BACTERIAL KERATITIS

Dr Md Ferdous Islam

Introduction• Bacterial keratitis usually develops when ocular defens have been compromised.

•Host cellular and immunologic responses to offending agent which may be bacterial, viral, fungal or protozoal organisms leads to formation of ulcer.

•Sight threatening condition and should be considered as ocular emergency.

Barriers Of Microbial Infection

• Bony orbital rim,eyelids,• Intact corneal & conjunctival epithelium

Anatomical

• Tear film-mucus layer• Lacrimal system

Mechanical

• Tear film constitutes-IgA, complement components, and enzymes lysozyme, lactoferrin, betalysins

• CALT

Antimicrobial

Risk Factors • 1. TRAUMA -breach in corneal epithelium -refractive surgery -agricultural injury -inoculation of organism• 2. OCULAR SURFACE DISEASES - blepharitis, ectropion, entropion, trichiasis, lagophthalmos, chronic dacryocystitis• 3.CONTACT LENS WEAR• 4. LOCAL IMMUNE SUPPRESSION DUE TO TOPICAL CORTICOSTEROIDS

Systemic Factors

1.Malnutrition2.Diabetes3.Immunosupression-Systemic steroids, AIDS4.Chronic alcoholism

Aetiology • Caused by organisms which produce toxins causing tissue death i.e.

necrosis characterized by pus formation. • Such purulent keratitis is usually exogenous due to infection by

pyogenic bacteria such as -Pseudomonas, -Staphylococcus, -Streptococcus, -N. gonorrhoeae and -C. diphtheriae

Aetiology

• Most of the bacteria are capable of producing corneal ulcer only when the epithelium is damaged.

• N. gonorrhoeae, C. diphtheriae, Haemophilus , N. meningitidis

can penetrate intact corneal epithelium.

Pathogenesis Corneal abrasion Microbes adhere to epithelium, cloning ,invasion to stromal

lamellae,release toxins & lytic enzymes Host response PMNs at the site of ulcer from tears & limbal vessels release of cytokines &

interleukins progressive invasion of cornea & increase in size of ulcer

Phagocytosis

Release of free radicals, proteolytic enymes Necrosis & sloughing of epithelium, Bowman’s membrane & stroma

A saucer shaped defect with projecting walls above the normal surface due to swelling of tissue resulting from fluid imbibition by corneal stroma with grey zone of infiltration

Presentation

1. Diminution of vision, depending on location of corneal ulcer 2. Watering due to reflex lacrimation3. Photophobia 4. Pain due to exposed nerve endings5. Mucopurulent / purulent discharge

Ocular Examination

1.Visual acuity-reduced2.Slit lamp Biomicroscope Lids - edema Conjunctiva – Ciliary congestion

4. Cornea -Location of the ulcer- central, paracentral peripheral,total.

-Size , shape, depth, margins & floor- depends on stage of ulcer. -Density and extent of stromal infiltration.

5. Anterior chamber - Cells/flare, mobile Hypopyon.

Iris- muddy Toxin induced iritisPupil – miotic

Other:-Sac syringing -corneal sensation-Fluorescein staining

Special Features1.Staphylococcal • Central,oval, opaque• Distinct margins.• Mild oedema of remaining

cornea.• Stromal abscess in

longstanding cases.• Mild to moderate AC reaction.• Affects compromised corneas

e.g. Bullous keratopathy , dry eyes , atopic diseases.

2.Pneumococcal• Ulcer serpens is greyish white

or yellowish disc shaped ulcer occuring near center of cornea.

• starts at periphery & spreads towards centre

• Tendency to creep over the cornea in serpiginous fashion- Ulcus Serpen.

• Violent iridocyclitis is often associated with it.

• Hypopyon – always present• It has great tendency for

PERFORATION.

3. Pseudomonas

• Rapidly spreading.• Extends periphery & deep

within 24 hrs.• Stromal necrosis with shaggy

surface• Spreads concentrically and

symmetrically to involve whole depth of cornea-Ring ulcer.

• Greenish-yellow discharge.• Hypopyon is present.• Untreated corneal melting.

4. Streptococcus viridans

• Infectious crystalline keratopathytype of stromal keratitis.

• Crystalline arborifoem (needle like) white opacities in stroma , not associated with infiltration & ocular inflammation

• Due to proliferation of bacteria between the stromal lamellae.

