This is a test to measure the shape and size of the eye. It is commonly used to calculate the power of intraocular lens (IOL) implants required for cataract and refractive surgery. Biometry can be performed using either optical coherence interferometry or ultrasound technology.

At the Lakefield Surgical Centre we use the state of the art Zeiss IOL Master 500 (optical coherence interferometry). This equipment is able to measure the length of the eyeball (axial length), curvature of the cornea (keratometry), anterior chamber depth and white to white (corneal width). It uses several different formulas to give the surgeon options as to IOL lens powers for each individual eye

How is it done?

This is a non-invasive test performed by placing your chin on the instrument chin rest and focussing on a target light. It takes only a few minutes to perform.

Ultrasound biometry is used for patients who have dense cataracts where measurements on the IOL Master are not possible. This test involves placing an ultrasound probe on the surface of the cornea to obtain measurements of axial length. These can then be used along with keratometry measurements to calculate IOL lens powers. A local anaesthetic eye drop is inserted into the eye before this test is performed.

Before your appointment:

Whether we use the IOL Master or the ultrasound biometer it is important to remove your contact lenses prior to the measurements being taken. Below is a guide as to how long prior to your appointment your contact lenses should be left out:

• Soft daily disposable contact lenses……………………………24 hours
• Soft two weekly and monthly contact lenses……………48 hours
• Extended wear soft contact lenses…………………………………………1 week
• Rigid gas permeable contact lenses……………………………………2 weeks