Anesthetics & Dyes Flashcards
1 dye in clinic
Fluorescein sodium
Fluorescein sodium absorbs __ and emits ____.
Absorbs blue (493nm) and emits green (520nm)
Clinical uses of fluorescein sodium
Topical & oral & intravenous
Fluorescein sodium is used topically for
Evaluating ocular surface integrity, tear film visualization and analysis, CL fitting, lacrimal drainage evaluation , and Goldmann
Optics of fluorescein angiography
Only blue light is allowed through the excitation filter
Only green light is allowed to pass through the barrier filter
Fluorescein injection have rare cases of death due to
Anaphylaxis
Fluorescein can be consumed orally to perform
Angiography
Factors affecting intensity of fluorescence
- concentration
- pH
- wavelength of the exciting light
- thickness of the layer of fluorescein
- presence of substances that suppress fluorescence (quenching)
Decreased fluorescence at high concentrations is due to
Quenching
Intensity of fluorescein sodium increases with (concentration)
Increasing concentration up to 0.001% , above which it diminishes
Intensity of fluorescein sodium increases with (pH)
Rising pH until pH 8 after which there is a decrease
Intensity of fluorescein sodium increases with (wavelength)
Peak emission from fluorescein is achieved with exciting light of 493 nm
Intensity of fluorescein sodium increases with (thickness of the layer)
Increases linearly up to a point with the thickness of the fluorescein solution
Intensity of fluorescein sodium is suppressed by
Topical anesthetics and other drugs
Other fluorescein molecules when at high concentration (self quenching)
How does hyper fluorescence happen on the ocular surface
- fluorescein pooling
- ingress around cells
- uptake by damaged cells
Ingress of fluorescein sodium around cells is caused by
Disruption of tight junctions at the epithelial surface
Higher pH of intraepithelial environment may contribute to
Greater fluorescence
Fluorescein may enter and become concentrate within damaged epithelial cells, but it
Does not stain/bind
Increased concentration of fluorescence within damaged cells my contribute to
Greater fluoresce
Fluorescein can enter the epithelium only where
There is interrupted continuity of the epithelial surface / damaged epithelium
Fluorescein penetrates
Intercellular spaces and concentrates inside damaged cells
What does fluorescein bind to during staining
NOTHING
Staining is transient
What is the dye of choice for evaluation of corneal surface integrity
Fluorescein sodium
Filter used to excite fluorescein sodium dye
Cobalt blue filter making lesions appear vivid green
Filter for fluorescein sodium enhances visualization of stained areas
Yellow barrier filter
What to do if fluorescein doesn’t stain after the 1st instillation
Apply every 3-5 min over a 30 min interval for a total of 6-10 instillations
Clinical significance of fluorescein reveal after sequential instillation
Associated with cl intolerance
Seidel sign
Flow of aqueous through a defect in the globe visualized with the use of fluorescein
Aqueous could come from anterior chamber
Fluorescein no wetting /negative staying
Absence of tears on the corneal surface appear as dark regions of non fluorescence
How is fluorescein sodium used for CL fitting
Rigid lens alignment with corneal surface
Hypofluorescence in areas of greater contact
High molecular weight fluorescein maybe be used in conjunction with
Soft contact lenses to prevent penetration of the dye into the lens matrix
Fluorescein sodium used in lacrimal system evaluation
TBUT
Jones test
TBUT with fluorescein sodium
The time interval between the last complete blink and the first randomly distributes dark spot (nonwetting) in the tear film
TBUT indication of dry eye
Decreased break up time
Jones test with fluorescein sodium measures
Patency of the lacrimal drainage system
How is jones test performed
Evaluated by instilling NaFl into the eye and then observing for its presence in the nose
Jones test is useful in evaluating symptoms of
Wet eye
Norm for TBUT
10 seconds
6-10 is moderate
5 is severe
Applanation Tonometry
Fluorescein permits visualization of the applanated area
What if applanation Tonometry is done with out fluorescein?
It will underestimate IOP because of decreased visibility of the apex of the tear meniscus
Topical adverse reactions of fluorescein sodium
Mild transient stinging
Systemic adverse reaction of fluorescein sodium
Rare cases of anaphylaxis that may be fatal
Fluorescein sodium is highly susceptible to
Bacterial contamination
Especially pseudomonas aeruginosa
An iodine derivative of fluorescein
Rose bengal
Rose Bengal binds to/ stains
- mucus in the tear film
- epithelium with disturbed glycocalyx
- devitalized (dead tissue)
Is Rose bengal a vital dye?
No
Rose bengal is photoreactive and generates
Singlet oxygen when exposed to light which is highly toxic got cells
Rose bengal will instantly kill and stain
Unprotected cells exposed to it
A cotton candy like structure that the epithelial surface binds mucin onto the ocular surface
Glycocalyx
Toxicity of rose bengal can be blocked by an
Intact glycocalyx
What’s a vital dye?
A non toxic dye that satins devitalized tissue
Used to determine live/dead cell ratio
Why is rose bengal not a vital dye?
It’s toxic and will kill live healthy cells if there is a compromised glycocalyx
Rose bengal is best performed by
Using 1% sol.
