Diagnostic Stains Flashcards
Fluorescein sodium overview
- orange red dye fluoresces in high dilution
- used topically - also injected systemicallu for fluoroscein angiography
not a true stain - colours the tear film, tear film doesnt invade intact corneal epithelium
- lipid membrane impermeable to water
- epi damage means fluoroscein can gain access to deeeper layers
how does fluoroscein sodium work?
- light ~ 485-500nm absormed maximally (absorbs in blue range)
- this absorbed energy excited fluorescein molecules
- emits light between 525 and 530nm (emits in green range) - can use a wratten 12 filter to improve contrast
- burton lamp emits light 305 to 410nm - some rgp lenses absorb light bet 315-400nm
- blue filter on slit lamp
what is sodium fluoroscein used for
- assessment of corneal integrity - trauma, disease, CL aftercare
- rgp fitting
- contact tonometry
- TBUT
- lacrimal patency (open) - checkin drainage system is open
- lacrimal drainage
sodium fluoroscein contraindications and cautions
contraindications:
- known sensitivity
- SCLs
cautions (multi dose bottles)
- contamination problem in hosp in 1950s
- fluoroscein is used on damaged cornea
- pseudomonas has an affinity for fluoroscein - progresses rapidly, corneal perforation within 48 hrs
fluoroscein sodium preparations
Minims 1% and 2%
- orange yellow
- slightly alkaline
- contains buffer to stabilise solution
- may be combined with anaesthetic
fluoroscein impregnated strips - 1mg
store below 25 degrees celsius
what is rose bengal
- derivative of fluoroscein
- stains devitalised epi cells of cornea and conj. also stains mucus strands
- antiviral effect
- stings on insertion - esp in dry eyes, maybe use anaesthetic?, may also cause punctate staining, has toxic effect on human corneal epi cells, enhanced by light exposure
- has been available in 1% minims (not commercially available), and rose bengal opthalmic strips 1.3mg
conditions in which rose bengal is useful
- keratoconjunctivitis sicca
- dendritic keratitis
- neuroparalytic keratitis
- exopthalmos
- pressure areas due to CL wear
lissamine green
- opthalmic strips 1.5mg if dye
actions similar to rose bengal - stings less
- less toxic
- no antiviral effect
- like rose bengal, binds to nucelie of severely damaged cells
- staining effect lasts longer than rose bengal
how to observe lissamine green
- observe 1-4 mins after instillation
- too soon - staining pattern wont have developed, too late some of the pattern will have faded
- begin with low illumination, high illumination will bleach out the appearance of some of the staining
- can use red filter (wratten no 25)
- some evidence to suggest that early signs of DED more visible with lissamine green compared to fluoroscein
- like rose bengal, easier to view against lighter iris
other stains
alcian blue - stains mucus
trypan blue - mucus and dead cells which have undergone structural changes
bromothymol blue - degenerate and dead cells, mucus, used to investigate damage by chemical agents
methylene blue - bac stain that will also stain nerve tissue
tetrazolium and lodonitrotetrazolium - tetrazolium is used to stain degenerate cells (not living or dead), used for staining of tumours and assessing corneal grafts
