Comparison of Morphology of Bulbar Conjunctival Cells Assessed by Impression Cytology versus Scrape and Smear Methods

Abstract

Differences in cell and nucleus size can result from use of different processing methods. Therefore, in making comparisons between sets of conjunctival cells, it is important that cell collection and processing methods be considered.

Assessment of size and nucleo‐cytoplasmic characteristics of the squamous cells of the corneal epithelium

“…Impression cytological samples of this surface in ovine eyes revealed the morphology of these cells to also show distinct squamous characteristics with the cells being large, having large nuclei and a ‘low’ nucleo‐cytoplasmic ratio. For ovine inter‐palpebral bulbar conjunctiva, the cells are small, have smaller nuclei and a ‘high’ nucleo‐cytoplasmic ratio . Based on numerous assessments, the ocular surface of the ovine eyes used for the present studies does not routinely stain with either rose Bengal or lissamine green, indicating a normal healthy ocular surface.…”

“…The material for the present studies was from recent post‐mortem sheep eyes obtained from a local slaughterhouse by special arrangements . The eyes were earlier washed in cold tap water and, over a five‐year period, small batches of eyes (usually 10 to 15) in closed containers were received at the laboratory within two hours post‐mortem.…”

“…Corneal impression cytology was then undertaken using a 10 mm diameter Biopore® filter as available in a Millicell®‐CM unit 0.4 PICM 012550 (Millipore, Co. Cork, Ireland) essentially following previous protocols developed for conjunctiva . One side of the filter unit was marked with a vertical line to facilitate placement and serve as a reference for the horizontal meridian, the filter orientation and location with respect to the limbus, so to avoid any chance of peripheral epithelium being assessed.…”

Corneal Surface and Superficial Cells as Viewed by Scanning Electron Microscopy and Impression Cytology Sampling

“…Sheep eyes, within an hour of slaughter, were obtained from a local slaughterhouse, 34,35 which were collected in closed plastic bags after being washed in cold tap water. Single eyes were selected from any particular batch based on quality (ie, no signs of corneal edema or mechanical damage) and age (based on a horizontal corneal diameter of at least 22 mm); for the 18 eyes studied, these diameters were between 22 and 23.5 mm.…”

“…34,35 As with preparation for SEM, the surface was irrigated with 1% saline, and then left for 5 minutes to air dry at room temperature before IC. An IC specimen was taken using a 10-mm-diameter Biopore filter (Millicell-CM unit 0.4 PICM 012550; Millipore, Co, Cork, Ireland), fixed with the same glutaraldehyde solution used for SEM and stained with Giemsa.…”