Zeiss IOL Master Biometer

ACD Measurements

White-to-White Measurements

Custom A-Constants

Ocular Biometry is carried out in order to take measurements of the structure inside the eye. We are able to measure the distance from the front of the eye to the surface of the retina and also the thickness of the lens inside the eye. These measurements are often used by surgeons in order to improve the function of the eye after surgery. For example, during a cataract operation, the cloudy lens of the eye is replaced by a clear plastic implant. Biometry measurements are used in order to calculate the power of the replacement lens required to give the best unaided vision afterwards. The measurements are also used by surgeons carrying out corrective surgery on the front of the eye.

Optical Biometry (IOL Master)

The Zeiss IOL Master combines axial length, corneal curvature and anterior chamber depth examination in a single machine. Measurements are taken along the visual axis to ensure the greatest accuracy, measuring to the nearest 0.01mm. Unlike ultrasound biometry, the machine makes no contact with the eye and reduces variability between operators. Internal processing by the machine checks the quality of each measurement and indicates unreliable data. All lens data and measurements are stored on the machine for easy recall. The lens database allows each consultant up to 4 lens constants to be used in the calculations.


Contact lenses should not be worn for at least two weeks before the measurement (or as directed by your consultant). If possible, wear glasses to the appointment instead.

How Long Does This Take?

A typical set of scans may take about 5-10 minutes. This may take longer under some circumstances.