title: Fluorescein punctate staining traced to superficial corneal epithelial cells by impression cytology and confocal microscopy.
abstract: OBJECTIVE
  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. In this study, the hypothesis that punctate erosions are individual cells with enhanced fluorescence was tested.
  
  
  METHODS
  Ten impression cytology membrane materials were compared, to optimize cellular yield in buccal mucosa and cornea. Clinicocytologic correlation of punctate fluorescent spots was performed in four dry eye patients. Individual punctate spots were localized by fiducial marks in photographs, before and after removal with impression membranes, and were traced in fluorescence microscopy and cytologic staining. Two-way contingency table analysis was used to determine the correlation of punctate spots with cells removed by the membrane. Clinicopathologic correlation of punctate spots was performed in 10 corneas removed in dry eye patients by transplantation for concurrent diseases. Punctate fluorescence was tracked in specimens by fiducial marks and epifluorescence. The distribution of fluorescent spots in specific cell layers of the cornea was determined by confocal microscopy.
  
  
  RESULTS
  Cellular yield was greatest with impressions from polytetrafluoroethylene (PTFE [Teflon]; BioPore; Millipore, Billerica, MA) membrane compared with its closest rival (P = 0.019). Punctate fluorescent spots, most of which disappeared after impression cytology (71%), correlated with cells on the membranes (P = 0.009). The punctate spots were more frequent in the superficial cell layers of the cornea (80%) compared with the deepest two layers (0%) (P < 0.00049).
  
  
  CONCLUSIONS
  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).
authors.affiliation: Jules Stein Eye Institute, Los Angeles, California, USA.
authors.forename: Maryam
authors.initials: M
authors.lastname: Mokhtarzadeh
authors.forename: Richard
authors.initials: R
authors.lastname: Casey
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Glasgow
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003584:Cytological Techniques; D015352:Dry Eye Syndromes / Q000175:diagnosis* / Q000378:metabolism; D019573:Epithelium, Corneal / Q000378:metabolism / Q000473:pathology*; D005141:Eyelid Diseases / Q000175:diagnosis* / Q000378:metabolism; D005260:Female; D019793:Fluorescein; D005456:Fluorescent Dyes; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D009061:Mouth Mucosa / Q000166:cytology; D011446:Prospective Studies; D013194:Staining and Labeling
chemical_list: D005456:Fluorescent Dyes; D019793:Fluorescein