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BACTERIAL KERATITIS

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Title: BACTERIAL KERATITIS


1
BACTERIAL KERATITIS
  • Dr. Sanjay Shrivastava
  • Professor of Ophthalmology
  • Regional Institute of Ophthalmology
  • Gandhi Medical College
  • Bhopal (M.P.)
  • drs.rio_at_hotmail.com

2
Copy of Power point presentation of Lecture
taken for Junior Final Year students of Gandhi
Medical CollegeBhopal
3
Cornea
4
Anatomical facts
  • The anterior 1/6th transparent avascular
    structure covered anteriorly by tear film and
    exposed to external environment . The posterior
    surface is in contact with aqueous humour.
    Corneal epithelium is continuous
  • The junction of cornea and sclera is represented
    by highly vascularized limbus which contains stem
    cells which serves as reservoir of pluripotential
    cells

5
Anatomical facts
  • Measurements of adult cornea
  • Horizontal 11 -12 mm
  • Vertical 9-11 mm
  • Thickness central 0.5 mm
  • peripheral 0.7 1 mm

6
Optical properties of Cornea
  • Dependant on
  • Transparency
  • Smoothness of surface
  • Contour
  • Refractive index
  • Refractive power of Cornea is 40 44 Diopter
    (i.e. 2/3rd of total refractive power of eye)

7
Maintenance of corneal integrity
  • Maintenance of normal corneal integrity
  • 1. Role of environmental (Chemical/ biological
    agents/physical events of outside world affect
    integrity)
  • 2. Epithelial maintenance limbal stem cells and
    basal cells are capable of proliferation

8
Maintenance of corneal integrity
  • 3. Epithelial movement intracellular signal,
    transduction, fibronectine integrin system,
    proteolytic enzymes, hyaluronin and growth factor
    play an important role in wound healing
  • 4. Neural regulation
  • 5. Stromal maintenance

9
Introduction
  • Microbial Keratitis is defined as infectious
    Corneal ulcer due to proliferation of
    microorganisms (including bacteria, fungi,
    viruses and parasites) associated with
    inflammation and corneal tissue destruction.
  • It is potentially sight threatening condition and
    should be considered as ocular emergency.

10
Bacterial Keratitis
  • Bacterial Keratitis is most common cause of
    suppurative corneal ulceration. There are no
    specific clinical signs to help confirm a
    definite bacterial cause in Bacterial Keratitis.
  • Identification of risk factors and assessment of
    the distinctive corneal findings will help in
    determination of potential etiologies.

11
Host Defense and Risk Factors
12
Defense of Ocular Surface
  • Normal Defense mechanisms
  • Eyelids
  • Tear film proteins (Secretory immunoglobulins,
    complement components, and various enzymes
    including lysozyme, lactoferrin, betalysins,
    orosomucoid and ceruloplasmin have antibacterial
    effect)
  • Corneal epithelium
  • Normal ocular flora
  • Conjunctival mucosal associated lymphoid tissue
    (MALT) which is present in subepithelium

13
Risk Factors
  • Compromised normal ocular surface
  • Chronic colonization and infection of the eyelid
    margin and lacrimal outflow system can predispose
    cornea
  • Chronic epiphora by reducing concentration of
    certain antibacterial substances.
  • Dry eye

14
Risk Factors
  • 5. Presence of N Gonorrhoeae, C Diphtheriae,
    Hemophilus Aegyptius and Listeria Monocytogenes
    they can penetrate intact corneal epithelium.
  • 6. Compromised corneal epithelium as in cases of
    contact lenses users, corneal trauma, corneal
    surgery bullous keratopathy.
  • 7. Absence of normal conjunctival flora.

15
Risk Factors
  • 8 Biofilm- is a slimy layer composed of organic
    polymers produced by embedded bacteria on contact
    lens, it protects bacteria from antibacterial
    substances and provide a nidus for infection.
  • 9. Corneal anaesthesia
  • 10. Abuse of topical anaesthetic solution

16
Risk Factors
  • 11. Local immune suppression as due to topical
    corticosteroids
  • 12. Previous viral infection
  • 13. Drugs used in viral keratitis
  • 14. Corneal hypesthesia

17
External Risk Factors
  • Trauma (Nocardia)
  • Exposure to contaminated water or solutions
  • Chronic abuse of topical anaesthetic solution
  • Crack Cocaine smoking (disrupting corneal
    epithelium via associated cellular and neuronal
    toxicity.

