Microbial Keratitis and Peripheral Corneal Changes/Ulcerations

Microbial Keratitis and Peripheral Corneal Changes/Ulcerations

Peripheral Corneal Changes/Ulcerations

  • Dellen

  • Marginal keratitis

  • Rosacea

  • Phlyctenular disease

  • Terrien’s marginal degeneration

Microbial Keratitis

  • Bacterial

  • Viral

  • Fungal

  • Acanthamoeba

  • Interstitial

Microbial Keratitis – Terminology

  • Also called:

    • Corneal infection

    • Infectious keratitis

    • Corneal ulceration

    • Ulcerative keratitis

    • Suppurative keratitis

Microbial Keratitis

  • Clinical Definition:

    • Presumed infection of the cornea by replicating microbes.

    • Characterized by excavation of the corneal epithelium, Bowman’s layer, and stroma with infiltration and necrosis of the tissue.

    • Requires treatment with topical antibiotics.

    • Sight threatening; requires immediate referral.

Symptoms

  • Pain

  • Discharge: watering and/or mucopurulent

  • Photophobia

  • Lid oedema

Signs

  • Severe generalised conjunctival hyperemia

  • Corneal oedema

  • Dense central and/or mid-peripheral stromal infiltration

  • Epithelial & stromal erosion

  • Anterior chamber reaction/ hypopyon

  • ciliary flush (not in conjunctivitis)

MK Incidence

  • Rare: Annual incidence of MK:

    • 0.63 per 10,000 (Hong Kong, Lam et al, 2002)

    • 0.36 per 10,000 (Scotland, Seal et al, 1999)

  • reason for low incidence → cornea has tight junction in epithelium and prevent pathogens entering, tears have antimicrobial and antibacterial material. → these work together to defend eye against infection.

Causes

  • Review of 291 patients (casualty and in-patient) over 2 years at RVEEH, Melbourne (Keay, Edwards et al, 2006):

    • Trauma: 37%

    • Contact lens: 34%

    • Unknown: 8%

    • Ocular Surface Disease (OSD): 6%

    • Systemic: 2%

    • Herpetic: 7%

    • Multifactorial: 6%

  • do not need to remember percentages.

MK - Causative Organisms

  • Table 2. Organisms Isolated in Microbial Keratitis Cases (Excluding Presumed Herpetic Keratitis, n = 246)

    • Gram-positive bacteria

      • Staphylococcus aureus

      • Coagulase-negative Staphylococcus

      • Streptococcus pneumoniae

      • Other Streptococcus species

      • Corynebacterium species

      • Propionibacterium species

    • Gram-negative bacteria

      • Mixed gram-negative rods

      • Pseudomonas aeruginosa

      • Serratia species

      • Haemophilus influenzae

      • Other enteric species

      • Other nonenteric species

    • Amoeba

      • acanthamoeba

    • Fungal

      • Filamentous fungi

      • Candida albicans

    • Sterile samples

  • ocular surface → gram positive

  • ocular trauma → fungal disease

Microbial Keratitis - Causes

  • Bacterial

  • Viral

    • Herpes simplex

    • Herpes zoster

  • Fungal

  • Acanthamoeba

  • Interstitial

Bacterial Keratitis

Signs/Symptoms

  • Pain, photophobia, lacrimation

  • Mucopurulent discharge

  • Redness (ciliary flush)

  • AC cells, possibly KP or hypopyon

Pseudomonas keratitis

  • Pseudomonas aeruginosa

  • Virulent and common (esp CL)

  • Usually central and rapid

  • More difficult to treat and worse prognosis than other bacterial keratitis

  • Potential necrotic liquefication of the cornea (rapid K weakening and perforation) due to protease secretion.

