Conjunctival cytology in asymptomatic wearers of soft contact lenses.

Conjunctival epithelium was systematically investigated with impression cytology in clinically asymptomatic wearers of soft contact lenses who had been using their lenses for several years. Severe abnormalities were observed, which had so far only been seen in diseases of the ocular surface mainly in dry eye syndromes. All patients showed evidence of squamous metaplasia with distinctly enlarged, flattened cells without evidence of keratinization. They also showed frequent nuclear abnormalities, primarily a high percentage of snakelike-appearing condensations of nuclear chromatin (snakes). The goblet cell density observed was relatively low. Snakes were for the first time detected outside the known localization (upper bulbar conjunctiva, 12 o'clock position) and could be demonstrated throughout the whole bulbar conjunctival epithelium. It is suggested that the changes observed are due to chronic mechanical irritation by the contact lens, as indicated by their topographical distribution and as proven by their reversibility after omission of contact lens wear.