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Microbial Keratitis


  1. Bacterial Keratitis: -
    1. commonest organism is staphylococcus*
    2. Commonest in India – Streptococcus pneumonia*
Pathogens which can penetrate intact* cornea (Epithelium) are
  1. Neisseria gonorrhoeae and meningitidis           
  2. Corynebacterium diphtheriaea
  1. C/F:   
    1. Photophobia earliest symptom
    2. Pain                 
    3. Blepharospasm
    4. Ciliary congestion    
    5. Corneal ulcer with or without stromal suppuration
    6. Corneal rings – In gram – negative infection due to infiltrates in stroma in response to endotoxins
    7. Hypopyon – May or may not be present (in pneumococcal keratitis – called “ Ulcus serpens”)
  2. Sequelae:  
  3. Long standing ulcerationcorneal thinning corneal perforation iris may adhere to it ( leucoma adherens) Pseudo cornea formation.  
  4. Treatment
    1. Topical Antibiotics For both Gram-ve and Gram +ve ( as per investigation)
    2. Fortified topical antibiotics:-
      1. Gentamycin      – 15 mg / ml
      2. Cefuroxime       – 50 mg/ ml
    3. Sub- conjunctival injections
    4. Oral antibiotics – ciprofloxacin has excellent intraocular penetration
    5. Topical cycloplegics

Recent Advances:
Now a days-     
Concentrated cefazolin 5% (fortified)
Concentrated tolramycin 1.3%) are used.

  1. Viral Keratitis
    • HSV keratitis                   
    • HZO
    1. HSV Keratitis Viral infection is associated with decreased corneal sensation
      1. C/F:          
        1. Blepharo conjunctivitis ( self- limited ;  occurs in primary ocular infection)
        2. Keratitis:
          Epithelial Disease
          1. Dendritic ulcer* -  The bed of ulcer stains with fluorescein and virus laden cells at the margin of ulcer take up rose bengal
          2. Geographical ulcer* with stromal infiltrate
          3. Stromal Necrotic Keratitis* Due to direct viral invasion and destruction. Stroma has cheesy, necrotic appearance with associated uveitis
          4. Disciform keratitis* -  Endothelitis
            1. Neurotrophic – Also called Metaherpetic keratitis. Trophic ulcers are not due to active viral disease but due to denervation and drug toxicity
      2. Treatment : 
        1. Antiviral agents: 
        2. Most common – Topical Acyclovir, Valacyclovir, Famciclovir
        3. Other -  Trifluorothymidine , adenine arabinoside , Idoxuridine
    2. HZO: Herpes zoster ophthalmicus
      Hutchison’s rule / sign- Involvement of nasociliary nerve(Tip of the nose) is generally associated with corneal involvement
  • Corneal lesions:
  1. Punctate epithelial keratitis – may be associated with filamentary keratitis
  2. Micro dendritic ulcers ( Pseudo dendrites) * (No Knobs at end)
  3. Nummular keratitis* – Involves superficial stroma
  • Cranial nerve palsies
  • Optic neuritis
  • Post-herpetic neuralgia
Treatment:  1. Oral and Topical antivirals and topical steroids
  1. Fungal Keratitis – (Kerato mycosis)
Fungal infection – Generally associated with trauma to eye with vegetable matter
Most common fungi in India – Aspergillus fumigatus*
  1. C/F : Symptoms:  Patient is less symptomatic compared to the signs of disease
  2. S/S:
    1. Mild watering, photophobia, redness, pain, mild discharge
    2. Fungal ulcer- dry like parchment paper*
    3. Greyish white colour
    4. Wessely ring-around central lesion*
    5. Satellite* lesions in periphery
    6. Associated hypopyon is dirty yellow, infected and fixed
  3. Investigation:
    1. Smear examination
      1. 10% KOH wet preparation               
      2. Gomori methamine silver stain
    2. Culture – Sabouraud’s glucose agar, Czapek- dox medium, liquid brain- heart infusion broth
  4. Treatment: 
    1. Antifungal therapy – commonly used drugs are
    2. Topical – Natamycin , fluconazole (0.2%)
    3. Oral – Fluconazole, Itraconazole in immunocompromised patients, diabetics, stromal                             lesions, endothelial plaques etc.
Local Antifungal agent used in corneal fungal infection? (AIIMS May 08)
  1. Silver sulfadiazine                           
  2. Neomycin
  3. Griseofulvin                                    
  4. Natamycin