Waiting a few min. before examination with both white and red free light
If you instill rose bengal and then fluorescein
Subtle areas will be highlighted by surrounding flourescein and use of blue light
Dye of choice for assessment of conjunctival staining
Rose bengal
Temporal conjunctival rose bengal staining differentiates
Sjorgren syndrome from KCS
Clinical uses of rose bengal (3)
- dry eye syndrome
- H. Simplex dendritic ulcers
- H. Zoster pseudodendrites
Swollen epithelial cells that stain minimally with fluorescein and vividly with rose bengal
H zoster pseudodendrites
Stains with flourescein along length of lesion, but the raised edges stain negatively
H simplex dendritic ulcers
Rose bengal is taken up by the swollen epithelial cells at the ulcers border and terminal bulbs
H. Simplex dendritic ulcers
Contraindication of rose bengal
Toxic to H. Simplex
Don’t use prior to culturing suspected hermetic lesions
Side effects to rose bengal;
Stains skin/clothes
Burns
Stains in an identical fashion to rose bengal
Lisasmine green
Is lissamine green a vital dye ?
Yes
Stains membrane damages or devitalized cells
Topical anesthetic MOA
Prevents generation and conduction of nerve impulses
Efficacy of topical anesthetics is determined by
Their ability to suppress corneal sensitivity
What happens if you combine two or more topical anesthetics
Does NOT produce an additive effect, but does increase the risk of side effects
All topical anesthetics are
Esters
Amide anesthetics are
Less toxic
Ocular toxicity of topical anesthetics
Desquamation of corneal epithelium
Retards epithelial mitosis and migration
Inhibits epithelial mitosis and migration
Mild stinging
Diffuse SPK may occur following a single drop of topical anesthetic due to
Corneal toxicity
Local hypersensitivity reactions of topical anesthetics
- Allergy can develop die to repeat exposure (glaucoma pts)
- mild blepharoconjunctivitis
- little cross reactivity among topical anesthetics
How to treat blepharoconjunctivitis
Cold compresses and topical decongestants
Systemic hypersensitivity reactions to topical anesthetics
No life threatening reactions reported
Self administration of topical anesthetics
- adverse effects due to corneal toxicity
- permanent vision loss due to corneal scarring
- health care workers have access to them
Dispensing of topical anesthetics to patients
NEVER DISPENSE
When to consider topical anesthetic abuse
Differential diagnosis of unexplained chronic persistent corneal erosions
Clinical features of anesthetic abuse
- intense pain, severe tearing, photophobia
- There is a vicious cycle of pain, leading to more frequent use of drops, causing motor damage and pain
- epithelial defect
- ring shape opacification
- stroma infiltrate
- hypopyon
- contact dermatitis
Most of the patients abusing anesthetics had
Epithelial defects
Topical anesthetics use for short term under close supervision is highly controversial
Alternative methods are equally effective, less toxic and less prone to abuse
Pregnancy contraindications of topical anesthetics
All are pregnancy category C
Cross sensitivity between topical anesthetics
Substitute different topical anesthetics because there is little cross sensitivity
topical anesthetics for dry eye testing
Do not instill a topical anesthetic prior to checking for ocular surface disease
Epithelial toxicity can confuse clinical picture
Instillation of a topical anesthetic prior to obtaining a culture specimen may
Decrease yield because anesthetics are toxic to microorganisms
Which topical anesthetic is the least toxic
Proparacaine
Topical anesthetics precaution during pachymetry
May cause transient corneal swelling
Wait 5 min after instillation prior to performing pachymetry for accurate measurements
Topical anesthetics could cause perforating injuries
Endothelial toxicity if anesthetic enters AC
Commonly used anesthetics
Proparacaine
Tetracaoine
Benoxinate
Potency among the topical anesthetics proparacaine tetracaine and benoxinate
No significant difference in potency
Benoxinate is only availed
As 0.4% soln combined with flourescein for Tonometry
Benoxinate contraindications
Same as all topical anesthetics
Benoxinate side effects
Mild stinging
Epithelial desquamation (less than proparacaine)
Little cross sensitivity with tetracaine or proparacaine
Advantage of benoxinate
Less desquamation
Benoxinate during applanation Tonometry
Rapid onset and brief duration
Minimal quenching of fluorescein
Good comfort
Quenching
Process that to a reduction in fluorescence
Proparacaine is commercially available in
0.5% solution
What if proparacaine looks a faint yellow ?
Don’t use
It should be stored tightly, opaque and refrigerated container or retard degradation
Proparacaine has extremely low systemic toxicity
Poor penetration of the conjunctiva and cornea
Least bacteriocidal of the topical anesthetics and should be used prior to obtaining cultures
Proparacaine
Least painful anesthetic
Proparacaine
Proparacaine quenching of fluorescein
Greater than benoxinate
Corneal toxicity of proparacaine
Low
Greater than benoxinate less than tetracaine
Contraindication of proparacaine
Same as all anesthetics
Typical allergic reaction of proparacaine
Contact beloharoconjunctivitis, consisting of conjunctival hypermedia, swelling of the eyelids, lacrimation and itching
