Biometric Measurement Devices Show Repeatability, May Be Used Interchangeably

Swept source-optical coherence tomography (SS-OCT) and optical low coherence reflectometry (OLCR) are biometric measurement devices that demonstrate good repeatability and may be used interchangeably to obtain ocular biometric parameters, according to research published in Eye and Vision.

Researchers included 74 participants (mean age, 31.0 years; 55 women) without ocular pathologies in the prospective investigation to evaluate the repeatability of the 2 instruments. Study participants underwent flat keratometry (K1), steep keratometry (K2), central corneal thickness, anterior chamber depth, lens thickness, and axial length measurements 3 times with each device. Investigators analyzed the repeatability of each instrument using intrasubject standard deviation, coefficient of variability (CoV), and coefficient of repeatability (CoR), and used Bland-Altman analysis to evaluate the agreement between the 2 biometric measurement devices.

Repeatability was excellent between the 2 instruments, the report shows — CoV values were less than 0.2%, less than 0.4% and less than 0.55% for K1, K2, and CCT, respectively. Higher CoV values ranging from 0.56% to 1.74% were noted for anterior chamber depth and lens thickness measurements. The lowest CoV values were noted for the axial length measurements (0.03% and 0.06% with SS-OCT and OLCR, respectively) and axial length measurements had the highest repeatability determined by both CoV and CoR values. Central corneal thickness measurements were the least repeatable — both this measurement and lens thickness were significantly different between the two biometric measurement devices (P <.001 and P =.018, respectively). Despite attaining statistical significance, the study authors state that these differences were clinically negligible, according to the report.

“Comparing the instruments, we believe that despite the statistically significant differences reported in [central corneal thickness] and [lens thickness] and the [limits of agreement] values, we consider them negligible from a clinical standpoint,” the researchers explain. “Hence, the two biometers can be used interchangeably.”

Study limitations include a strict inclusion of individuals without ocular pathologies and the inclusion of only 2 ocular biometric measurement devices.