Nucleus and cell size changes in human bulbar conjunctival cells after soft contact lens wear, as assessed by impression cytology

Abstract 

Purpose

To specifically assess the nucleus size and its relationship to cell size for human bulbar conjunctival cells.

Methods

Impression cytology samples were taken from the nasal side of the intra-palpebral zone of the bulbar conjunctival surface from 20 young adult white European males, half of whom were successful daily soft contact lens wearers. A Millcell^®-CM filter was used, after topical anaesthesia with oxybuprocaine 0.4%, which was stained with Giemsa and colour images taken at 400× magnification by light microscopy. The images were graded and also a 35mm was prepared. From the projected image, an overlay method was used to outline the borders such that the cell and nucleus areas could be measured by planimetry.

Results

The group mean cell area values were 267±59μm² (n=10, ±S.D.) and 1028±357μm² for the non-contact lens wearers and contact lens wearers, respectively. The cell nucleus areas were 64±11μm² and 99±19μm², respectively. Both the cell areas and nucleus area values were statistically different between the two groups (p<0.001).

Conclusions

These studies confirm that soft contact lens wear can result in cell enlargement (squamous metaplasia) of the bulbar conjunctival cells. With this cell enlargement, the nucleus-to-cytoplasm ratio also changes, but the nucleus size generally increases (rather than decreases).

Keywords: Impression cytology, Bulbar conjunctiva, Human, Contact lens, Squamous metaplasia, Nucleus-to-cytoplasm ratio