Effect of contact lens removal or displacement on intraocular pressure

We conducted a controlled, prospective study involving 102 healthy volunteers to determine the effects of contact lens removal and contact lens displacement on subsequent intraocular pressure measurements. Intraocular pressure was measured at baseline, immediately after contact lens removal or displacement, and 5 minutes thereafter. The method of lens removal was either sliding displacement (51 eyes) or plucking (51 eyes). Right eyes were used for the test, and left eyes served as controls. Compared with baseline measurements, mean intraocular pressure immediately after plucking the lens was 0.8 mm Hg lower (P less than .01) and after sliding the lens was 0.5 mm Hg higher (P less than .05). Intraocular pressure changes of 4.0 mm Hg or more occurred in eight (15.6%) of 51 eyes in the pluck group vs four (7.8%) of 51 control eyes and in two (3.9%) of 51 eyes in the slide group vs zero of 51 control eyes. Compared with baseline, significant differences (P less than .05) were not found 5 minutes later. Clinicians who wish to minimize the influence of contact lens removal on tonometry readings should wait several minutes after contact lens removal before measuring intraocular pressure.