Complications Of Corneal Ulcer 1. Spread of ulcer horizontally and depth-wise, leading to thinning

of cornea2. Descemetocele 3. Perforation of ulcer – sudden exertion such as coughing, sneezing, straining at stool or

firm closure of eyes increase in intra-ocular pressure (IOP) perforation

a) Peripheral perforation -iris prolapse through opening. Exudation takes place on prolapsed tissue an adherent leucoma .

b) Central perforation anterior chamber collapse lens comes in contact with corneal endothelial surface anterior capsular cataract repeated healing and perforation leading to corneal fistula formation

c) Sloughing of whole cornea: prolapse of iris pupillary block and exudation on iris pseudocornea anterior synechiae angle of anterior chamber is occluded leading to secondary glaucoma anterior staphyloma .

d) Intra-ocular purulent infection: due to perforation bacteria enter in the eye and causes endophthalmitis / panophthalmitis

Investigations

Specific – Corneal scraping Gram stain, Culture & Antibiotic sensitivity Culture of contact lens & solution Conjunctival Swab

Treatment

Gen Consideration

• Hospitalization• Discontinuation of contact lens wear• Eye shield

LOCAL TREATMENT

Control of infection with appropriate antibiotic(s)a. based on clinical judgment b. based on finding of smear examinationc. based on culture and sensitivity report

• Antibiotic Monotherapy -fluroquinolone -Ciprofloxacin or Ofloxacin -New generation fluroquinolone

• Antibiotic duotherapy

•Subconjunctival antibiotics•Mydriatics•Steroids

Systemic Antibiotics

Indications • Severe keratitis• Scleral involvement• Hypopyon• Impending perforation• Frank perforation with risk of intraocular spread• Infection in children• P. aeruginosa infection• N. meningitidis infection• H. influenzae • N. gonorrhoeae infection

Adjuvant Therapy1.Cycloplegic : Atropine 1% or cyclopentolate 1% or

Homatropine 2%- prevents ciliary spasm, relieves pain, breaks adhesions and prevent synechia formation.

2.Analgesic anti-inflammatory3. Oral vitamin C4. Acetazolamide Tab - impending perforation or perforated

corneal ulcer and in cases where there is raised IOP

Treatment Of Impending Perforation1. Straining should be avoided.2. Pressure bandage3. Lowering of IOP4. Tissue adhesive glue (cynoacrylate)5. Conjunctival flap 6. Soft contact lens Bandage 7. Penetrating keratoplasty

Treatment Of Perforated Corneal Ulcer

• Tissue adhesives• Conjunctival flap• Soft bandage• Keratoplasty

• Modification of initial antimicrobial therapy:-Should be based on clinical response not on culture sensitivity

• If pt is responding no change in initial treatment• If pt is not responding/ worsening drugs are changed

according to antimicrobial sensitivity

• SIGNS OF HEALING : -resolution of lid edema, congestion -decreased density of stromal infiltrate -reduction of corneal oedema -reduction in AC reaction/hypopyon -re-epithelization -corneal vascularization

• Antibiotic frequency-tapered to 4hrly after 72 hrs

• SIGNS OF NON-RESPONSE- Increase in infiltration, epithelial defect, height of hypopyon,

Corneal thinning, perforation

Treatment• Re-evaluate for

Drug toxicity,Non-infectious causes or Unusual organisms • Modification of anti-microbial therapy according to

antimicrobial sensitivity• Scraping of ulcer floor followed by cauterization with pure

(100%) carbolic acid or 10-20% trichloracetic acid.• Therapeutic keratoplasty

Topical Corticosteroids

• Controversial in bacterial keratitis• The rationale for using steroids - to decrease tissue destruction.

CRITERIA FOR TOPICAL STEROIDS IN ULCER --

1.Must not be used in presence of active infected corneal ulcer2.If bacteria shows in-vitro sensitivity to the antibiotic being used3.Patients compliance for follow-up4. No other virulent organism is found

Surgical Treatment• 1.Tissue adhesive-Cyanoacrylate glue- small perforations< 3mm - descemetocele• 2. Patch graft –perforation- 5mm in diameter• 3 . Therapeutic keratoplasty -large areas of perforation, necrosis -Non-healing ulcer

Thank you..