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A comparison of two methods to calculate axial length
David L Cooke1, Timothy L Cooke2
1Great Lakes Eye Care, Saint Joseph, Michigan, USA; Department of Neurology and Ophthalmology, Michigan State University, College of Osteopathic Medicine, East Lansing, Michigan, USA.
Journal of Cataract and Refractive Surgery
|March 11, 2019
Summary
The ARGOS biometer's sum-of-segments axial length (AL) calculation improved prediction accuracy for most formulas, especially those based on ultrasound data. OKULIX formula using sum-of-segments AL demonstrated the best overall performance in predicting refractive outcomes.
Area of Science:
- Ophthalmic biometry and refractive error prediction.
- Intraocular lens (IOL) power calculation accuracy.
Background:
- Accurate axial length (AL) measurement is crucial for refractive outcomes after cataract surgery.
- Different biometry devices employ distinct AL calculation methods, potentially impacting prediction accuracy.
- The impact of the sum-of-segments AL method versus traditional AL on refractive prediction requires evaluation.
Purpose of the Study:
- To compare the prediction accuracy of the traditional axial length (AL) calculation method from the Lenstar biometer with the sum-of-segments AL method from the ARGOS biometer.
- To evaluate the performance of various established formulas using both AL calculation methods across different eye lengths.
Main Methods:
- A comparative case series involving 1442 eyes from 1070 patients was conducted.
- Nine intraocular lens (IOL) power calculation formulas were assessed, grouped by their origin (ultrasound or optical biometry).
- Formulas were ranked based on Mean Absolute Error (MAE) using both traditional AL and sum-of-segments AL, stratified for short, long, and all eyes.
Main Results:
- The OKULIX formula, utilizing sum-of-segments AL, achieved the best ranking for short eyes and overall.
- The Haigis formula with sum-of-segments AL was the top performer for long eyes.
- While sum-of-segments AL improved predictions for formulas derived from ultrasound data, it negatively impacted the Barrett and Olsen formulas.
Conclusions:
- The method of AL calculation significantly influences refractive prediction accuracy, with the sum-of-segments AL method showing general improvement, particularly for ultrasound-based formulas.
- The OKULIX formula demonstrated superior performance when using the sum-of-segments AL calculation method.
- Formula accuracy is dependent on the specific biometer's internal AL calculation method, highlighting the need for formula selection based on the biometer used.
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