18
Predisposing Systemic Conditions
  • Malnutrition
  • Diabetes
  • Collagen vascular diseases
  • Chronic alcoholism

19
Etiological Factors
  • Inflammation of Cornea (Keratitis) may develop as
    a result of
  • 1. Exogenous infection Mostly traumatic, the
    object causing injury may carry infection to
    cornea or may come from conjunctival sac
    (infecting abraded cornea)
  • 2. Endogenous Infection (inflammation) this is
    immunological in nature eg. Phlyctenular
    keratitis caused by tubercular or staphylococcal
    hypersensitivity and interstitial keratitis
    related to measles or syphilis. These conditions
    are commonly noticed at corneal margin (Marginal
    Keratitis or Marginal Corneal Ulcer)

20
Etiological Factors
  • 3. Spread of Infection from neighboring
    structures due to anatomical continuity.
  • From conjunctiva to corneal epithelium (eg.
    Trachoma and Vernal Keratoconjunctivitis)
  • From Sclera to corneal stroma (eg. Sclerosing
    Keratitis) and
  • From Uveal tract to corneal endothelium (eg.
    Herpetic Uveitis causing endothelitis)

21
Classification
  • I. According to location
  • a. Superficial
  • b. Deep
  • II. According to Etiology
  • a. Infective
  • b. Immune mediated
  • c. Traumatic
  • d. Neoplastic
  • e. Degenerative

22
Bacterial Keratitis
  • Two forms
  • Central Keratitis
  • Peripheral Keratitis.

23
Corneal Ulcer
  • Superficial Purulent Keratitis (Bacterial Corneal
    Ulcer)
  • Caused by organisms which produce toxins causing
    tissue death i.e. necrosis characterised by pus
    formation. Such purulent keratitis is usually
    exogenous due to infection by pyogenic bacteria
    such as pseudomonas, staphylococcus aureus and
    albus, pneumococcus, N. gonorrhoeae and C.
    diphtheriae

24
Corneal Ulcer
  • Presence of N Gonorrhoeae, C Diphtheriae,
    Hemophilus Aegyptius and Listeria Monocytogenes
    they can penetrate intact corneal epithelium.
  • Otherwise most of the bacteria including
    Pneumococcus is capable of producing corneal
    ulcer when epithelium is damaged

25
Pathogenesis
  • Steps
  • Corneal abrasion
  • Infection by microorganism in presence of
    predisposing factor(s). The predisposing factors
    are trauma, long term use of steroids,
    misdirected eye lashes, mal-apposition of lids,
    entropion, lagophthalmos, contact lens wear,
    bullous keratopathy, poor hygienic condition,
    malnutrition, ocular surface disorders, vitamin A
    deficiency, causing corneal necrosis
    (Keratomalacia), corneal edema and trigeminal
    nerve paralysis (Neurotropic keratitis)

26
Pathogenesis
  • 3. Localized necrosis of superficial layers of
    cornea
  • 4. Formation of sequestrum with disintegration.
    It cast off in conjunctival sac
  • 5. Desquamation of corneal epithelium and damage
    to Bowmans membrane (area of epithelial and
    Bowmans denudation is larger than ulcer)

27
Pathogenesis
  • 6. Epithelial regeneration, at times it covers
    the edges and floor area
  • 7. A saucer shaped defect with projecting walls
    above the normal surface due to swelling of
    tissue resulting from fluid imbibition by corneal
    stroma
  • 8. Surrounding area is packed by leucocytes,
    seen as gray zone of infiltration. This is
    progressive stage.

28
Pathogenesis
  • 9. Necrotic material fall off- ulcer becomes
    larger -gt infiltration and swelling reduce and
    disappears -gt margin becomes smooth, floor also
    looks smooth and transparent. This is regressive
    stage.
  • 10. Vascularization develops from limus to
    corneal ulcer to restore lost tissue and to
    supply antibodies.

