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Parameter-Dependent Agreement and Proportional Bias Between a Domestically Developed Scheimpflug-Based Imaging System
Wei Cui1,2,3, Kun Liu1,2,3, Fanqin Kong1,2,3
1Eye Institute of Shandong First Medical University, Qingdao Eye Hospital of Shandong First Medical University, Qingdao, People's Republic of China.
Purpose:
Accurate assessment of anterior segment parameters is essential for clinical decision-making and ophthalmic research. With the increasing availability of domestically developed anterior segment imaging systems, independent evaluation of their measurement characteristics relative to established devices is required. This study aimed to compare anterior segment measurements obtained using Scansys TA517, a domestically developed Scheimpflug-based imaging system, with those from Pentacam HR.
Methods:
A total of 214 eyes were examined using both devices during the same visit. Anterior chamber depth (ACD), anterior chamber angle (ACA), anterior chamber volume (ACV), white-to-white corneal diameter (WTW), pupil diameter (PD), and the ACD/WTW ratio were analyzed. Inter-device differences were evaluated using Bland-Altman analysis, and proportional bias was assessed by linear regression of inter-device differences against the mean of the two measurements.
Results:
Inter-device differences varied substantially across parameters. ACD and the ACD/WTW ratio demonstrated minimal mean bias, narrow limits of agreement, and no proportional bias, indicating high inter-device stability and reliability. In contrast, ACA and ACV exhibited larger bias, wider limits of agreement, and significant proportional bias. WTW and PD showed intermediate stability with evidence of magnitude-dependent discrepancies.
Conclusion:
In conclusion, inter-device agreement between Scansys TA517 and Pentacam HR is parameter-dependent. Linear and ratio-based parameters demonstrated greater stability than angle- and volume-based measurements, and proportional bias was present for several parameters. These findings highlight the importance of parameter-specific and device-specific interpretation when comparing anterior segment measurements across imaging systems.