Ans. 4. Natamycin

  1. Acanthamoeba Keratitis
    Contact lens wearers who use tap water* to store lenses are at increased risk of acanthamoeba keratitis
  1. Clinical Features  
    1. Blurred vision and pain which is characteristically severe and disproportionate to the extent of ocular involvement
    2. Multifocal patchy anterior stromal infiltrates stromal ring abscess
    3. Pseudo dendrites*
    4. Stromal thinning and descemetocele*
    5. Radial Keratonuritis (Pain out of propotion to ulcer)
  1. Investigation: Smear Examination – 
    1. Calcofluor white* : cysts stain bright green
    2. KOH mount
    3. Lactophenol blue
  1. Treatment:  
    1. Combination of dipropamidine and polyhexamethylene biguanide drops (PHMB) *
    2. Other drugs –     
      1. Propamidine isethionate      
      2. Neomycin
  1. Interstitial Keratitis
    Delayed type hypresensetivity reaction in corneal stroma
  1. Causes: Most common now a days is idiopathic / Herpethice
    1. Congenital syphilis* – Deep vascularization – “Salmon patch cornea”
    2. Tuberculosis*
    3. Leprosy         
    4. Sarcoidosis
    5. Filariasis
    6. Cogan’s syndrome* – Associated with deafness
  2. Treatment  of underlying disease.
    Ectatic Disorders
  1. Ectatic Disorders
  1. Keratoconus                        
  2. Posterior keratoconus         
  3. Keratoglobus                       
  4. Pellucid marginal degeneration
Conical cornea
Non- inflammatory,  bilateral progressive  ectasia with thinning of the central cornea
  1. Irregular myopic
  2. C/F:
  1. Impaired vision – due to progressing myopia and astigmatism
  2. Retinoscopy – irregular scissors reflex
  3. Keratometry – Irregular astigmatism
  4. Slit- lamp biomicroscopy –
    1. Vogt’s lines – vertical folds or tears in descemets membrane
    2. Prominent corneal nerves
  5. Munson’s sign* – Bulging of lower lid in down- gaze
  6. Fleischer’s ring* – iron line encircling base of cone epithelium
  7. Acute Hydrops*-  Sudden hydration of corneal stroma due to rupture of Descemet’s membrane
  8. Investigation of choice : Corneal topography (orbscan/ pentacam)
  1. Spectacles (cylindrical correction for astigmatun
  2. Rigid Gas permeable contact lens (RG) Special lenses → Rose K
  3. Penitrating Keratopliasty in optical sear
  4. C3 XL-Corneal collagen cross linking-to arrest progreisom
  5. INTACS for moderate Keratoconus
  1. Keratoplasty
    Replacement of diseased cornea by a graft of homologous tissue
  1. Penetrating Keratoplasty – Replacement of whole (Full- thickness cornea)
    Most common indication of PK
    1. Corneal opacity-India
    2. Corneal dystrophy western world (PK is commonly performed for macular corneal dystrophy).
  2. Types:
    1. Optical improve vision replace opaque cornea with clear donor tissue
    2. Tectonic restore corneal anatomy in stromal thinning and descmetoceles
    3. Therapeutic removes infected corneal tissue unresponsive to antimicrobial / antiviral rx
Lamellar Keratoplasty- Replacement of partial thickness of cornea - Anterior Laminar – Tillstocoma (DALK) Deep Anteior Lamellar Keratoplasty
  • Posterior Laminar
  • DSAEK (DM+Stroma+Endothelium) Deep Stromal Automated Endothelial Keratoplasty
  • DMEK (Only DM+Endothelium) Descemet’s Membrane Endothelial Keratoplasty

