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Abstract: Testing fluorescein punctate staining

Fluorescein Punctate Staining Traced to Superficial Corneal Epithelial Cells by Impression Cytology and Confocal Microscopy.

The basis of fluorescein associated superficial punctate staining in dry eyes is controversial. Prior explanations include fluorescein pooling in surface erosive defects, intercellular trapping of fluorescein, and intracellular staining in dead cells. The hypothesis that punctate "erosions" are individual cells with enhanced fluorescence is tested.

Ten impression cytology membrane materials were compared to optimize cellular yield in buccal mucosa and cornea. Clinical-cytologic correlation of punctate fluorescent spots was performed in four dry eye patients. Individual punctate spots were localized by fiducials in photographs before and after removal with impression membranes and traced in fluorescence microscopy and cytologic stains. Punctate spots were correlated with cells removed by the membrane using two way contingency table analysis. Clinico-pathologic correlation of punctate spots was performed in ten corneas removed in dry eye patients receiving transplants for concurrent diseases. Punctate fluorescence was tracked in specimens by fiducials, and epifluorescence. The distribution of fluorescent spots in specific cell layers of the cornea was determined by confocal microscopy.

Cellular yield was greatest with impressions from polytetrafluoroethylene (PTFE, Teflon, Biopore) membrane compared to its closest rival (p=0.019). Punctate fluorescent spots that disappeared after impression cytology (71%) correlated to cells on membranes (p=0.009). The punctate spots were more frequent in the superficial cell layers of the cornea (80%) compared to the deepest 2 layers (0%) (p<0.00049).

Punctate epithelial "erosions" correspond to enhanced fluorescence in epithelial cells predominantly in superficial layers of the cornea and would be more aptly named fluorescent epithelial cells (FLECs).

Invest Ophthalmol Vis Sci. 2011 Jan 6. [Epub ahead of print]
Mokhtarzadeh M, Casey R, Glasgow BJ.
Jules Stein Eye Institute.