Comparison of Biometric Parameters in Standard and Segmental Optical Biometry

Optical biometry is widely used in ophthalmology for different purposes. The Argos (Alcon, USA) device, which recently entered the Russian market, uses different refractive indices for different eye structures. This feature fundamentally distinguishes it from other models. The issue of its comparability with other biometers in the Russian population has not been researched sufficiently.

Purpose. To compare keratometry in the flat (K1) and steep (K2) meridians, mean keratometry (Km), axial length (AL), anterior chamber depth (ACD), lens thickness (LT), white-to-white (WTW) and the frequency of relevant AL measurement between the Argos and IOLMaster 700 devices.

Patients and methods. Two hundred fifty-one patients (368 eyes) were included in the study regardless of the presence of cataract: 244 females (66.3 %) and 124 males (33.7 %). The mean age was 68.18 ± 13.36 years (24–92 years). The exclusion criteria were: unstable visual fixation, pseudophakia, aphakia, history of vitrectomy, the difference between the dates of biometry on the Argos and IOLMaster 700 more than 1 month. Clinical significance of the differences was assessed using Bland-Altman plots and 95 % limits of agreement (95 % LoA). Results. The frequency of relevant AL measurements was 100 % on the Argos, and 99.2 % on the IOLMaster 700 (p = 0.25). The K1, K2, Km, ACD, LT and WTW measurements were significantly higher on the Argos compared to the IOLMaster 700. AL did not differ significantly only in the range of 22.0–23.0 mm. At AL < 22.0 mm this parameter was significantly higher on the Argos, at AL > 23.0 mm — on the IOLMaster 700. The more was the AL deviation from the range of 22.0–23.0 mm, the greater was the difference in AL between the two biometers. The difference in ACD was inversely proportional to the magnitude of ACD. Strong correlations were found for all studied parameters on the two biometers, however, 95 % LoA were wide.

Conclusion. The differences in keratometry, AL, ACD, LT and WTW between the Argos and IOLMaster 700 are clinically significant and therefore this biometers cannot be considered interchangeable in all clinical situations.

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