Cornea Flashcards
Cornea refraction power and thickness
40D (highest in eye)
535-545 um CCT
Cornea nutrient supply
aqueous humour posteriorly
tear film anteriorly
Cornea nerve supply
long ciliary nerve CNV1
Layers of cornea
- Epithelial layer (limbal epithelial stem cells) - REGENERATES
- Bowman’s layer
- Stromal layer - colloagen 1, continuous with sclera
- Descemet layer - collagen 4
- Endothelium
Bacterial keratitis
Organisms: pseudomonas, staph, and strep
Features: unilateral red eye, pain, ↓ VA, mucupurulent discharge, hypopyon, white infiltrates
Mx - scrapings to lab, topical abx fluoroquinolones
complications - perforation in :
Neisseria gonorrhoea
haemophilus influenzae
Corynebacterium diphtheriae
Fungal keratitis causes
immunocompromised: candida
Hx of ocular trauma: filamentous fungi e.g. aspergilus or Fusarium
Candida keratitis sign
small plaque ulcer with expanding infiltrate ‘collar stud’
Filamentous keratitis sign
Feathery branching like infiltrate
Mx of fungal keratitis
Candida keratitis - Voriconazole or amphotericin B drops
Filamentous keratitis - Natamycin drops
Acanthamoeba keratitis
out of proportion pain
Acanthamoeba protozoa
Main risk factor: swimming and contact lens
Sign - Neural ring corneal infiltrates
Mx: polyhexamethyl biguanide (PHMB) or chlorhexidine
HSV keratitis (epithelial)
red eye, foreign body sensation, pain, epiphora
Early - stellate (star shaped) corneal ulcer
Late - Dendritic ulcer under fluorescein dye
mx - topical acyclovir. AVOID STEROIDS
HSV endothelial keratitis
Hypersensitivity to HSV antigen
Painless ↓ VA
Central circular stromal oedema
Wessely ring sign (deposition of immune complexes)
Mx - oral acyclovir
Herpes zoster ophthalmicus
Hutchinson sign (nasociliary nerve involvement)
pseudodendrites - grey and not ulcerated
conjunctivitis and raised IOP
mx - oral acyclovir
Marcus Gunn pupil
RAPD
Interstitial keratitis
inflammation of corneal stroma without epithelial or endothelial involvement
Causes:
1. Syphilis
2. Cogan syndrome (AI, tinnitus and vertigo, sensorineural hearing loss)
3. Lyme disease (Borrelia, tick bites, erythema migrans)
Hutchinson triad (syphilis)
Nothed teath
Interstitial keratitis
sensorineural deafness
Marginal keratitis
Type III hypersensitivity reaction to staph exotoxin
associated with rosacea and blepharitis
typically where cornea touches the eye lid
Peripheral ulcerative keratitis (PUK)
Peripheral corneal inflammation and thinning
Spread posteriorly and centrally
Causes: Infection or AI (Rheumatoid arthritis, polyarteritis nodosa, relapsing polychondritis)
Mx - oral steroids ± DMARD (not topical!)
Ocular rosacea
- posterior blepharitis
- eyelid telangiectasia
- peripheral corneal vascularisation
mx: lubricants, hot compress, oral tetracycline
Filamentary keratitis
Corneal epithelium degeneration > mucus and strands adhering
RF: dry eyes, LASIK, contact lens
Fx: red eye, pain, epiphora, foreign body sensation
**Rose bengal staining - comma shaped lesions move with bilinking
Keratoconus associations
Bilateral irregular thinning of corneal stroma and corneal coning
Association with:
- Marfan syndrome
- Down syndrome
- Ehlers Dansol syndrome
- Leber congenital amaurosis
- Retinitis pigmentosa
Keratoconus features
irregular astigmatism
Munson sign (lower eyelid v on downward gaze)
Vogt striae (vertical striae in corneal stroma)
Oil drop reflex
Scissor reflex
Keratoconus Ix
Steep keratometry
Corneal topography e.g pentacam
Keratoconus complications
Tear in Descement membrane - corneal oedema
Acute hydrops
Keratoconus mx
Mild : spectacle correction with cylindrical lenses
Moderate : rigid contact lens or corneal collagen crosslinking with Riboflavin and UVA
Severe : keratoplasty
**LASIK is contraindicated
Kayser Fleischer ring
Ring copper deposition in Descemet membrane in Wilson disease
Wilson disease
AR deficiency in ceruplasmin - copper deposition
Hepatic fx
Kayser Flescher ring
Mx - chelation via Penicillamine
Band keratopathy
Calcium deposition in Bowman’s layer
Mx chelation with EDTA
Fabry disease
X linked recessive
lysosomal storage dx
Vortex keratopathy and posterior cataracts
Corneal dystrophies
- Epithelial
- Anterior
- Stromal
- Endothelial
Epithelial corneal dystrophies
- Cogan dystrophy (map-dot-fingerprint dystrophy)
- Meesman corneal dystrophy
Anterior corneal dystrophy
Reis Buckler dystrophy (replacement of bowman’s layer with connective tissue)
Stromal corneal dystrophy
‘Maryline Monroe Always Gets Her Men in L. A. County’
‘Marylin Monroe Always’ : Macular dystrophy - Mucopolysaccharide - Alcian blue (staining)
‘Gets Her Men’ : Granular dystrophy - Hyaline materials - Masson trichrome (staining)
‘L. A. County’ : Lattice dystrophy - Amyloid - Congo red (staining)
Endothelial corneal dystrophy
(Fuch’s endothelial dystrophy)
Failure of Na/K pump - fluid accummulation and corneal oedema leading to endothelial cell loss
Fx: elderly woman with blurry vision worse in the morning
specular microscopy > corneal guttate (beaten metal appearance)
increaed central corneal thickness
