Mycotic(Fungal) Corneal Ulcer

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Mycotic(Fungal) Corneal Ulcer

MC mode of infection	Injury by vegetative material(crop leaf,thorn,wooden stick)
etiology	Aspergillus fumigatus(MC in india), Candida albicans, Fusarium
Symptoms	Same as bacteria but less severe
Signs (prominent) filamentous keratitis with fluffy edges – there is a large epithelial defect, and folds in Descemet membrane	yellowish white dry looking ulcer with elevated rolled out feathery & hyphate margins, Feathery fingerlike extensions, Satellite lesions are seen, Sterile immune ring(yellow line) of Wessely, Dense immobile Non sterile hypopyon(pseudo hypopyon), ring infiltrate, with satellite lesions and a hypopyon Perforation is rare, Vascularization absent
Hypopyon in fungal keratitis contain	Fungal filaments
staining	KOH Smear, Gomori's methenamine silver(GMS) stain
Wet KOH shows	Filamentous fungi(branched septate hyphae) - Aspergillus fumigatus,Fusarium, Non filamentous(yeast like) - Candida
culture	Salon agar, Brain heart infusion broath
Treatment	5% Natamycin eye drops(DOC) - filamentous fungi, Amphotericin B(DOC) - yeast lie fungi, Fluconazole - candida Itraconazole eye drops, Silver sulfadiazine used earlier, Systemic therapy for severe cases 1% Atropine ointment, Anti glaucoma drugs
Steroids are contraindicated in	Both bacterial & fungal ulcers
If contact lens wearers develop keratitis	Start antibiotic drops immediately, Discontinue lenses
For overwear syndrome	Avoid wearing contact lenses for 48-72 hours
MC fungus affect lids	Candida albicans

Bacterial Corneal Ulcer/Hypopyon

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Bacterial Corneal Ulcer/Suppurative/Purulent Corneal Ulcer &

Hypopyon

Predisposing factors for bacterial corneal ulcer	Trauma,foreign body,entropion,trichiasis,contact lens use,chronic dacryocystitis,bullous keratopathy
Organisms invading injured cornea	Staphylococcus aureus, Streptococcus epidermis, Pneumococcus, Pseudomonas, Moraxella, Enterobacterias(E.coli,Proteus,Klebsiella)
Organism invading intact corneal epithelium	Neisseria gonorrhoeae, Neisseria meningitides, Corynebacterium, Listeria species, Haemophilus aegyptus
MC bacterial cause of keratitis	Staphylococcus aureus
MC bacterial cause of keratitis in a contact lense wearer	pseudomonas
MC viral cause of keratitis	HSV
The most important symptoms of bacterial corneal ulcer	Pain,lacrimation,foreign body sensation,conjunctival ingestion,photophobia,blurred vision
Earliest symptom	photophobia
Ulcer appearance in bacterial ulcer	Wet looking greyish white ulcer with distinct margins
Management of bacterial corneal ulcer	Topical antibiotics, atropine/cycloplegics(to relieve ciliary spasm,to prevent posterior synechiae), Anti glaucoma drugs
Hypopyon	Accumulation of polymorphonuclear leukocytes in the lower angle of anterior chamber
Most dangerous organisms producing hypopyon	Pseudomonas pyogenes, pneumococcus
Rapid corneal perforation	pseudomonas
Hypopyon corneal ulcer/ulcus serpens	pneumococcus
Corneal ulcer with hypopyon	Any other cause other than pneumococcus
Hypopyon in bacterial cause is	sterile(by toxin)
Hypopyon in fungal cause	Non sterile

Cornea General Features

CORNEA GENERAL FEATURES

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Anatomy of Cornea

Anterior surface	elliptical
Posterior surface	circular
Corneal horizontal diameter of both surfaces in  adult	11.7mm
Corneal vertical diameter of anterior surfaces in  adult	11.7mm
Corneal vertical diameter of posterior surfaces in  adult	10.6mm
Cornea diameter at birth	10mm
Cornea attains adult diameter	2 years
Thickness of cornea at centre	0.5 – 0.6 mm
Radius of curvature on anterior surface & posterior surface of cornea	7.8 mm & 6.5 mm
The vertical meridian of cornea is 0.05 steeper   than the horizontal meridian	Astigmatism with the rule
Refractive power	43-44 D(3/4th of total dioptric power of eye)
Refractive index	1.376
Most of refraction in eye occur at	Anterior surface of cornea(air-tear interface)
Megalocornea	The horizontal diameter is of adult size at birth or >/ 13 mm after the age of 2 years
Megalocornea	Marfan syndrome Ehler danlos syndrome Down syndrome Apert syndrome
Microcornea means diameter less than	10 mm
Microcornea	Autosomal dominant associated with hypermetropia, associated with fetal alcohol syndrome
Long collagen fibres with wide spacing between them	Cornea
Critical angle for cornea air interface	46*
Epithelium of cornea	Stratified squamous non keratinizing
Corneal epithelium	Hydrophobic
Bowman’s membrane	Once destroyed,doesn’t regenerated Not a true membrane,condensed superficial stroma
Stroma (substantia propria)	Occupies 90% of thickness Consists of collagen fibres in hydrated matrix of proteoglycans
Dua’s layer is between	Corneal stroma and descemet membrane
Termination of descemet membrane	Ring of schwalbe
Endothelium	Single layer of flat polygonal cells Cell density - around 3000 cells/mm2 in young adults Metabolically active layer Has active pump mechanism Most important layer in maintaining transparency Regeneration occurs rapidly after injury(decompensation occurs only after >75% cells are lost Krukenberg spindle is seen
Regeneration of corneal epithelial cells from	Palisade of Vogt
Corneal transparency is due to	Homogeneity of refractive index throughout the epithelium avascularity, Peculiar arrangement of lamellae,Uniform spacing of collagen fibrils in stroma Unmyelinated nerve fibres Relatively dehydrated state Na+ K+ pump,Bicarbonate dependent ATPase,Na+/H+ pump Normal IOT
Ion pump in corneal endothelium is necessary for maintaining transparency. it can be blocked by	Inhibition of anaerobic glycolysis
Avascular coat in eye	Cornea
The most actively metabolizing layers of cornea	Epithelium & Endothelium
Cornea receives nutrition form	Atmosphere, aqueous humour,perilimbal capillaries
Corneal vascularization is associated with	Riboflavin deficiency
Corneal neovascularization is caused by	Graft rejection, Chemical burn, Contact lens usage, Viral
	or fungal keratitis
Corneal neovascularization can be prevented by	Photocoagulation