Individual responsiveness to topical pilocarpine and the effects of variations in application technique.

The effects of nasolacrimal obstruction (NLO) and of eyelid closure (EC) were studied in a group of 6 healthy female subject (25-29 years). The aim was to determine the best application technique for patients. NLO or EC for 1 min was assumed to be a maximum time for patient compliance. A standard eye drop bottle was used with a drop volume of about 40 microliter. One drop of a 1% pilocarpine solution was instilled into the lower conjunctival sac of one eye in a randomized manner: a) NLO b) EC c) NLO and EC d) neither NLO nor EC. The effects on the pupil size, static refraction for distance and accommodative power were followed for 2 h. The results showed no significant difference between the 4 techniques. Pronounced interindividual differences but only small intraindividual differences were found in this group of healthy young females. Two subjects always responded strongly, and 2 other subjects always did so weakly. The application of the same amount of pilocarpine ointment (3%) increased and prolonged the effects on pupil size, refraction and accommodation at all points of time without reaching statistical significance compared with eye drops. Pilocarpine ointment caused considerable subjective discomfort. The experiments with pilocarpine suggest that, from a practical point of view, different techniques of application of ocular drugs seem to be a little importance with regard to local effect. The possibility of pronounced individual differences in pharmacological response should be borne in mind. Pilocarpine induced a significant increase in accommodative power.