Corneal Degenerations:
  1. Arcus senilis*- B/L lipid degeneration which starts in superior and inferior limbus, forms a ring
  2. Cornea guttata.*- Warts/ excresences of Descemets Membrane in central cornea; Similar lesions in periphery Hassall – Henle bodies. Seen in old age M/C Cornal degeneration
Encrescines or warte of DM
Gattata Central cornea Fuch’s endotheal
Hassal henle bodie Periphal cornea Old age
  1. Band shaped Keratopathy (BSIC)
    BBC-BSK-BOWMAN’S Layer-Calcium
    1. Etiology
      1. Chronic uveitis (particularly in children-JRA).
      2. Increased serum calcium or phosphorus levels (Sarcoidosis)
      3. Idiopathic-In elderly.
b.  ​​Clinical Features
  1. Calcium deposition characteristically showing interpalpebral distribution of the lesions with a clear space separating the sharp margin of the band from the limbus.
  1. Treatment
  1. Topical chelation                                 
  • Sodium versenate
  • EDT A
  1. Photo Therapeutic keratectomy- Excimer laser
  1. Spheroidal Degeneration ( Lipid droplet Keratopathy/ climactic droplet Keratopathy)
  2. Salzmann's Nodular Degeneration
  1. Etiology
    Occurs secondary to chronic keratitis especially trachoma and phlyctenulosis.
  2. Clinical Features
    1. Superficial stromal opacities, grey in colour which form nodules and elevate the corneal epithelium.
  1. ​Peripheral Corneal Disorders
    1. Dellen
      It consists of localized* area of corneal thinning which occurs as a result of localized tear film instability.
    2. Marginal Keratitis
  • Also called Catarrhal ulcer occurs at 2,4,8,10 o clock Portion of Cornea
  • Caused by hypersensitivity reaction* to staphylococcus exotoxins (patients of chronic staphylococcal   blepharitis).
  1. Treatment
    • Short course of topical steroids
    • Tt of associated blepharitis.
  1. Phlyctenuloses or Phlyctenular Conjunctivitis
    Corneal phlycten may lead to fascicular ulcer, which may then form ring ulcer.
  2. Mooren's Ulcer
    1. It is a peripheral ulcerative keratitis caused by ischemic necrosis* due to vasculitis of limbal vessels (caused by the enzymes-collagenase and proteoglycans produced from adjacent conjunctiva),
    2. Calcium deposited in Bowman’s layer separated by corneal Nerves-Swiss Cheese Pattern
i. Topical steroids
ii. Systemic therapy:
  • Steroids                        
  • Cyclosporin                  
   Conjunctival Excision-Excision is done 3 mm from the limbus and parallel to the ulcer.
  1. Miscellaneous Keratopathies
  1. Vortex Keratopathy
  1. Also called Cornea Verticillata
  2. Clinical Feature: Symmetrical, bilateral, grayish or golden corneal epithelial deposits which
  1. Etiology
    1. Fabry's disease (Glyco lipidosis)                      
    2. Chloroquine                    
    3. Amiodarone
    4. Tamoxifen.                                                        
    5. Indomethacin                
    6. ​Chlorpromazine                             
  1. Crystalline Keratopathy
    1. Chrysiasis - Deposition of gold in corneal stroma  in patients of rheumatoid arthritis.
    2. Cystinosis
      1. Widespread tissue deposition of cysteine crystals*
      2. It's a hereditary disorder (autosomal recessive*) leading to defect in its lysosomal transport.
  2. Corneal Dystrophy
    inherited, bilateral , stationary or slowly progressive corneal alterations that develop in absence of inflammation.
Classification (Latest classification - IC3D Classification)

  1. Edithelial Dystrophies
    1. Microcystic EBMD-Most common Characterized by Recurrent Corneal Erosions due to lack of Hemidesmosomes. Painful (Mapdot Fingerprints)
    2. Meesmann
  2. Stromal Dystrophies
  1. Macular (AR,  MPS deposits)Alcian Blue stain
  2. Granular (AD, Hyaline granule deposits) Masson’s trichrome stain
  3. Lattice (AD, Amyloid deposit) Congo Red Stain                                             
    Marilyn Monroe Always Gets Her Men from LA & California
  4. Shnyder crystalline dystrophy: abnormal cholesterol deposition
    Remember arm: that is AR inheritance in macular-least common
  1. Posterior Dystrophies
  1. Fuchs’ endothelial-MC (seen in elderly pts)                
  2. Posterior polymorphous
  3. Congenital hereditary endothelial dystrophy
  1. Treatment
    Initial treatment may include hypertonic eye drops and/or ointment to reduce the corneal edema and may offer symptomatic improvement prior to surgical intervention. Suboptimal vision caused by corneal dystrophy usually requires surgical intervention in the form of corneal transplantation. Penetrating keratoplasty is commonly performed for extensive corneal dystrophy.
  1. Neurotrophic Keratopathy
  1. In anaesthetic cornea*. Loss of neural influences, causes edema and exfoliation of epithelial cells by altering their metabolic activity
  2. Causes- HSV,HZO, DN, Leprosy, section of (Trigeminal - 5th nerve)*.

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