A Modified Formula for Intraocular Lens Power Calculation Based on Aphakic Refraction in a Pediatric Population

Area of Science:

• Ophthalmology
• Pediatric Ophthalmology
• Refractive Surgery

Background:

• Accurate intraocular lens (IOL) power calculation is essential for visual outcomes in pediatric aphakia.
• Aphakic refraction (AR) techniques are used for secondary IOL power calculation when initial biometry is unavailable or inaccurate.
• Existing AR formulas may lead to refractive errors in pediatric populations.

Purpose of the Study:

• To investigate and optimize the accuracy of aphakic refraction (AR) techniques for secondary intraocular lens (IOL) power calculation in pediatric aphakic eyes.
• To compare the performance of standard AR formulas with a modified formula and biometric measurements.

Main Methods:

• Thirty-three aphakic eyes of 18 children underwent secondary IOL implantation.
• Axial length (AL) was measured using optical biometry for standard formulas (SRK-T, Holladay II, Hoffer-Q).
• Aphakic refraction (AR) and spherical equivalent (SE) were used in Ianchulev and Leccissotti formulas; a modified formula was also evaluated. True IOL power was determined by postoperative SE at 3 months.

Main Results:

• Standard AR formulas (Ianchulev, Leccissotti) resulted in significant myopic surprise, with median absolute errors (MedAE) of 4.4 D and 7.3 D, respectively.
• Biometric formulas achieved a MedAE of 0.8 D.
• The modified AR formula demonstrated a reduced MedAE of 0.5 D, comparable to biometric formulas (P=0.22), and minimized myopic surprise.

Conclusions:

• Standard AR formulas (Ianchulev, Leccissotti) are inaccurate for secondary IOL power calculation in pediatric aphakia, causing significant myopic surprise.
• A modified AR formula provides more accurate SE prediction, comparable to established biometric methods.
• The modified formula offers a valuable tool for optimizing IOL power calculations in pediatric aphakic eyes.