Applanation tonometry with and without fluorescein

Some investigators have suggested that it is not necessary to be fluorescein when doing applanation tonometry. This is incorrect because, in order to visualize the apex of the tear order to visualize the apex of the tear meniscus which defines the applanated area, the tears must be stained with fluorescein. I found an average pressure of 11.72 +/- 3.20 mm Hg in eyes tested without fluorescein compared with an average pressure of 17.34 +/- 4.07 mm Hg when pressures were immediately remeasured with fluorescein. Failure to use fluorescein during applanation tonometry will result in an under-estimation of approximately 5.62 mm Hg.