Excessive fluorescein during Goldmann applanation tonometry leads to what result?

When excessive fluorescein is used during Goldmann applanation tonometry, it can lead to a measured intraocular pressure that is higher than the true pressure. This occurs because the increased thickness of the fluorescein layer creates a greater surface tension effect on the cornea when the tonometer prism is applied. The increased thickness interferes with the accurate reading, as it alters the behavior of the corneal surface under the prism, leading to an overestimation of the intraocular pressure.

Essentially, the Goldmann tonometer measures the pressure based on the applanation of the cornea. If the thickness of the fluorescein layer is too great, the force necessary to flatten the cornea (which is how pressure is determined) will be artificially increased, thus resulting in a reading that suggests a higher pressure than is actually present in the eye. This is an important consideration for practitioners, as it emphasizes the need to use an appropriate amount of fluorescein for accurate tonometry results.