43. Inflammation of the cornea due to bacterial infections*

Microbial keratitis – bacterial & fungal.

• infectious keratitis: inflammation of the cornea
• caused by: bacteria, viruses, fungi or acanthus amoeba
• risk factors: plugged nasolacrimal duct, chronic inflammation of lacrimal sac, dry eyes, contact lenses, lagopthalmos (incomplete lid closure), neuroparalytic disturbances, trauma
• local/systemic immunosuppressive drugs (inhibition of inflammatory processes but also of epithelization of the eye)
• symptoms: severe pain due to its sensitive innervation, redness, watery/purulent secretion, restricted visus, increased lacrimation, photophobia
• cause & complications depend on the virulence of the infecting agent as well as on the immune system
• complication: few h/days → corneal infiltration with ulcer formation & stromal fusion → corneal perforation → loss of the eye
• subsequent damage without treatment: scarring, clouding, perforation
• diagnosis: slit lamp examination, pap smear
• differential diagnosis: non-infectious keratitis
• treatment: depends on infecting agent

Bacterial Keratitis

• epidemiology: most common (90%) form
• etiology: staphylococci (S.aureus, S. epidermidis), streptococci (S. pneumoniae), Moraxella, Pseudomonas aeruginosa, Proteus mirabilis
• gonococci & diphtheria bacteria are able to infect intact epithelium
• increased risk with dacryostenosis (nasolacrimal duct), lacrimal duct infections, contact lenses (30% of cases)
• symptoms: progressive pain, foreign body sensation, purulent secretion, photophobia, mixed injection (combination of conjunctival & ciliar injection → elevated blood amount in blood vessels of the sclera & conjunctiva)
• types:

1. a) Keratitis punctate superficialis: multiple point-shaped lesions within corneal epithelium

• caused by: exogenous factors (bacteria, ciruses etc.), other keratitis forms, endogenous agents (Sicca-syndrome)
• symptoms: very variable → foreign body sensation, pain, decreased sensibility of the cornea
• fluorescence staining of lesions
• treatment: causal therapy & symptomatic substitution with artificial tears

1. b) ring ulcer: dissemination of the agent within the cornea

• etiology: Pseudomonas aeruginosa, posttraumatic or metastatic occurance
• symptoms: deep, limbus parallel corneal infiltrations/ulcerations, iritic irritations, conjunctival chemosis with mixed injection
• diagnosis: yellowish infiltration ring separated from the limbus by a clear zone, secondary surface defect, pap smear!
• treatment: immediate conjunctivial flap, broad spectrum antibiotics, pupil dilation by atropine, secondary glaucoma → acetazolamide, iris bombata → iridotomy, corneal perforation → keratoplasty á chaud

1. c) Ulcus cornea serpens: infiltration of the corneal stroma & fast dissemination into healthy cornea

• etiology: adults, after damage to the cornea & infection of the wound (Streptococci, Staphylococci, Pseudomonas aeruginosa)
• symptoms: mixed injection, pus accumulation within the anterior chamber = hypopyon, severe dull pain, increased lacrimation, photophobia, decreased visual acuity
• complications:
• without pupil dilation → adhesions between pupilar border & anterior lens capsule → involvement of the whole circumference → iris bombata with secondary glaucoma