Lecture 3: 11/16 Flashcards
to view corneal abrasions, you use a:
slit lamp
what chemical compound do you use during slit lamp exams
sodium flurosine
some other qualities of slit lamp
magnified view and has a dark blue filter
corneal abrasions usually heal in
24-48 hours
2 step process in healing of corneal epithelium
- migration of cells on either side of the abrasion to the hole or scratch
- rapid mitosis, basal cells undergoing mitosis to make new cells that eventually make it to the surface
what is different about healing of a large abrasion area
primary means of repair is mitosis, and it can take about a week for the cells to regenerate and then migrate up to surface
there is no scar tissue after healing of damage if on what layer of the cornea
epithelium
there is scar tissue after healing of damage on what layers of the cornea
stroma and bowman’s
what can occur with an abrasion from organic matter?
recurrent corneal erosion
what is a recurrent corneal erosion and what does it cause?
it interferes with basal cells sticking on to basal membranes (hemi-desmosomes) and corneal abrasions will recurrently “rip off” the cornea
3 examples of treatment options for recurrent corneal erosions
- hypertonic drops
- topical steroids and tetracycline
- fibronectin
what does fibronectin do
wound healing agent, aids in migration of the cells
how common are WBCs in the epithelium?
rare
what are infiltrates?
when a large number of macrophages go to site of infection and form white spots on the cornea
if WBCs and infiltrates are found in the epithelium, in which layer would they be in?
basal layer
appearance of the basement membrane under electron microscopy is
a thin black line
will the basement membrane heal with or without scar tissue?
without
but it is so thin it is hard not to also damage the layers underneath it
what type of tissue is the basement membrane made of?
a condensation of fine fibrils of connective tissue
how thick is bowman’s membrane?
12 microns
structure of bowman’s membrane
modified connective tissue
homogeneous
the border of bowman’s against the _____ membrane is distinct
basement
anterior
the border of bowman’s against the ______ membrane is not as distinct
stroma
posterior border
in bowman’s membrane, pores are found and serve what purpose
for the nerves to pass towards the basal cornea
what is special about the repair of bowman’s
it doesn’t regenerate as original tissue, it regenerates as fibrous tissue if damaged (Scar)
the stroma accounts for ___ % of the corneal thickness
90%
how thick is the stroma in microns
500 microns
edema in the cornea is caused by
swelling of the cornea from the stroma taking up water
histology of stroma is
dense regular connective tissue
compact with lots of fibers and few cells
histochemically the stroma contains what substances in what percentages
78% water
15% collagen
4.5% micropolysaccarides
what types of fibers are in the stroma
collagen
what types of cells are found in the stroma?
a type of fibroblast called karatocytes that are modified and flat in the cornea
why is it good that the stroma has lots more collagen fibers than cells?
it doesn’t present a problem for transparency
total number of lamella and layer thickness in the stroma collagen fiber arrangement
200-250
thickness of 2 microns
bands of collagen fibers parallel have a width of
10-20 microns
run from limbus to limbus
MPS fiber percentages for sclera and stroma
sclera 1.5%
stroma 4.5%
effect of edema on stroma is
disrupt spacins
describe descement’s membrane layer composition
several layers of compressed filaments of collagen
thickness of descemet’s membrane at birth versus an adult
birth: 3 microns
adult: 12-20 microns
Descemet’s membrane serves as basement membrane for
endothelium
why is Descemet’s membrane tough to penetrate?
no elastic fibers