29
Pathogenesis
  • 11. Vascularisation is followed by cicatrization
    due to regeneration of collagen and formation of
    fibrous tissue
  • 12. Newly formed fibres are laid down
    irregularly, not conforming to normal pattern of
    stromal fibres. Therefore this fibrous tissue
    reflects light irregularly. The scar tissue is
    more or less opaque. Some vessels may persist in
    large scar

30
Pathogenesis
  • 13. Bowmans membrane never regenerates and
    whenever it is destroyed some degree of corneal
    opacity remains
  • 14 Corneal opacity may clear with time especially
    if it is not dense. The vascularization plays
    part in clearing corneal opacity
  • 15. The scar tissue usually fill the gap exactly,
    but some deficiency may remain giving rise to
    formation of corneal facet. The corneal facet may
    be transparent and may be associated with marked
    diminution of vision

31
Pathogenesis
  • 16. Diffusion of bacterial toxins into the
    anterior chamber leads to hyperaemia and
    inflammation of the iris and ciliary body
    (Keratouveitis). Polymorphonuclear cells coming
    out from the uveal tissue may gravitate to bottom
    of anterior chamber to form hypopyon.

32
Symptoms of Corneal Ulcer
  • Symptoms are usually marked, they are
  • 1. Diminution of vision, depending on location
    of corneal ulcer
  • 2. Watering (lacrimation)
  • 3. Difficulty in opening eyes especially in
    bright light (photophobia and blepharospasm)
  • 4. Pain and foreign body/ gritty sensation
  • 5. There may be discharge (Mucopurulent /
    purulent)

33
Presentation
  • Clinical signs and symptoms are variable
    dependent on the virulence of the organism,
    duration of infection, pre-existing corneal
    conditions, immune status of host and previous
    use of antibiotics/ steroid
  • Acanthamoeba can cause masquerading syndrome
    mimicking bacterial keratitis.

34
Signs
  • Visual acuity may be affected, depending on
    location of corneal ulcer
  • Edema of lids of affected eye, in severe cases
  • Blepharospasm
  • Ciliary and conjunctival congestion
  • Hazyness / pus may be present in anterior chamber

35
Signs
  • 6. Colour and pattern of iris may be disturbed
  • 7. Cornea loss of transparency the ulcer appears
    yellowish/ grayish pale lesion of varying shape
    /size, breach in continuity of corneal surface,
    ulcer with irregular floor and margins, floor
    appears grayish / grayish pale/ grayish yellow,
    zone of infiltration with projecting swollen
    edges. The surrounding cornea may appear ground
    glass like due to corneal edema

36
Corneal Ulcer
Central Corneal ulcer involving Lower periphery
also
Peripheral Corneal Ulcer
37
Clinical Examination
  • Evaluation of predisposing and aggravating
    Factors
  • A detailed history
  • Prior ocular history
  • Review of related medical problems, current
    ocular medications and history of medication
    allergy

38
Examination
  • Visual acuity
  • An external ocular examination
  • Facial appearance, eyelids, lid closure
  • Conjunctiva, Nasolacrimal apparatus, corneal
    sensation

39
Examination
  • 3. Slit Lamp Biomicroscopy For
  • Eyelid margin
  • Tear film
  • Conjunctiva
  • Sclera
  • Cornea (epithelial defects, punctate
    keratopathy, edema, stromal infiltrates/ulcerati
    on, thinning or perforation)

40
Slit Lamp Examination Contd
  • Location of lesion
  • Density, Size , shape , depth, colour
  • Endothelium
  • Anterior chamber
  • Loose or Broken sutures
  • Signs of corneal dystrophy
  • Signs of previous inflammation

41
Slit Lamp Examination Contd
  • Anterior Vitreous
  • Fluorescein
  • Rose Bengal staining

42
Differential Diagnosis
  • Differentiate from Non-infectious causes of
    infiltrates
  • Fungal
  • Protozoal
  • Nematodes
  • Viral infections, HSV, VZV, EBV
  • Contact lens infiltrates
  • Collagen Vascular Diseases

