Lecture 4: 11/17 Flashcards
2 barrier types presented by the cornea are
lipid and water barriers
lipid barrier is found in the cell membranes of what 2 corneal layers
- epithelium
- endothelium
water barrier is found in what corneal layer
stroma (78% water)
keratitis means
inflammation of the cornea
common symptoms of keratitis
pain, photophobia, lacrimation, injection
photokeratitis is caused by
overexposure to UV radiation “sunburn of corneal epithelium”
common symptoms of photokeratitis
pain or “sandy” feeling, photophobia, lacrimation, and may have blepharospasm (hurts so bad they can’t open eyes)
treatment of photokeratitis
will treat itself, painkiller, maybe artificial tears, and follow up to make sure it isn’t infected
neovascularization of the cornea is when
there is growth of vessels on to the cornea
causes of neovascularization of the cornea
inflammation, irritation, or infection or tight fitting contact lenses
why is avoiding neovascularization of the cornea important
for contact lens patients and to reduce the possibility of a corneal graft being needed and rejection
what is the limbus?
transition zone between transparent cornea and opaque sclera
width of limbus
1.5-2.0 mm wide
appearance of limbus and edges
foggy, corneal side is more distinct than the scleral side
what are the interdigitations of the limbus
looks like fingers radially around the edge of the cornea and limbus
interdigitations of the limbus are called
palisades of Vogt
interdigitation upthrusts between waves in the epithelium are called
stromal papilla
what is unique about the epithelium between papilla
it is thicker and has a little bit of pigment in it, so it is a little darker
list of the 4 definitions of the limbus
- pathologists
- histologists
- anatomical
- surgical
(1) pathologist’s definition of the limbus
- anterior limit: the line from end of bowman’s to end of descemet’s
- posterior limit: 1.5mm posterior, perpendicular to surface (Everything between those limits is the limits)
(2) histologist’s definition of the limbus
- interface between cornea and sclera
- junction that starts at the end of bowman’s and is concave line that curves and comes back to the end of descemet’s
(3) anatomical definition of the limbus
- anterior limit: the end of bowman’s (corneolimbal junction)
- posterior limit: limboscleral junction
anatomical definition of limbus width of anterior and posterior limits
- anterior limit has elliptical shape and is 11.7 mm across
- posterior limit is 1.5mm horizontal and 2.0mm vertical
(4) surgical definition of the limbus
peel off (Reflected) conjunctiva, and it is the bluefish zone starting at the edge of the cornea into the sclera
both the corneal epithelium and the ____ is stratified epithelium
conjunctiva
what 3 corneal layers stop at the limbus?
bowman’s, descement’s, and endothelium
what 2 layers of the cornea continue at the limbus
epithelium and stroma
epithelium of the cornea becomes the ______ of the conjunctiva
epithelium of the conjunctiva
stroma of the cornea becomes what at the limbus
the sclera
what are some epithelium changes from cornea to limbus
epithelium of the cornea is smooth and flat, but epithelium of the conjunctiva is bumpy and irregular
function of the conjunctiva
protection, so keep bad stuff from getting behind the eye in the orbit, secretion
epithelium of the conjunctiva has how many layers?
10-15 layers
layers of the epithelium in cornea vs. conjunctiva
in cornea: 5-6 layers
in conjunctiva: 10-15 layers
3 types of cells found in the limbus
- fibroblast
- mast cell
- white blood cells (WBCs)
what is release from mast cells and why
histamine is released in large quantities when you get an allergic reaction
what is a mast cell stabilizer?
it stabilizes the cell membrane so it doesn’t break down and release histamine when you have an allergic reaction
(take about a month or 2 before episode to work)
sensory nerves that run into the cornea are derived from what nerve?
5th cranial nerve (V)
trigeminal
