Intraocular lens calculation adjustment after laser refractive surgery using Scheimpflug imaging

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Refractive Surgery

Background:

• Accurate intraocular lens (IOL) power calculation is crucial for successful cataract surgery.
• Corneal refractive surgery significantly alters corneal metrics, complicating standard IOL calculations.
• Existing methods often rely on historical data, which is unavailable for post-refractive surgery eyes.

Purpose of the Study:

• To evaluate a novel IOL calculation method (SToP calculator) utilizing Scheimpflug imaging and partial coherence interferometry (PCI).
• To determine if this method can accurately calculate IOL power without requiring pre-operative refractive surgery data.
• To validate the efficacy of the SToP calculator in eyes that have undergone prior corneal refractive surgery.

Main Methods:

• Retrospective analysis of patient data including Scheimpflug imaging and refractive history.
• Calculation of target refraction using PCI with Holladay 1 and SRK/T formulas.
• Regression analysis to identify factors influencing refractive prediction, specifically the ratio of posterior-to-anterior corneal radius and axial length (AL).

Main Results:

• Regression analysis identified the ratio of corneal radii and AL as key factors affecting target refraction accuracy with the Holladay 1 formula.
• The ratio of corneal radii was significant for the SRK/T formula.
• A new IOL adjustment calculator was developed and validated at a separate center, demonstrating improved accuracy.

Conclusions:

• The ratio of posterior-to-anterior corneal radius is a critical factor in IOL calculation errors post-laser refractive surgery.
• The proposed formula, integrating Scheimpflug data, enhances postoperative refractive outcomes for cataract surgery patients with a history of corneal laser procedures.