Objective assessment of conjunctival squamous metaplasia by measures of cell and nucleus dimensions

The main aim of this work is to present a special method for conjunctival impression cytology (CIC) and objective measures of measure cell and nucleus dimensions. CIC using Millicell® Biopore filters was obtained from 50 Caucasian adults from the nasal bulbar conjunctiva. Giemsa-stained images of cells in a monolayer were photographed with a scale bar and projected at 1,500× to generate an overlay. Measures were made of both the long (L) and short (S) dimensions of the cells and the longest dimension of the nucleus (LN). The selected images comprised sets of 10 from different individuals, which had been assigned grades 0, 1, 2, or 3 and an additional grade 0.5. L ranged from 18.4 to 65.2 μm, S from 13.1 to 47.1 μm, to give average cell shape values (L:S ratio) of between 1.259 and 1.890. L and S were smallest for grade 0 cells (group mean 19.8 ± 1.1 and 14.8 ± 1.2 μm) and largest for grade 3 cells (group 51.2 ± 7.2 and 37.2 ± 4.7 μm), with no difference in L:S ratios across the cell grades. Longest dimension of the nucleus (NL) values ranged from 8.7 to 14.5 μm, with group mean values of 9.8 ± 0.6 μm for grade 0 cells and 12.9 ± 1.2 μm for grade 3 cells. NL was nonlinearly associated with L. Measures of conjunctival cell and nucleus dimensions can be used to objectively distinguish between cells assigned different grades of squamous metaplasia, with slight nucleus enlargement being the earliest detectable change (at grade 0.5).