Certified Ophthalmic Assistant Practice Exam

Which type of tonometer is mounted on a slit lamp?

1. Applanation

2. Non-contact

3. Indentation

4. Tonopen

The correct answer is: Applanation

A tonometer that is mounted on a slit lamp is specifically designed for applanation tonometry. This method involves flattening a small area of the cornea, allowing the measurement of intraocular pressure (IOP) based on the force required to achieve that flattening. In a clinical setting, this is often accomplished using a tonometer that is integrated with the slit lamp, providing the practitioner with a stable and magnified view of the eye while taking the measurement. Applanation tonometry is considered the gold standard for measuring IOP due to its reliability and precision. The instrument typically consists of a small probe that contacts the cornea, and the measurement is largely independent of the corneal curvature, which makes it exceptionally accurate. Other types of tonometers mentioned are designed for different methods of measuring eye pressure. Non-contact tonometers use a puff of air to measure IOP without direct contact with the eye, while indentation tonometers measure IOP through the deformation of the cornea using weight. The Tonopen is a portable version used in various settings but is not mounted on a slit lamp, further highlighting the distinction in how these methods operate compared to applanation tonometry mounted on the slit lamp.