What color is the light filter used in applanation tonometry?

The light filter used in applanation tonometry is blue. This is significant because the blue filter enhances the visibility of the fluorescein dye that is often used in conjunction with this method. Applanation tonometry measures intraocular pressure by flattening a small area of the cornea, and the blue light allows for better contrast and clarity in observing the fluorescein, which highlights the area being measured. This clarity is crucial for ensuring accurate measurement and diagnosis.

Other colors may not provide the same level of visibility and contrast needed for precise readings during the tonometry process. Therefore, the use of a blue filter plays a critical role in the effectiveness of applanation tonometry.