Cornea Flashcards
corneal anatomy
1) outermost epithelium
2) stroma (mostly collagen-90% of thickness)
3) descement’s membrane (thickens with age)
4) innermost endothelium (monolayer, the pump)
cornea functions
- anterior structure for globe
- protection
- clear medium for vision
- REFRACTION
3 reasons why the cornea is clear
1) avascular
2) anhydrous
3) regular collagen arrangement
what can cause corneal opacification
- cellular infiltrate (infection)
- fibrosis (irregular collagen after injury)
- pigment (2nd to chronic irritation)
- neovascularization (source of edema; superficial = tree, deep = forest)
- edema
- mineralization/ lipid deposition (mostly underneath epithelium)
what is the most common presenting ophthalmic condition
corneal ulcers
what are the 3 things that treatment of corneal ulcers depend on
1) depth (superficial, stromal, descemetocele, full thickness/ iris prolapse)
2) etiology (trauma, infection, immune mediated)
3) response to therapy (simple, complicated)
_____ is the only structure lost in superficial corneal ulcers
epithelium
how does the corneal epithelium respond to injury
- mitosis stops
- cells at wound edge enlarge, lose attachment and migrate to injury (0.6mm/day if not infected)
- initial monolayer of cells cover injury, eventually will grow
- mitosis resumes after wound closure
- takes 6 weeks for BM to attach to stroma
- epithelium increases form 8 to 15 cell layers after injury
how does the stroma respond to injury
- re synthesis and cross linking of collagen
- balance of resorptive remodeling and restorative repair by fibroblasts
- PMNs get rid of necrotic tissue
- vessels aid healing, when done they collapse but “ghost vessels” remain
- corneal blood vessels move at ___mm/day
- WBC move in the cornea at ____mm/day
- epithelial cells move ___mm/day
- 1mm/day
- 8.6mm/day
- 1mm/day
dermoids
- normal tissue in abnormal location
- congenital
2 rules for ulcers
- treat aggressively
- recheck often
clinical signs for corneal ulcers
- blepharospasm
- epiphora
- serous to mucopurulent discharge
- miosis
- edema
- corneal vascularization
diagnostics of corneal ulcer
- culture if suggestive of infection
- STT
- fluorescein stain EVERY eye that shows pain
- cytology (horses)
descemetocele ulcer
- epithelium and stroma are 100% lost and DM is the only thing left
- DM will bulge due to pressure from AqH
- when staining, the only thing that will stain is the stroma so it will stick to the sides of the ulcer
iris prolapse ulcer
- DM has ruptured leaving a hole in the cornea open to the outside
- vision is lost
- iris passively follows AqH and plugs hole
melting ulcer
- proteases are active
- need to distinguish from corneal edema
- action of proteases is potentiated by topical steroids !!!!!!!!!
what is contained in tear film that is produced by inflammatory cells, epithelial cells, and fibroblasts that can prolong corneal healing in mild cases of imbalance ?
MMPs
Serine Proteases
3 bacteria + 3 fungi + 1 virus that commonly cause infectious ulcers
bacteria: pseudomonas, strep, staph
fungi: aspergillus, candida, fusarium
virus: herpes
goals of therapy for corneal ulcers
- sterilize wound bed
- control 2nd uveitis
- slow collagen breakdown
- provide structural support (cone of shame)
_____ is found in serum and can aid in reducing tear protease activity
alpha 2 macroglobulin with anticollagenase activity
-serum is: good for 8days; also contains nutrients that promote healing
reflex uveitis (not even really sure what this its... what does the "reflex" mean?)
all ulcers are associated with some iridocyclitis
-give atropine and systemic NSAIDs
True / false
topical corticosteroids are contraindicated in the face of corneal ulceration
TRUE !!!!!
-but can use topical NSAIDs if uveitis is the main problem… but be safe and stick to systemic NSAIDs
true / false
antibiotics are not toxic to epithelial cells
false ! they are !
