Ferning in conjunctival-cytologic preparations. Crystallisation in stained semiquantitative pipette samples of conjunctival fluid.

Two quantitative pipette samples and 3 smears from each of 305 eyes were re-evaluated. Two types of ferning (F) were detected i.e. rectangular (FR) and acute-angled (FA) ramifications, respectively. One FR corresponds in area to 0.11 FA. Ferning was present in 29% of pipette samples, averaging 0.41 mm2 in the form of FR in the total series. Ferning was most frequent in samples with fairly large amounts of mucus, more frequent in neutrophilia than in lymphocytosis, and the rarest in normal cytology. F was seen in several cases of acute infections conjunctivitis (55%), neonatal and follicular conjunctivitis, and keratitis, whereas it was rare in normal eyes (7%). This distribution is presumably due to the amount of mucus in the samples preserving the F-pattern during the preparation procedure. F was rarely seen in smears (0.7%).