Purpose: To evaluate the effect of attempted eyelid closure on intraocular pressure measurement.
Methods: Normal subjects underwent intraocular pressure measurement in both eyes using Goldmann applanation tonometry and Tono-pen XL (Mentor, Inc, Norwell, Massachusetts) by the same examiner holding the eyelids open, both with and without the subject simultaneously attempting forced eyelid closure. Subjects were seated during all measurements and waited 5 minutes between measurements with each instrument; the order of measurement was randomized.
Results: Thirty eyes of 15 subjects (six men, nine women) were enrolled. Mean age was 30.5 +/- 5.2 years (range, 24 to 40 years). With Goldmann applanation tonometry, intraocular pressure increased in both eyes with attempted eyelid closure by a mean of 1.5 +/- 2.0 mm Hg (P =.0002, paired t test; range, -2 to 8 mm Hg). With the Tono-pen XL, intraocular pressure also increased in both eyes with attempted eyelid closure by a mean of 1.9 +/- 2.7 mm Hg (P =.0002, paired t test; range, -2 to 9 mm Hg). Tono-pen XL mean intraocular pressure values in both eyes (14.4 +/- 2.3 mm Hg) consistently overestimated those of Goldmann applanation tonometry (13.0 +/- 2.2 mm Hg) by a mean of 1.4 +/- 2.3 mm Hg.
Conclusions: Attempted forced eyelid closure is a common and statistically significant source of error in routine outpatient measurement of intraocular pressure and could influence clinical management of glaucoma.