Abstract
Purpose: :
Impression cytology (IC) is now an accepted technique for collecting the most superficial layer of the conjunctival cells ((both goblet and non-goblet cells) for the analysis of ocular surface disorders. The type of filter paper (characterized by pore size and base material) and the technique of cell collection will affect the number and state of epithelial cells collected. Larger pore sizes collect cells better, but cell morphology is less well preserved. Presence of surfactant may also reduces cell pick up. Most authors suggest the use of filter paper of a pore size between 0.22 and 0.44 µm, but most filters present an asymetric structure. We also investigated the potential of a new device to collect cells from conjunctival epithelium. Number and state of collected cells were evaluated using different membrane materials.
Methods: :
Supero-temporal conjunctival epithelium of pigmented rabbits (3 per sample) was sampled using 69 sqmm filter membranes. Different materials (Millipore Mixed Cellulose ester - MCE - with and without surfactant, Pall and Millipore Polysulfone - PSU -, symmetric, asymmetric or oleophobic) were tested, Asymmetric membranes were tested both sides. All membranes have a pore size of 0.2µm. Rabbit were anesthetized for precise collection procedure without local anesthesia.Membrane were stained in PAS-Hematoxylin and cells counted at 3 locations per sample on a 170µmx133µm area using confocal microscopy.
Results: :
MCE membranes mean cell count was 118 (SD 120), MCE surfactant free membrane was 3 (SD 4). Cell counts for PSU membranes, smooth side Millipore TCMF, EIMF (high flow), Pall SUPOR were 7 (SD 8), 12 (SD 10), 282 (SD 340) respectively. Cell counts for PSU membranes, rough side Millipore TCMF and EIMF was impossible due to cell lysis. Cell count for Pall SUPOR on rough side was 543 (SD 254).Cell count for PALL SUPOR R (oleophobic) was 0 on both sides.
Conclusions: :
These results show membranes for IC cannot be characterized only by pore size. Membrane structure, asymetric surface and role of surfactant play a critical role for the number of cells collected. Choice of appropriate membrane characteristics together with a new collection device improves cell collection in IC and potential for exploitation.
Keywords: cytology • conjunctiva • flow cytometry