CCC.1 Axial Measurements

An axial measurements device is used to take axial measurements of the eye, from the anterior surface of the cornea to either the surface of the retina (ultrasound) or the retinal photoreceptors (optical). The axial measurements are typically expressed in mm (Ophthalmic Axial Length (0022,1010). Currently these measurements are taken using ultrasound or laser light. The measurements are used in calculation of intraocular lens power for cataract surgery. Axial measurements devices and software on other systems perform intraocular lens power calculations using the axial measurements in addition to measurements from other sources (currently by manual data entry, although importation from other software systems is expected in the future).

When the natural lens of the eye turns opaque it is called a cataract. The cataract is surgically removed, and a synthetic intraocular lens is placed where the natural lens was before. The power of the lens that is placed determines what the patient’s refractive error will be, meaning what power his glasses will need to be to maximize vision after surgery.

Axial measurements devices provide graphical displays that help clinicians to determine whether or not the probe used in taking the measurements is aligned properly. Annotations on the display provide information such as location of gates that assists the clinician in assessing measurement quality. High, fairly even waveform spikes suggest that the measurement producing a given graph is likely to be reliable. The quality of the graphical display is one of the factors that a clinician considers when choosing which axial length measurement to use in calculating the correct intraocular lens power for a given patient.