Diagnostic stains Flashcards
Fluorescein sodium uses and disadvantages
Uses:
- Tonometry
-Corneal abrasions
- Contact lens fittings
Disadvantages:
- In multidose form can cause Pseudomonas and aeruginosa
Rose bengal uses and disadvantages
Uses:
- Staining of dead and devitalised i.e weak cells in the cornea and conjunctiva - aids dry eye diagnosis.
Disadvantages:
- Irritates dry eyes on instilation
- Stings.
- Can also stain healthy cells = hard to make diagnosis
Features of fluorescein sodium
- Orange-red dye fluoresces in high dilution
- P: For use and supply by all optometrists
- Used topically
- Also injected systemically for fluorescein
angiography - Not a true stain
* Colours the tear film
* Tear film does not invade intact corneal
epithelium in healthy cornea but will if break in epithelium
* Lipid membrane impermeable to water
* Epithelial damage means fluorescein can
gain access to deeper layers
How does fluorescein sodium work
- Blue filter on slit lamp emits light between 390 and 410nm = so useful to use to enhance contrast
- Light 485 to 500nm absorbed maximally (absorbs in blue range)
- This absorbed energy excites 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
Uses of fluorescein sodium
- Assessment of corneal integrity
– Trauma
– Disease
– Contactlensafter-care - Rigid contact lens fitting
- Contact tonometry
- TBUT
- Lacrimal patency ( is drainage system is open)
- Lacrimal drainage
Contraindications of fluorescein sodium
- Known sensitivity
- Absorbed by soft contact lenses
Cautions of fluorescein sodium multi dose bottles
- Contamination problem in hospitals in 1950s
- Fluorescein is used on damaged cornea
- Pseudomonas has an affinity for fluorescein
*Progresses rapidly
*Corneal perforation within 48 hours
= propagating pseudomonas keratitis = sight threatening consequences
How is fluorescein sodium available
- Minims 1 and 2%
– Orange-yellow
– Slightly alkaline
– Contains buffer to stabilise solution
– May be combined with anaesthetic = saves time - Fluorescein impregnated strips ~ 1mg
- Store below 25°C
Features and side effects of rose bengal
- Derivative of fluorescein i.e made from fluorescent
- Stains devitalised epithelial cells of cornea and
conjunctiva. - Also stains mucous strands
- Anti viral effect
- Stings on insertion
* Especially in dry eye conditions
* Use anaesthetic first? - May also cause punctate staining
- Has toxic effect on human corneal epithelial cells, enhanced by light exposure
How is rose bengal available
- 1% minims (not commercially available)
- Rose Bengal ophthalmic strips 1.3mg
Which conditions is it useful to use rose bengal
- Keratoconjuctivitis sicca
- Dendritic keratitis
- Neuroparalytic keratitis
- Exopthalmos
- Pressure areas due to contact lens wear
What is useful when using rose Bengal - which filter
Red-free (green) filter to enhance visibility
When is it easier to see rose bengal staining
Easier to view against light blue iris, less so with a darker iris
How is lissamine green available
Lissamine green ophthalmic strips = 1.5mg of dye
Features of lissamine green
- Actions similar to Rose bengal
- Stings less
- Less toxic
- No antiviral effects
- Like Rose bengal, binds to nuclei of severely damaged cells
- Staining effect lasts longer than Rose bengal
- Observe 1-4 minutes after instillation
■ Too soon-staining pattern won’t have developed. Too late-some of the pattern may fade
■ Begin with low illumination, high illumination will bleach out the appearance of some of the staining
