Cornea (pt 2, Infectious/Microbial Conditions)

Questions to think about when a patient comes in with a corneal problem

• Layer of the cornea involved?

• Pain?

• Staining?

• Central or peripheral?

• Red or white eye?

Potential Dx for a corneal complaint with red eyes

Infections, inflammation, trauma

Potential Dx for a corneal complaint with white eyes

Dystrophies, degenerations, thinning, pigmentation

Infectious keratitis classifications

• Microbial (bacterial, fungal, or parasite)

• Viral

Infectious keratitis etiology

• Bacterial: Staph, pseudomonas

• Fungal: Fusarium, candida

• Parasite: Acanthameoba

• Viral: Herpes simplex/zoster

Bacterial keratitis

Most common type of microbial keratitis

Bacterial keratitis risk factors

• Non-compliant CL wearers

• Topical steroid (decrease immune response → increase risk for infection)

• OSD

• Trauma (esp with something dirty)

• Previous infection

Bacterial keratitis clinical findings

• Deep corneal infiltrate

• Epithelial defect over a central infiltrate (usually same size)

• Diffuse conj hyperemia

• Ant chamb rxn

Infectious corneal ulcer will…

Have an epithelial defect the same size as the infiltrate

Bacterial keratitis lab testing

Culture and smears

Will take time for results → Start Tx and then change depending on results

Bacterial keratitis complications

• Scarring

• Irregular astigmatism (may need specialty lens)

• Neovascularization

• Perforation

If there is corneal stroma involved…

A scar will form

Bacterial keratitis Tx

• Topical antibiotic (broad spectrum) solution or ointment

  • Need round clock Tx

• Topical cycloplegics

• Topical steroids (after 2-3 improvement with antibiotic with re-epithelialization)

• Oral antibiotics (gonococcal only)

Step wise treatment

Why would you use topical cycloplegics

Iris is inflamed because of ant chamb rxn

Secondary uveitis

Clinical pearls for bacterial keratitis Tx

• Broad spectrum antibiotic until cultures are returned

• Can include mono or duotherapy (2 drug classes)

Fungal keratitis

Caused by 2 types of fungi

Yeast: Candida (temperate climates)

Filamentous: Fusarium or aspergillus (tropical climates)

Fungal keratitis risk factors

• OSD

• Long term steroid use

• Trauma with vegetative matter

• CL wearers

• Immunocompromised

Shared characteristics between fungal keratitis types

• Conj hyperemia

• Endothelial plaques (inflammatory and immune cells)

• Ant chamb rxn and hypopyon

Yeast fungal infection keratitis

Round button infiltrate, no feathery borders or satellite lesions, liquified stroma

Ulcers in infectious corneal kertitis are…

Central

Filamentous fungal infection keratitis

Feathery ulcer borders, satellite lesions

Fungal infection keratitis complications

• Scarring

• Perforation

• Endophthalmitis

Fungal infection keratitis Tx

• Debridement (take off more epithelium for better drop penetration)

• Topical antifungal

• Topical antibiotic drop (prevent secondary infection

Identify and refer out

Confocal microscope

Provides cellular level images of the corneal layers

Used to diagnose corneal pathology such as bacterial, fungal, or acanthamoeba

Can fungal keratitis be cultured?

No

Acanthamoeba keratitis

Protozoa in soil and water

Trophozoite and Cyst stages

Trophozoite acanthamoeba stage

Active stage

Feeds and reproduces

Cyst acanthamoeba stage

Dormant stage

Resistant to harsh conditions, temp changes, and standard disinfections

Acanthamoeba keratitis risk factors

• CL with water exposure

• OSD

• Trauma

• Topical steroid

Acanthamoeba keratitis clinical findings

• Pain that does doesn’t match slip lamp findings

• Ant chamb rxn

• Conj hyperemia

Early: PEE, diffuse microcystic epithelial changes, pseudodendrites (often misdiagnosed as Herpes simplex)

Intermediate: Radial perineuritis, multifocal stromal infiltrates

Late: Ring infiltrate

Radial perineuritis

Occurs in intermediate stage acanthamoeba keratitis

Inflamed corneal nerves

Acanthamoeba keratitis complications

• Scleritis

• Hypopyon

• Corneal scarring or melting

• Secondary glaucoma

• Retinal inflammation

Acanthamoeba keratitis Tx

• Topical antimicrobials

Pool cleaners

Penetrating keratoplasty (PK)

Corneal surgery where all layers of cornea are replaced

Used for corneal opacifications and diseases that affect all layers

Bacterial keratitis hallmark signs

Deep corneal infiltrate with same size overlaying epithelial defect

Fungal keratitis hallmark signs

Filamentous: Deep corneal infiltrate with feathery borders and satellite lesions

Yeast: Deep corneal infiltrate that’s round

Acanthamoeba keratitis hallmark signs

Multiple stages:

• Epithelial defects or haze with pseudodendrite

• Radial perineuritis and stromal infiltrates

• Ring infiltrate