11.3.2 Cornea Flashcards
Physiology of cornea
- Window, strong convex lens
- Nutrition – no blood vessels!!
- Dense sensory innervation
- Transparency:
a) Uniform structure (collagen fibres)
b) Avascular
c) Relative dehydration
Corneal ulcerations in general
Symptoms
Signs
Symptoms
- Pain, photophobia
- Tearing
- Decreased vision, haloes
Signs
- Red, injected eye
- Epithelial defect – will stain with fluorescein (green)
- ±Infiltrate (neurophils, inflam cells)
- ±Hypopyon (puss in anterior chamber)
- ? Corneal sensation
Epidemiology of central corneal ulceration
- Usually bacterial or fungal infection
- Intact epithelium = barrier against most organisms
- Exceptions: N. gonorrhoea, N. meningitides, C. diphtheriae & H. influenzae
- Compromised epithelium →inoculation→ central spread →thinning
- Descemet membrane often resists perforation (very thin but very strong)
Bacterial keratitis common organisms
Common organisms:
- Strep pneumoniae
- Pseudomonas
- Staphylococci
Bacterial keratitis complications
- Thinning (dimple in middle)
- Opacification
- Neovascularisation (really bad for transplant)
- Perforation (organisms then get access to inside of eye)
- Endophthalmitis
→ permanent loss of vision
Fungal keratitis
- Usu history of injury involving organic matter (autumn or spring time)
- Indolent (don’t grow fast), greyish, feathery, satellite lesions (infection on other site than where lesions is)
- Often hypopyon
- Hyphae on scrapes, cultures take ages
Primary herpes simplex keratoconjuntivitis
- Viral
- First infection
- Usually kids/young people
- Vesicular skin rash
- Follicular conjunctivitis
- Punctate epithelial keratitis → dendrite
Recurrent Herpes Simplex keratitis
- Irritated, mild → mod tearing & photophobia
- Dendritic ulcer
- ↓↓ corneal sensation (usually not absent!)
- Geographic if neglected/steroids
Have pt ever had cold sores on lips?
Herpes zoster
- HZO (Opthalmicus) ⇔ Ophthalmic branch of trigeminal nerve
- Hutchinson sign ⇔ ↑ chance of eye involvement (if rash on side and tip of nose) -> will also have papillary involvement
Should you give steroid for pt with ulcer?
Steroids are ABSOLUTELY contra‐ indicated in herpetic keratitis as far as the general practitioner is concerned
Chlamydia keratitis
- STI
- Usually accompanies inclusion conjunctivitis
- Follicles
- Pre‐auricular lymph nodes
- Small, peripheral corneal infiltrates
Marginal keratitis
- Usually Ag‐Ab reaction
- Often Staph blepharitis
- Marginal infiltrates → ulcerate, vascularise
- If blepharitis (‐), consider collagen vasc disease
- 2,4,8,10 position of eye (where eyelid meets cornea)
Phlyctenulosis
- Delayed hypersensitivity to bacterial antigen
- whole eye is not affected (if not treated can move on to rest of eye)
- TB or Staph
- delayed hypersensitivity reaction
- Conj or cornea
- Peripheral pustule → ulcerates
Vit A deficiency
- Dry eye (Xerophthalmia)
- Conjunctiva keratinises (Bitot spots)
- Cornea dull → softens (keratomalacia) → perforates
- night blindness
- causes corneal ulceration
Neurotrophic ulceration
- Damage to sensory nerve supply (V1)
- Epithelial oedema + punctate erosions → enlarge
- Ulceration ± 2 infection
- Refer!
