Measuring corneal thickness is an important part of assessing the health of an eye. This procedure is more technically known as pachymetry. It can help to identify and monitor eye diseases including glaucoma and keratoconus which may cause permanent vision loss or even blindness.

The standard method of pachymetry uses ultrasound. With this technique, a small re-useable ultrasound probe is touched to the centre of the cornea and measurements are taken within a few seconds. This technique has been around for many years and is regarded an accurate and safe procedure.

Downsides of ultrasound pachymetry include that it requires anaesthetic eyedrops for the patient and careful sterilisation of the ultrasound probe between uses.

The UNSW Optometry Clinic has access to two new devices (Nidek Tonoref III and Nidek RS-3000) that can measure corneal thickness by assessing how infrared light reflects from the front and back surfaces of the corneas. These devices could have advantages in that they don’t require any eyedrops, do not have any contact with the eye and may be slightly faster to use than ultrasound pachymetry.

Before using these new devices in practice, we wanted to compare how consistent their results are with ultrasound pachymetry.

We found that the two new devices were easy to use and gave very consistent results. However, both new devices did tend to read slightly lower than ultrasound pachymetry. This difference may be too great for some clinicians to be comfortable with.

Our research suggests that these new devices may be suitable for measuring corneal thickness in patients with low risk of eye disease. Our research also provides some extra data on the internal consistency of ultrasound pachymetry devices.


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Thomas Desmond, BOptom(Hons)/BSc

Patricia Arthur, PhD, BOptom, BMus, GradCertBusMan

Kathleen Watt, BOptom(Hons)