Comparative study on the measurements of biological parameters of anterior segment by two anterior segment analyzers: Scansys and Pentacam
Liu Yin, Jiang Wenshan
2023, 32(6):
502-508.
doi:10.13281/j.cnki.issn.1004-4469.2023.06.010
Asbtract
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526 )
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Objective To evaluate the difference and consistency of biological parameters of anterior segment measured by two anterior segment analyzers: Scansys and Pentacam. Design Consistency evaluation study. Participants Randomly select 158 initial visit patients (158 eyes) who received myopia surgery at General Hospital of Central Theater Command in August 2022. The comparison will be based on the right eye. Methods The anterior segment biometric parameters were measured using both Scansys and Pentacam anterior segment analyzers by the same physician. The differences and agreements in the anterior segment biometric parameters were evaluated using the Bland-Altman method, while the comparison of corneal astigmatism (CA) was performed using vector analysis. Main Outcome Measures Parameters of anterior segment, including K1, K2, Km, Rm, CA, central corneal thickness (CCT), anterior chamber depth (ACD), corneal diameter (WTW), pupil diameter (PD), anterior chamber volume (ACV), anterior chamber angle (ACA). Results Compared to Pentacam, Scansys measured smaller values for K1, K2, Km, CCT, ACD, WTW, and ACV, while Rm, PD, and ACA were larger. The differences between the two instruments in measuring K1, K2, Km, Rm, CCT, ACD, WTW, PD, ACV, and ACA were (-0.12±0.19)D, (-0.15±0.20)D, (-0.13±0.16)D, (0.03±0.03)mm, (-17±7.0)μm, (-0.04±0.18)mm, (-0.36±0.14)mm, (0.36±0.45)mm, (-21±20)mm3, and (3.5±4.8)°, respectively. The 95% limits of agreement (95% LoA) were (-0.48~0.25)D , (-0.54~0.24) D, (-0.45~0.18) D, (-0.03~0.08)mm, (-31~-3.5)μm, (-0.38~0.30)mm, (-0.64~-0.08)mm, (-0.52~1.2)mm, (-61~19)mm3, and (-6~13)°, with 94.3%, 95.6%, 95.6%, 93.0%, 98.1%, 94.9%, 96.2%, 96.2%, 95.6% and 98.1% of the data falling within the confidence intervals. There were some differences in CA measurements between the two instruments, with a 95% LoA ranging from -0.51~0.44 D, and the Bland-Altman plot showing that 94.9% of the data fell within the confidence interval. The vector analysis results showed that on the anterior corneal surface, the horizontal and vertical astigmatism values measured by Pentacam were approximately 0.04 D higher than those measured by Scansys, while the 45° axis astigmatism value measured by Pentacam was approximately 0.10 D lower than that measured by Scansys. The total refractive power measured by Pentacam was approximately 0.30 D higher than that measured by Scansys. Conclusion Scansys has a good consistency with Pentacam on the measurement of K2, Km, CCT, WTW, PD, ACV and ACA. However, in the measurement of K1, Rm, ACD and CA, there are significantly differences between Scansys and Pentacam, which should be comprehensively analyzed combined with more examination results in the application of different refractive surgeries. (Ophthalmol CHN, 2023, 32: 502-508)