Agreement and potential for arithmetic adjustment of anterior segment measurements across IOLMaster 700, Pentacam HR, and Sirius

We aimed to evaluate the absolute agreement, consistency, and the potential of arithmetic adjustment for measurements across a swept-source optical coherence tomography biometer (IOLMaster 700), a single Scheimpflug-based tomographer (Pentacam HR), and a combined Scheimpflug-Placido disc-based tomographer (Sirius). This cross-sectional study analyzed the corneal keratometry parameters (Sim-K1, Sim-K2, and Sim-Km, corneal astigmatism (CA), and its Jackson power vectors (J0 and J45), central corneal thickness (CCT), anterior chamber depth (ACD), and the horizontal white-to-white distance (WTW) of 111 healthy eyes. The inter-device agreement was assessed using the Bland-Altman limits of agreement (LoA) and two types of intraclass correlation coefficient (ICC) analyses. A mean difference (MD) translating to less than 0.25D in refractive outcomes was considered clinically acceptable. Except for the WTW (ICC(2,1) = 0.52, ICC(3,1) = 0.65), the inter-device agreement was excellent for all parameters (ICC(2,1) and ICC(3,1) > 0.90), with the CA and its power vectors (ICC(2,1) and ICC(3,1): 0.87-0.90) being slightly inferior. WTW values varied substantially across devices, but applying a constant adjustment (MD = 0.36) between Pentacam HR and Sirius improved agreement (ICC(2,1) rising from 0.59 to 0.90), whereas adjustment was not feasible with IOLMaster 700. CCT and ACD may be considered interchangeable across the three, particularly in intraocular lens (IOL) power calculation (the widest LoA were - 0.20 to 0.16 mm for ACD and - 10.99 to 25.42 μm for CCT, respectively). Keratometry values exhibited clinically relevant LoA (the widest LoA for Sim-Km: - 0.77 to 0.80 diopters), limiting their direct interchangeability. Although WTW showed the greatest variability (the widest LoA: - 0.86 to 0.64 mm), the agreement between Pentacam HR and Sirius could be improved through an arithmetic adjustment. This adjustment indicated a systematic error rather than random variability between Pentacam HR and Sirius. These findings highlight the potential of arithmetic adjustment of WTW, an important variable in implantable collamer lens sizing, similar to constant optimization in the IOL power formulas.