OCT- versus Scheimpflug-based Total Corneal Power Measurements Changes in Myopic Astigmatic SMILE Procedures

ABSTRACT

Purpose

To evaluate the value of total keratometry (TK) to estimate corneal power in eyes that underwent SMILE for treatment of myopia or myopic astigmatism in subgroups of low and high astigmatism.

Methods

The difference between preoperative and postoperative measurements of corneal power (ΔTCRP, ΔTK) was compared with the surgically induced refractive change at the corneal plane (ΔSE_co) by Pearson correlation. Vector analysis of TCRP- and TK-derived astigmatism was performed to evaluate the corneal astigmatism. Single-angle plots were generated with the AstigMATIC tool for standard astigmatism vector analysis.

Results

Paired t-test revealed statistically significant differences in preoperative (p = .02) and postoperative (p = .0455) measurements between TK and TCRP in the group of high-level astigmatism and the postoperative low astigmatism group (p < .01). No significant differences were found in preoperative data in the group of low-level astigmatism (p = .60). The correlation of ΔSEco and TK (low astigmatism, R² = 0.978; high astigmatism R² = 0.980) was stronger than the correlation of TCRP 4.0 mm and ΔSEco (low astigmatism, R² = 0.743; high astigmatism R² = 0.959) in both astigmatic groups. The vector analysis demonstrated nearly identical results concerning the correction index (CI) for TK and TCRP. Comparing the difference vector (DV) between both parameters, TK-derived results were closer to the optimum.

Conclusions

The findings endorse TK as a reliable measure of corneal power after SMILE in patients with low and high astigmatism.

KEYWORDS:

• SMILE
• TK
• TCRP
• astigmatism
• corneal power

Disclosure statement

The authors have no proprietary or financial or any other competing interest in any of the materials or equipment mentioned in this study. We declare no public or private financial support for the conduct of this study.

Disclosure

Mehdi Shajari: Consultant for Oculus, Oertli, Santen, Staar and Zeiss.

Daniel Kook: Consultant: Alcon, Zeiss Meditec.

Rainer Wiltfang: Consultant for Carl Zeiss Meditec AG.

Siegfried Priglinger: Alcon, Polytech/Domilens, Örtli, Novartis, Zeiss.

Wolfgang J. Mayer: Consultant or Advisory Board: Zeiss Meditec, Alcon, Ziemer, Polytech/Domilens, Allergan.

Roman Lischke, Nikolaus Feucht and Martin Bechmann have no financial interests.