Comparison of optical biometry versus ultrasound biometry in different axial length groups

The accuracy of optical biometry is higher than ocular ultrasound, but it is expensive and has limitations in patients with dense cataracts. On the other hand, ocular ultrasound biometry is still a frequently used technique in most developing countries due to its lower cost. Therefore, it could be helpful for practitioners to know the interchangeability of optical biometry devices with ultrasound biometry devices. This study is conducted to compare the axial length (AL), anterior chamber depth (ACD), and lens thickness (LT) measured by ocular optical and ultrasound biometers in different AL groups.

This prospective consecutive study was performed on 248 eyes of 248 patients. Ocular optical biometry was performed using IOLMaster 700 (swept-source optical coherence tomography-based optical biometry, Carl Zeiss, Germany), and the contact ultrasound biometry was carried out using the US-4000 Nidek Echoscan (Gamagori, Japan). Based on measured AL, patients were divided into three groups: the short eye (AL ≤22 mm), normal eye (22 < AL <24.5 mm), and long eye (AL ≥24.50 mm).

The agreement of AL between these biometers in all, short, normal, and long eyes was 99.9%, 98.3%, 99.6%, and 99.9%, respectively. The ACD agreement between two devices in all, short, normal, and long eyes was 97.0%, 93.8%, 97.2%, and 96.1%, respectively. Furthermore, the agreement of LT between these biometers in all, short, normal, and long eyes was 74.4%, 89.2%, 66.9%, and 90.7%, respectively. There were a very strong positive correlation in AL (r = 0.999) and ACD (r = 0.947) and a good correlation in LT (r = 0.675) between these devices (all P < 0.001).

AL and ACD measured by the IOLMaster 700 optical biometer can be used interchangeably with the US-4000 ultrasound biometer in different AL groups. However, LT measured by these biometers cannot be used interchangeably.