What result can occur from excessive fluorescein instillation during tonometry?

Excessive fluorescein instillation during tonometry can lead to a higher than true intraocular pressure (IOP) reading. This is primarily due to the additional thickness and viscosity that the instilled fluorescein adds to the tear film. When the tonometer applanation prism touches the cornea, the presence of excess fluorescein can create an expanded area of applanation, which alters the pressure readings obtained. Since the tonometry measures the pressure at the point of applanation, an increased volume of fluorescein in the tear film can falsely elevate the recorded IOP, leading the clinician to conclude that the pressure is higher than it actually is. This can potentially mislead the diagnosis and management of conditions such as glaucoma, where accurate IOP measurement is crucial.

In contrast, other outcomes such as corneal abrasion or misalignment of mires are not directly caused by the excessive use of fluorescein and would typically result from other factors or practices in tonometry. Furthermore, lower than true IOP is generally associated with insufficient application of fluorescein, rather than an excessive amount.