Cornea (M2) Flashcards
What are the layers of the cornea?
- epithelium
- Bowman’s layer
- Stroma
- Descemet’s membrane
- edothelium
What percentage of the corneal thickness is stroma?
90%
What percentage of the refractive power of the eye is due to the cornea?
75%
What is the average thickness of the cornea?
540 microns
How long does it take to heal the Bowman’s membrane?
6 weeks
What layer of the cornea holds mucin and keeps the cornea hydrated?
glycocalyx layer (Slime layer)
What hold the basal corneal cells together?
zonal occludens
What holds the basal corneal cells to the basement membrane?
hemidesmosomes
How many cells/mm does a normal adult endothelium have? 1. At what number of cells does edema occur? 2
- 3,000
2. 500 cells/mm
What are the gram positive bacteria that make up the normal flora of the cornea?
- Staph. aureus (common)
- Staph. epidermidis (common)
- Diphtheroids
- Propionibacterium acnes
- Strep. pneumonia
- Strep. viridans
What are the gram negative bacteria that make up the normal flora of the cornea?
- E. coli
- Klebsiella
- Proteus
- Moraxella
- Pseudomonas (rare)
- Haempjilus influenzae (rare)
What are the fungi that make up the normal flora of the cornea?
candida (less common)
What is the enzyme on the cornea that breaks down bacterial cell walls?
lysozymes
What is the metal chelating protein found on the cornea?
lactoferrin
What is the antibody the prevents bacterial adherence on the cornea?
IgA
What are the risk factors for microbial keratitis?
- CL wearer
- Trauma
- topical corticosteroids
- chronic corneal surface disease
- ocular surgery
- ocular adnexal conditions
- systemic disease
- smoking
What are the bacteria capable of corneal penetration without epithelial compromise?
- Neisseria gonorrhea
- Neisseria meningitidis
- Hemophilus influenzae
- Corynebacteria diphtheria
What is required for the infection to be an infectious corneal ulcer?
- eroded epithelium
2. underlying stromal infiltrate
What are the proper times to culture a kerititis?
- non-responsive lesion
- extensive infiltration of cornea
- lesion >1.0mm that is central or paracentral
- post-surgical infection
- monocular patient
- immunocompromised patient
What does the prescription abbreviation “ad lib.” mean?
freely, as needed
What does the prescription abbreviation “a.c.” mean?
before meals
What does the prescription abbreviation “b.i.d.” mean?
twice a day capsule
What does the prescription abbreviation “gtt.” mean?
drops
What does the prescription abbreviation “h.s.” mean?
at bedtime
What does the prescription abbreviation “p.c.” mean?
after meals
What does the prescription abbreviation “p.o.” mean?
by mouth
What does the prescription abbreviation “p.r.n.” mean?
as needed
What does the prescription abbreviation “oint” mean?
ointment
What does the prescription abbreviation “qAM” mean?
every morning
What does the prescription abbreviation “q.4.h.” mean?
every four hours
What does the prescription abbreviation “q.d.” mean?
daily
What does the prescription abbreviation “q.h.s.” mean?
at bedtime
What does the prescription abbreviation “q.i.d.” mean?
four times a day
What does the prescription abbreviation “q.o.d.” mean?
every other day
What does the prescription abbreviation “sol” mean?
solution
What does the prescription abbreviation “susp” mean?
suspension
What does the prescription abbreviation “t.i.d.” mean?
three times a day
What does the prescription abbreviation “top” mean?
topically
What does the prescription abbreviation “ung” mean?
ointment
What does the prescription abbreviation “Ut dict. or UD” mean?
as directed
How many days should you wait to apply a steroid when dealing with gram + bacteria? 1. Gram -? 2
- at least 2 days
2. at least 3 days
What is it called when fluid from the anterior chamber is coming through the cornea?
Positive Seidel sign
Where do HSV1 infections take place on the body? 1. HSV2? 2
- above the waist
2. below the waist
What are two methods for determining corneal sensitivity?
- corneal cotton tip wisp test
2. corneal anesthesiometer
What type of anti-viral medication used to treat HSV kills DNA non-specifically?
Trifluoridine
What type of anti-viral medication used to treat HSV kills DNA specifically?
Zirgan
What are the causes of pseudo-dendrites?
- Herpes Zoster
- healing corneal abrasions
- Acanthamoeba
- corneal epithelium graft injection
- Tyrosinemia type2
- CTL
- toxic Keatopathy as a result of topical meds
What were the major findings from the Herpetic Eye Disease Study I (HEDS I)?
- epi disease not make future recurrences more likely but stroma disease does
- stromal disease can occur w/o epi involvement
- Oral acyclovir dec reoccurrence
- steroids effective in managing stromal infections
- oral acyclovir beneficial in tx of HSV uveitis
What were the major findings from the Herpetic Eye Disease Study II (HEDS II)?
oral acyclovir reduce recurrence of any form of ocular herpes (epi and stromal)
What neurological palsies can be impacted by Herpes Zoster?
III, IV, or VI
What are the possible triggers of interstitial keratitis?
- syphilis
- TB
- HSV and HZV
- Sarcoid
- Cogan
What is lipid accumulation in the cornea called? 1. What is it secondary to? 2. What is a possible treatment? 3
- lipid keratopathy
- interstitial keratitis
- lasering of BV’s
What are the peripheral acting analgesics given to treat pain associated with keratitis?
- topical anesthetics
2. topical NSAIDs
What are the central acting analgesics given to treat pain associated with keratitis?
- Vicodin (A+H)
- Percocet (A+O)
- Tylenol 2 or 3 (A+C)
Which level of drug has the highest potential for abuse?
level I
What level of drug is vicodin and percocet?
level II
What are areas of corneal thinning as a result of poor wetting? 1. What is the treatment? 2
- Dellen
2. Aggressive corneal lubrication
What are the therapeutic uses of contact lenses?
- restoring optical clarity
- promoting epithelial healing
- pain relief
- preservation of corneal integrity
- future: drug delivery
What is a corneal side effect of the heart medication Amiodarone?
Corneal Verticillata (Vortex Keratopathy)
What is a corneal side effect of antidepressants, oral contraceptives, and anti-acne medications?
dry eye
What is it called when something that is purposefully put in the eye damages the eye?
corneal medicamentosa
What side effect in the cornea do older antiviral meds cause?
PEK
What side effect in the cornea do topical anesthesia meds cause?
Sloughing of epithelial cells
What side effect in the cornea does recreational drug use (meth and crack) cause?
epithelial sloughing