Assessing the corneal power change after refractive surgery using Scheimpflug imaging

Area of Science:

• Ophthalmology
• Corneal Surgery
• Refractive Error Correction

Background:

• Small-incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) are common refractive surgeries.
• Accurate prediction of surgically induced refractive change is crucial for successful outcomes.
• The Pentacam HR is an advanced diagnostic tool for corneal analysis.

Purpose of the Study:

• To evaluate the accuracy of the Pentacam HR in predicting refractive changes after SMILE and FS-LASIK.
• To compare different Pentacam HR measurement methods for refractive prediction.

Main Methods:

• Retrospective analysis of 310 myopic eyes (SMILE), 111 myopic eyes (FS-LASIK), and 40 hyperopic astigmatic eyes (FS-LASIK).
• Comparison of manifest refractive change with Pentacam HR's Sagittal Power, True Net Power, and Total Corneal Refractive Power (TCRP).
• Multiple linear regression to identify predictors of prediction error.

Main Results:

• TCRP using a 4.0 mm diameter (Apex, Zone) accurately predicted refractive change across all groups.
• Spherical equivalent prediction errors were low: 0.08 ± 0.41 D (SMILE), 0.05 ± 0.61 D (myopic FS-LASIK), -0.15 ± 0.49 D (hyperopic astigmatism FS-LASIK).
• Preoperative refractive error significantly impacted Pentacam HR prediction accuracy.

Conclusions:

• Ray tracing calculations with Scheimpflug imaging (Pentacam HR) accurately assess refractive changes post-corneal laser surgery.
• TCRP is a reliable metric for predicting surgical outcomes in SMILE and FS-LASIK.
• Understanding the influence of preoperative refractive error can refine surgical planning.