vitreous haze is present

What is fungal keratitis?

Rare

Commonly caused by:

• contact with vegetable matter (filamentous)

• History of ocular disease or prolonged use of topical steroids (candida)

What are the signs/symptoms of fungal keratitis?

• grey-white indistinct lesions with feathery projections

• Multiple satellite foci

What is the treatment for fungal keratitis?

fungal keratitis is destructive and difficult to treat

• must refer, usually to hospital

• Topical natamycin 5% (first agent of choice)

What is acanthameoba keratitis?

Caused by freshwater amoeba

• seen in brackish water, wearing CLs while swimming, poor CL hygiene (tap water)

• Also ppl in pool/spa water with a corneal abrasion

What are the signs/symptoms of acanthameoba keratitis?

1. Pain

2. Keratitis

3. Early signs are subtle but will see irregular greyish epithelial keratitis, focal stromal infiltrates, peri neural infiltrates

4. Ring infiltrate

What is the treatment for acanthameoba keratitis?

• diagnosis is difficult but important so if suspicious must refer.

• topical neosporin

• Cycloplegic for pain management

• Tx can continue for months

What is interstitial keratitis?

Rare

• Most commonly caused by congenital syphilis

• Also caused by herpes and mycobacteria (TB)

What are the signs/symptoms of interstitial keratitis?

1. Redness, photophobia, pain and lacrimation (acute phase)

2. Active inflammation within the corneal stroma

• stromal vascularisation and oedema

• Anterior chamber cells and keratic precipitate

3. Deep stromal scarring and ghost vessels

What is the treatment for interstitial keratitis?

• topical steroids

• Cycloplegic for pain management

• Address underlying cause