CALCULATED VERSUS A-SCAN RESULT FOR AXIAL LENGTH USING DIFFERENT TYPES OF ULTRASOUND PROBE TIP

The axial lengths of 30 pseudophakic eyes were determined by calculation using geometric optics and by A Scan ultrasound using focused fluid filled 'soft' and solid probes. The results from the same ultrasound machine using both types of probe were analysed for their correlation with the calculated axial lengths. The majority of the ultrasound results were shorter than their calculated values but those obtained with the fluid filled 'soft' probe (with consequently less corneal indentation and axial length shortening) were significantly more accurate than those from the solid probe (0.02 > p > 0.01).