Dyes Flashcards
Characteristics of fluorescein
- Water soluble
- Weakly acidic anion in alkaline solution such as
tears - Maximum fluorescence at pH 8
- Commonly available as sodium salt (NaFL)
- Metabolised by liver
- Eliminated in urine
- Absorption spectrum in blood: 465 nm
- Absorption spectrum on ocular surface: 450-493 nm (blue)
produced through a Cobalt blue slit lamp filter - Emission 520 nm (yellow-green) isolated with a Kodak
Wratten barrier filter - Absorption/emission spectra are dependent on the absorption spectrum, pH and concentration of the fluor; fluorescence is best at [0.1%] vs negligible at [2%]; avoid excess application of fluorescein
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Fluorescein quenching phenomenon
Fluorescein formulations with standard molecular weight topical (376kD)
Fluorescein formulations with high molecular weight (topical) (710kD)
What % of circulating fluorescein is bound to serum proteins RBCs (inactive)
70-85%
Dose of IV or oral fluorescein
Indications of topical fluorescein
Corneal abrasion vs ulcer
How does fluorescein help with dry eye assesment
Fluorescein pools in gaps created on the ocular surface by lost
epithelial cells following exposure-mediated damage to tight-junctions
Diffuse punctate keratitis
Tear meniscus height
Rigid gas permeable (RGP) contact lens fit evaluation with topical fluorescein
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Jones I Test: Diagnosis of Tear Duct Obstruction
- Jones I: fluorescein is applied to ocular surface; an anesthetized cotton-tipped swab is inserted into the ipsilateral nostril for 5 min, then evaluated for staining
Jones II (Irrigation) Test
Diagnosis of Epithelial Keratitis