Which tonometry technique displaces a minimal amount of fluid?

Which tonometry technique displaces a minimal amount of fluid?

• A. Indentation
• B. Applanation
• C. Elevation
• D. Fixation

Answer: (B)

Flattening a small area of the cornea with a precise, minimal force is the principle behind this method. By applanating the cornea, a tiny patch is kept in a flat, neutral state rather than pushed inward or manipulated in a way that disturbs the eye’s internal fluids. This small, controlled deformation means the aqueous humor isn’t displaced appreciably, so the force required to flatten that patch corresponds to the intraocular pressure with less distortion from fluid movement. In contrast, indentation tonometry presses into the cornea, distorting the globe more and moving a greater volume of aqueous humor, which can alter the reading. Other methods involve different interactions with the cornea that don’t achieve the same minimal displacement, making applanation the best choice when the goal is to minimize fluid movement.

Flattening a small area of the cornea with a precise, minimal force is the principle behind this method. By applanating the cornea, a tiny patch is kept in a flat, neutral state rather than pushed inward or manipulated in a way that disturbs the eye’s internal fluids. This small, controlled deformation means the aqueous humor isn’t displaced appreciably, so the force required to flatten that patch corresponds to the intraocular pressure with less distortion from fluid movement.

In contrast, indentation tonometry presses into the cornea, distorting the globe more and moving a greater volume of aqueous humor, which can alter the reading. Other methods involve different interactions with the cornea that don’t achieve the same minimal displacement, making applanation the best choice when the goal is to minimize fluid movement.