Induction of conjunctival epithelial alterations by contact lens wearing. A prospective study

In a prospective clinical study, contact lenses were applied to 14 wearers of glasses with clinically and cytologically normal conjunctiva. The alterations of conjunctival cytology after the start of contact lens wearing were recorded with the technique of impression cytology over a period of 6 months. Within the first few weeks after application of the contact lenses, the patients developed a rapidly increasing alteration of cell size and nuclear morphology. Enlargement of the cell diameter with flattening of the cell body was seen together with numerous different nuclear alterations, in particular snakes (condensations of the nuclear chromatin into a sticklike or snakelike shape, centrally arranged in the nucleus). After this very rapid onset, the alterations increased more slowly towards a possible saturation point (and it seemed that the ultimate changes might possibly not be reached within the investigated period). At about 3-6 months, the patients reached a degree of cytological alteration which was seen in long-time contact lens wearers in our previous study and before this, except for the lack of keratinization, only observed in diseases of the ocular surface. There was a distinct squamous metaplasia of major parts of the conjunctival epithelium which normally is columnar and a decrease of goblet cell density. Squamous metaplasia and nuclear alterations increased with the length of time which had elapsed since the application of contact lenses and with extending the daily wearing time but were always restricted to the contact lens excursion zone on the eye and disappeared after contact lens omission, as seen before. Even patients with major cytological alterations remained free of symptoms, and the conjunctiva was still clinically normal.