What is an Exophthalmometer Used For?

An exophthalmometer is a medical measuring instrument used to determine the position of the eyeball (the degree of protrusion or recession of the eye) in relation to the orbit.

Applications of an Exophthalmometer

• Assessing and monitoring exophthalmus (proptosis) – protruding eyes, often seen in thyroid-related conditions such as Graves’ disease (orbitopathy).
• Measuring enophthalmus – recessed eyes, for example after trauma or an orbital fracture.
• Comparing both eyes to detect asymmetry.
• Monitoring changes in eye position during treatment or disease progression.

Available Hertel Exophthalmometers

The most commonly used type is the Hertel exophthalmometer; we offer 2 versions:

• The Oculus exophthalmometer
• The Good-Lite Hertel exophthalmometer, which is essentially identical but more affordable.

Both models rest on the bony edges of the orbit and, using a prism, measure the distance from the lateral orbital rim to the anterior surface of the cornea.

Hertel

The Hertel exophthalmometer is a medical instrument designed to measure the position of the eyeball relative to the orbit. It is mainly used to diagnose and monitor exophthalmus (protruding eyes) or enophthalmus (sunken eyes), as commonly observed in thyroid-related eye disorders or after orbital fractures.

The name “Hertel” refers to the German ophthalmologist Dr. Ernst Hertel (1879–1943), who developed and introduced this instrument into ophthalmology. His design has since become the worldwide standard for measuring ocular protrusion and asymmetry between the eyes.