CORNEAL STAINS

Fluorescein Stain

Taken up in areas with disruptions of cell-cell junctions or complete loss of epithelium
Hence identifies - corneal epithelial defects - abrasion or ulcer
Emits green (520 nm) on exposure to blue range light (490 nm - Cobalt Blue filter)
Can have characteristics
True Staining -
Pooling - a collection of fluorescein dye in depressions on the ocular surface but tissue does not stain due to intact epithelium - e.g. dallen
Negative staining - a collection of fluorescein dye around an elevated lesion
Seidel test - dilution of fluorescein from the ocular surface due to leakage of aqueous humor from a corneal perforation wound

Rose Bengal Stain

Corneo-toxic in vitro but considered safe in clinical use due to lower concentration
Stains devitalized epithelial cells even when epithelium remains intact
Irritant on use clinically hence requires Topical Anesthetic medication like proparacaine eye drops

Lissamine Green Stain

Useful to assess conjunctival epithelial integrity
Limited utility in corneal diseases due to dark background provided from the iris behind the cornea during slit lamp examination
Highlights damaged or absent corneal/conjunctival epithelium

Fluorescein Stain Rose Bengal Stain

Lissamine stain

Comparison of vital stains

Comparisons of dyes, information combined from Alves et al,6, Efron,4 Doughty et al,7 and Kim8 and Chodosh et al9

Staining of Corneal Dystrophies

Lattice Dystrophy – Apple green birefringence
Granular dystrophy- Masson trichrome
Macular Dystrophy- Alcian blue

Ref:

Smolin and Thoft's The Cornea - Scientific Foundations and Clinical Practice, Foster, Azar, Dohlman, Lippincott Williams & Wilkins, 4th edition, 2005, Section II - Examination and Evaluation Techniques, Chapter 6 - Slit Lamp Biomicroscopy and Photography, page 155-156.

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Cornea

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