Cornea Flashcards
Power of cornea
43-45 D
Refractive index of cornea
1.37
Diameter of cornea
11-11.75
Megalocornea
> 13 mm
Microcornea
<10 mm
How is cornea dehydrated
Barrier function of endothelial cells
Na+/K+ ATPase pump
Number of Endothelial cells in adults
2500-3000 cells/ sq.mm
Number of endothelial cells in children
3500-3000 cells/sq.mm
Number of cells in endothelium which causes hydration of cornea
<500 cells/sq.mm
Features of corneal decompensation (hydration of cornea)
Stromal oedema
Bullous keratopathy
Bullae
Organisms which penetrate intact epithelium
N – Neisseria gonorrhoea N– Neisseria meningitis L – listeria D – diphtheria H – haemophilia S – shigella
Name some investigations related to cornea
Keratometry – curvature of cornea Corneal topography– Plácido’s disc– qualitative assessment Pachymetry- thickness of cornea Specular microscopy-To examine endothelial cells Corneal sensation Microbiological investigation
corneal sensation tests
Qualitative –With a wisp of cotton
Quantitative – aesthesiometre> The length of filament when patient starts feeling sensation
Shorter the length the more pressure is needed and lesser the corneal sensation
Microbiological investigations of cornea
Staining and culture
The main clinical features of keratitis
Pain Redness (ciliary congestion) Photophobia Blepharospasm Discharge
What are the type of redness and what is their pathology
Conjunctival congestion – only conjunctival pathology
Circumciliary congestion – deeper blood vessel
What type of hypopyon present in bacterial keratitis
Sterile hypopyon
Three types of bacterial keratitis
Localised
Perforating
Sloughing
Ulcus Serpens
Hypopion corneal ulcer caused by pneumococcus
2 things NOT to do for infective corneal ulcer
No steroids
No pad/bandage
Management of non-healing ulcer
Debridement
Chemical cauterisation
Conjunctival flapping
What are the local antiseptics used for chemical cauterisation in the management of non-healing ulcer
Trichloroacetic acid
Carbolic acid
Management of impending perforation
Anti-glaucoma drugs
Cyano acrylate blue
BCL – bandage contact lens
Types of contact lens
Soft
Semi soft also known as rigid gas permeable
Most common cause of bacterial keratitis
Staphylococcus aureus
Staphylococcus epidermidis
If there is corneal perforation in 48 hours which organism is it
Pseudomonas
Treatment of bacterial keratitis
Please check your notes
What is the aetiology of fungal keratitis
Drama by vegetative/organic matter
Fungal keratitis also known as
Keratomycosis
Most common fungus infecting cornea
Aspergillus fumigatus
Fusarium
Most common fungus infecting lids
Candida
Most common fungus infecting endophthalmitis
Candida
Most common fungus infecting orbit
Mucormycosis
Compare to bacterial keratitis which is more prominent signs or symptoms in fungal keratitis
Bacterial keratitis – symptoms are more than science
Fungal keratitis – signs are more than symptoms
Examination findings in fungal keratitis
Satellite nodules
hyphae
Unsterile hypopyon
Immune ring
Investigations in fungal keratitis
Staining – KOH Smear, gomori’s methamine, silver stain
Culture – SDA, brain heart infusion broth
Treatment of fungal keratitis
DOC – Natamycin
Nystatin eye ointment
Flucanazole (Candida)
Causes of viral keratitis
HSV (More common)
HZO
Pathognomic feature of viral keratitis
Decreased corneal sensation