43
Differential Diagnosis
  • 7. Sarcoidosis
  • 8. Severe Rosacea
  • 9. Allergic Conditions
  • 10. Corneal Trauma , FB and Loose sutures

44
Complications of Corneal Ulcer
  • Spread of ulcer horizontally and depth-wise,
    leading to thinning of cornea
  • Bulging of descemets membrane (Keratocele or
    Descemetocele). This appears as transparent
    vesicle surrounded by grayish zone of
    infiltration. Bulging of descemets membrane
    represents condition of impending perforation of
    cornea

45
Complications of Corneal Ulcer
  • 3. Perforation of ulcer is generally caused by
    sudden exertion such as coughing, sneezing,
    straining at stool or firm closure of eyes.
    Exertion causes rise of blood pressure and
    results in increase in intra-ocular pressure
    (IOP). Weak area of ulcer is unable to support
    the increased IOP , gives way and perforation
    develops

46
Complications of Corneal Ulcer
  • PERFORATION OF CORNEAL ULCER
  • Complications of perforation may be serious and
    sight threatening
  • Peripheral perforation Iris is thrown forward
    -gt opening is occluded -gt anterior chamber is
    formed , scarring takes place
  • a. Iris may be pushed back to normal position or

47
Complications of Corneal Ulcer
  • b. Iris may remains adherent to corneal scar
    (anterior synechia)
  • If peripheral perforation is large the
    pupillary border of iris prolapse through
    opening. Exudation takes place on prolapsed
    tissue -gt an adherent leucoma forms (it may be
    flat or bulging)

48
Complications of Corneal Ulcer
  • B. Central perforation small central
    perforation -gt anterior chamber collapse
  • -gt lens comes in contact with corneal
    endothelial surface -gt anterior capsular cataract
    -gt repeated healing and perforation leading to
    corneal fistula formation

49
Complications of Corneal Ulcer
  • C. Sloughing of whole cornea prolapse of iris
    -gt pupillary block and exudation on iris -gt
    pseudocornea formation (iris covered with
    exudates , formation of fibrous tissue and
    formation of scar tissue) -gt anterior chamber
    anatomy is lost , angle of anterior chamber is
    occluded leading to secondary glaucoma -gt
    anterior staphyloma (an ectatic cicatric with
    incarceration of iris). Anterior staphyloma may
    be partial or total.

50
Complications of Corneal Ulcer
  • In case of sudden large perforation lens may
    subluxate or thrown out due to rupture of
    suspensory ligaments. Lens and vitreous may
    prolapse through perforation. Intraocular
    haemorrhage may occur due to dilatation and
    rupture of intra-ocular blood vessels due to
    sudden hypotony. This may lead to vitreous
    haemorrhage , choroidal , sub-retinal or
    sub-choroidal haemorrhage. In elderly patients
    there may be expulsive haemorrhage

51
Complications of Corneal Ulcer
  • D. Intra-ocular purulent infection due to
    perforation bacteria enter in the eye and causes
    purulent iridocyclitis, endophthalmitis and
    panophthalmitis

52
Treatment of uncomplicated corneal ulcer
  • LOCAL TREATMENT
  • 1. Control of infection with appropriate
    antibiotic(s)
  • a. based on clinical judgment
  • b. based on finding of smear examination
  • c. based on culture and sensitivity report

53
Local Antibiotic therapy
  • Antibiotic drops frequently, ointment may be used
    at bedtime in less severe cases. Collagen shield
    or soft contact lenses soaked in antibiotics are
    sometimes used and may enhance drug delivery.
  • Sub-conjunctival antibiotics may be helpful where
    there is imminent scleral spread or perforation
    or in cases where compliance with the treatment
    regimen is questionable

54
Therapeutic Agents
  • No organism identified or multiple types of
    organisms
  • Cefazolin Topical 50 mgm/ml S/c 100 mgm in
    0.5 ml.
  • With Tobramycin / Gentamicin
  • Topical 9-14 mgm/ml S/c 20 mgm in 0.5 ml.
  • Fluroquinolones 3 mgm/ ml

55
Therapeutic Agents
  • 2. Gram Positive Cocci
  • Cefazolin Topical 50 mgm/ml S/c 100 mgm in
    0.5 ml.
  • Vancomycin Topical 15 - 50 mgm/ml S/c 25 mgm
    in 0.5 ml.

