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A Comparative Study of Total Corneal Power Using a Ray Tracing Method Obtained from 3 Different Scheimpflug Camera
Chao Pan1, Weina Tan1, Giacomo Savini2
1School of Ophthalmology and Optometry and Eye Hospital, Wenzhou Medical University, Wenzhou, China; Hankou Aier Eye Hospital, Jianghan District, Wuhan, China.
American Journal of Ophthalmology
|April 12, 2020
Summary
Three Scheimpflug tomographers provide similar ray-traced corneal power measurements. After adjustment, these devices show good agreement with automated keratometers and Placido-based topographers for clinical use.
Area of Science:
- Ophthalmology
- Biomedical Optics
- Corneal Imaging
Background:
- Accurate corneal power measurement is crucial for refractive surgery outcomes.
- Scheimpflug tomography offers advanced ray-tracing capabilities for corneal analysis.
- Comparing different Scheimpflug devices and established methods is essential for clinical validation.
Purpose of the Study:
- To assess the agreement of ray-traced corneal power values from three Scheimpflug tomographers.
- To determine arithmetic adjustment factors for these devices.
- To compare their performance against an automated keratometer (IOLMaster) and a Placido-based topographer (Allegro Topolyzer).
Main Methods:
- Prospective reliability analysis involving 74 eyes of healthy subjects.
- Corneal power measurements using Pentacam, Sirius, Galilei (Scheimpflug), IOLMaster (keratometer), and Allegro Topolyzer (Placido).
- Analysis of total corneal refractive power (TCRP), mean pupil power (MPP), total corneal power (TCP), mean keratometry (Km), and simulated keratometry (SimK) using ANOVA and Bland-Altman plots.
Main Results:
- TCRP and MPP values showed no significant difference among the Scheimpflug devices (P=0.81).
- TCP values were slightly significantly higher (P<0.001) compared to other ray-traced metrics.
- After arithmetic adjustment, all three Scheimpflug tomographers demonstrated comparable 95% limits of agreement with Km and SimK, ranging from approximately ±0.34 D to ±0.51 D.
Conclusions:
- Ray-traced corneal power values from the three Scheimpflug tomographers are similar and interchangeable in clinical practice.
- These devices achieve satisfactory agreement with conventional automated keratometers and Placido-based topographers post-adjustment.
- The findings support the clinical utility of these Scheimpflug tomographers for corneal power assessment.