    • “melting of cornea”

Bacterial Keratitis - Treatment

  • Antibiotics

  • NO STEROIDS (to begin with)

  • Cycloplegic if required (and oral analgesia)

  • Hospital admission if unable to comply with Tx

  • Corneal scraping - start antibiotics before results return (~50% scraps will come back sterile)

  • Loading dose:

    • Topical fluoroquinolones (ciprofloxacin or ofloxacin) Q1h for 2 days

      • ciprofloxacin = hot climates

      • ofloxacin = cool climates

    • If good response, QID until completely resolved

  • Steroid after 2-3 days of progressive improvement (FML acetate) to limit scarring

Viral Keratitis

Herpes Simplex (HSV-1)

  • Acute follicular conjunctivitis

  • Skin blister

  • mild watery discharge (compared to bacterial mucopurulent)

  • Fine coarse keratitis

  • Dendritic lesions (terminal end bulbs)

  • Geographic ulcer

  • Reduced corneal sensitivity

  • Recurrence

    • Poor health

    • Sun

    • Fever

    • Mild trauma

    • Menstruation

    • Psychiatric problems/emotional stress

    • Topical or systemic steroids

    • Prophylactic oral acyclovir

Treatment

  • Antiviral- 3% Acyclovir ointment

    • 1cm ribbon in inferior fornix

    • 5x day for 14 days or 3 days after healing

  • Cycloplegic for pain management

  • Rapid referral for stromal and endothelial involvement

Herpes Zoster Ophthalmicus

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

  • Unilateral, usually in middle aged to elderly people

  • Signs:

    • Painful, erythematous and blistered forehead

    • If lesions to tip of nose, eye complications likely (Hutchinson’s sign)

    • Cornea:

      • Subepithelial opacities

      • Dendriform-like lesions (sharp edges) and deeper stromal infiltrates

    • Iridocyclitis

    • Corneal anaesthesia

    • Lid oedema

Hutchinson's sign

Cranial Nerve 5 (CNV)

  • CNV1: Ophthalmic Nerve (V1)

  • CNV2: Maxillary Nerve (V2)

  • CNV3: Mandibular Nerve (V3)

Treatment:

  • EARLY oral Acyclovir 800mg 5 times a day for 5 days (within 72 hrs of start of rash)

  • OR: Valacyclovir (1g PO q8h for 7 days) OR famcyclovir (250mg PO q8h for 7 days)

  • Atropine and steroids for uvea

  • Tarsorrhaphy if cornea is very anaesthetic

  • Contagious during the vesicular stage (patient should avoid people who haven't had chicken pox and pregnant women)

Herpetic Infections - Posterior Segment

  • May also involve the posterior segment.

  • Acute retinal necrosis is rare but devastating.

  • DILATE!

  • If retinal lesions or vitreous haze are noted, same-day referral is essential.

Fungal Keratitis

  • Rare

  • Commonly caused by:

    • Contact with vegetable matter (Filamentous)

    • Hx of ocular surface disease or prolonged use of topical steroids (Candida)

  • Signs/Symptoms:

    • Grey-white indistinct lesions with feathery projections

    • Multiple satellite foci

  • Treatment

    • Destructive and difficult to treat (high Tx failure rate)

    • Refer

    • Hospital

    • Topical Natamycin 5% first agent of choice

Acanthamoeba Keratitis

  • Freshwater amoeba

  • Brackish water, wearing contact lenses while swimming, poor CL hygiene (tap water), exposure to pool/spa water with corneal abrasion

  • Signs/Symptoms:

    • PAIN!!!

    • Keratitis - but degree of pain exceeds the signs

    • Early signs can be subtle (irregular greyish epithelial keratitis, focal stromal infiltrates, perineural infiltrates - adjacent to or along a nerve)

    • Ring infiltrate

  • Treatment:

    • Refer IMMEDIATELY

    • Diagnosis difficult, but important.

      • confocal microscopy image.

    • Topical neosporin, chlorhexidine, polyhexamethylene (PHMB), propamidine (Brolene)

    • Cycloplegic

    • Treatment can continue for months (very resistent to treatment)

Interstitial Keratitis

  • Rare

  • Caused by: congenital syphilis (most common), herpes, mycobacteria (TB)

  • Signs/Symptoms:

    • Redness, photophobia, pain and lacrimation (acute phase)

    • Active inflammation within the corneal stroma

    • Stromal vascularisation and oedema

    • AC cells and KP

    • Deep stromal scarring and ghost vessels

  • Treatment:

    • Topical steroids - dappen immune response

    • Cycloplegia - pain management

    • Address the underlying cause