Tonometry

Tonometry is a diagnostic procedure used to measure the pressure of fluids within the body, particularly in the eyes and blood vessels.

Types of Tonometry

• Applanation Tonometry: This method measures intraocular pressure (IOP) by flattening a small area of the cornea. It is commonly used to diagnose and monitor glaucoma.
• Indentation Tonometry: This technique measures IOP by indenting the cornea with a plunger or a probe.
• Pneumatonometry: This method uses a puff of air to measure IOP, and is often used as a screening tool for glaucoma.
• Rebound Tonometry: This technique measures IOP by using a small probe that makes contact with the cornea and then rebounds, providing a measurement of the pressure.

Procedure

The procedure for tonometry typically involves the following steps:

• The patient is seated in a comfortable position and asked to look straight ahead.
• The eye is numbed with anesthetic drops to minimize discomfort.
• The tonometer is placed against the cornea, either directly or through a plastic tip.
• The measurement is taken, which may involve a brief puff of air or a gentle indentation of the cornea.
• The reading is recorded and compared to normal values to determine if further evaluation is needed.

Indications

Tonometry is commonly used to:

• Diagnose and monitor glaucoma, a condition characterized by increased IOP that can lead to vision loss.
• Evaluate patients with ocular hypertension, which is an increase in IOP without any signs of glaucoma.
• Monitor patients after eye surgery or trauma.

Risks and Complications

While tonometry is generally a safe procedure, there are some potential risks and complications to be aware of:

• Infection: As with any invasive procedure, there is a small risk of infection with tonometry.
• Corneal abrasion: The tonometer may cause a minor scratch on the cornea, which can be uncomfortable but usually heals quickly.
• Allergic reaction: Some patients may experience an allergic reaction to the anesthetic drops used during the procedure.

Interpretation of Results

The results of tonometry are typically interpreted as follows:

• A normal IOP reading is usually between 10-21 mmHg.
• An elevated IOP reading may indicate glaucoma or ocular hypertension, and further evaluation and treatment may be necessary.