Diagnostic Stains Flashcards
(50 cards)
what type of light do diagnostic stains emit?
lower energy (longer wavelength) - molecule will absorb highest energy (shortest wavelength)
are diagnostic stains acidic or basic?
can be either but not neutral
Is fluorescein water or oil soluble? and where is it ionized?
water soluble and ionized in the tears (hydrophilic)
When will fluorescein be able to enter the cornea (lipophilic)?
cornea will be compromised (not intact) - dry eye, abrasion, ulcer, lesions - tight junctions are broken = corneal staining
what is absorption of fluorescein for tissue and blood?
excited by 493nm (cobalt blue) and 465nm in bloodstream
why does the blood need a higher energy to become excited?
binding in the blood to albumin and RBC’s reduces the activity
what is the emission of fluorescein?
520nm (yellow/green color is seen)
what color of fluorescein is seen on the tear film?
orange/yellow/green –> need to enhance with a wratten filter
what is seidel’s sign?
used to assess the presence of anterior chamber leakage through the cornea from a penetrating injury (will see fluorescent green in bowman’s membrane or aqueous humor)
what is quenching?
some atoms or molecules can facilitate non-radiative transitions to ground state (occurs without emitting photo - steals the energy)
which anesthetic causes the least amount of quenching? what about the most?
least = BAK + benoxinate middle = proparacine most = tetracaine
what happens to IOP readings with fluorescein quenching?
intensity is diminished - underestimation of IOP
how can fluorescein detect an ulcer?
penetration below basement membrane of corneal epithelium - exposes the stroma = dye will disperse 360 in eye
how can fluorescein detect an alkaline burn?
chemicals/molecules will precipitate by biding with a salt and deposit in the lower fornix - will stain will dye
how can fluorescein evaluate tear break-up time (TBUT)?
after complete blink - look for the first randomly distributed dark spot in tear film (interval = TBUT)
how can fluorescein be used to evaluate RGP CL adaptation?
anywhere you see dye it is trapped under the lens - not in absolute contact with the eye (need different lens if no dye is seen)
how do you use a Wratten filter when elvauating RGP fit?
filter is required over the light source
how can fluorescein be used to diagnose a tear duct obstruction/epiphora?
use with a Jones test
how is fluorescein used with aniline dye from indelible pencils?
it is an antidote - methyl violet spreads through ocular tissues and is precipitated by 2% sodium fluorescein
how can you measure aqueous humor production with fluorescein?
patient drinks dye –> goes into bloodstream and to the eye (watch appearance in anterior chamber)
how can fluorescein be used to distinguish between viral keratitis caused by herpes simplex or herpes zoster?
dye highlights the filaments
simplex = bulb-like ends
zoster = thin ends
How is fluorescein used in angiography?
used to visualize structural defects, vascular pathology, tumors, RPE thinning, CME, AMD (10-15 sec to arrive at retina)
After administering fluorescein to antecubital vein, what do you watch for on the fundus photos?
any areas of pooling in the macula = diabetes, AMD, Stargardt’s disease and tumors
What are HMW (high molecular weight) fluorescein formulations used for?
used with soft CL because they can stain with LMW - the HMW are too large to be absorbed by the lens
