21.10: Ophthalmology Flashcards
Corneal ulcer
break in continuity of the corneal epithelium with exposure of the underlying stroma.
What is the difference between a corneal ulcer and ulcerative keratitis?
No difference - they are the same thing.
1
Epithelium
2
Stroma
3
Descemet’s membrane
4
Endothelium
How is corneal transparency retained?
- No keratin, blood vessels or melanin
- Low cell density
- Very regular arrangement of collagen fibrils
- Relatively dehydrated state
How is the relatively dehydrated state of the cornea maintained?
- Epithelium has tight junctions to prevent water from tear film entering
- Endothelium below has Na/K ATPase pump; this pumps ions from the stroma into aqueous humour
What happens if water gets into the stroma of the cornea?
- Corneal oedema develops
- The collagen fibrils are distorted, resulting in opacity
Superficial corneal ulcer
There is loss of the epithelium only.
* Cells slide rapidly over to cover the defect
* Within hours-days there is cell proliferation, migration and adhesion
Describe the process of healing for a stromal ulcer
- This takes longer than a superficial corneal ulcer to heal
- The epithelium must grow over the deficit before the stroma can begin to heal
- Once re-epitheliasisation is complete, fibroblasts migrate in and lay down new collagen
- Requires vascularisation
- Results in scar tissue -> remodelling occurs over time
What are some possible causes of corneal ulcers?
- Trauma
- Tear film problem (e.g. KCS)
- Adnexal conditions
- Primary corneal disease (e.g. SCCEDs)
- Infection
- Neuro disease
What might have caused these ulcers?
These ulcers occurred secondary to keratoconjuctivitis sicca
* These ulcers have a circular ‘punched out’ appearance and deteriorate rapidly
Entropion
Eyelid mass
Ectopic cilia
Pug with macropalpebral fissure resulting in lagophthalmos and exposed cornea
Shih tzu with triachiasis resulting from pronounced nasal fold
Spontaneous Chronic Corneal Epithelial Defects which can cause corneal ulceration
These are especially common in Boxers and are often un-healing.
Only epithelium is lost but it fails to adhere to underlying stroma - reason unknown.
Recurrence a common ssue.