56
Gram Negative Rods
  • Tobramycin / Gentamicin
  • Topical 9-14 mgm/ml S/c 20 mgm in 0.5 ml.
  • Ceftazidime Topical 50 mgm/ml S/c 100mgm in
    0.5 ml.
  • Fluroquinolones 3 mgm/ ml

57
Gram Negative Cocci
  • Ceftriaxone Topical 50 mgm/ml S/c 100 mgm in
    0.5 ml.
  • Ceftazidime Topical 50 mgm/ml S/c 100 mgm in
    0.5 ml.
  • Fluroquinolones 3 mgm/ ml

58
Treatment of uncomplicated corneal ulcer
  • 2. Cycloplegic and mydriatic drug atropine 1
    or cyclopentolate 1 or Homatropine 2. These
    drugs prevents ciliary spasm, relieves pain,
    prevent dangerous results of iridocyclitis,
    breaks adhesions and prevent synechia formation

59
Treatment of uncomplicated corneal ulcer
  • 3. Cleanliness Irrigation with luke warm normal
    saline or 2 luke warm boric acid solution to
    remove conjunctival discharge and necrotic
    material
  • 4. Application of heat provides comfort and
    causes vasodilatation
  • 5. Protection of eye from external environment
    with dark glasses

60
Treatment of uncomplicated corneal ulcer
  • Steroids must not be used in presence of active
    infected corneal ulcer
  • In cases of progressive corneal ulcer despite
    routine therapeutic treatment, the following
    measures be considered
  • Scraping of ulcer floor followed by cauterization
    with pure (100) carbolic acid or 10-20
    trichloracetic acid. Povidone Iodine can also be
    used for cauterization

61
Systemic Treatment
  • Systemic Antibiotics consider in sever cases
    with scleral or intra-ocular extension of
    infection or with impending or frank perforation
    of the cornea
  • Systemic antibiotic therapy is necessary in
    cases of Gonococcal keratitis due to its
    fulminating nature and systemic involvement

62
Systemic Treatment
  • 2. Analgesic anti-inflammatory
  • 3. Supportive treatment
  • 4. Acetazolamide Tab is added in cases of
    impending perforation or perforated corneal ulcer
    and in cases where there is raised intra-ocular
    tension (in dosage of 250 mgm upto four times a
    day)

63
Non-responsive / Progressive Corneal Ulcer
  • TREATMENT
  • Re-evaluate for
  • Drug toxicity
  • Non-infectious causes or
  • Unusual organisms such as non-tubercular
    mycobacteria, Nocardia or acanthamoeba should be
    suspected
  • Modification of anti-microbial therapy
  • Therapeutic keratoplasty may be undertaken

64
Indolent / Non-healing Ulcer
  • Consider debridement of necrotic corneal stroma
    and
  • Frequent lubrication and/or
  • Temporary tarsorrhaphy

65
Treatment of Keratocele or Descemetocele
  • Continue use of local antibiotics, atropine, add
    topical antiglaucoma medication (like Timolol or
    Betaxolol) or add systemic acetazolamide, bandage
    contact lens is beneficial. All forced expiration
    like coughing, sneezing, blowing of nose etc must
    be avoided

66
Treatment of perforated corneal ulcer
  • Rest
  • Continue treatment of corneal ulcer with
    modification, i.e. firm bandage or bandage
    contact lens
  • All forced expiration like coughing, sneezing,
    blowing of nose etc must be avoided
  • Use of tissue adhesive (Glue) N-butyl 2-ethyl
    cyanoacrylate
  • Therapeutic penetrating keratoplasty or
    conjunctival flap

67
Adjunctive Therapy
  • Cyanoacrylate tissue glue
  • Therapeutic Contact Lenses

68
Surgical Treatment
  • Conjunctival flap In recalcitrant bacterial
    keratitis
  • Penetrating Keratoplasty (PKP)
  • Large central ulcer , presenting late
  • History of previous ocular surgery
  • Injudicious use steroid treatment
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