Characteristics of posterior corneal astigmatism and aberration in cataract patients with high myopia

Objective

This study was to investigate the characteristics of posterior corneal astigmatism (PCA) and aberration in cataract patients with high myopia.

Methods

A retrospective study was designed.Two hundred and eighty-two eligible eyes of 190 cataract patients were enrolled in Eye and ENT Hospital of Fudan University from September to December, 2014.The eyes were classified into two groups according to axial length (AL): high myopia group with 139 eyes (AL≥26 mm) and control group with 143 eyes (AL was 20 to 25 mm). The mean keratometric mid-radius of curvature (Km), corneal central thickness (CCT), astigmatism and aberrations were measured by the rotating Scheimpflug System (Pentacam), and the AL were measured by the partial coherence interferometry (IOL Master). This study followed the Helsinki declaration, and was approved by the Ethic Committee of Eye and ENT Hospital, Fudan University.Informed consent was signed from each patient.

Results

In high myopia group, the mean PCA was 0.3 D (range 0~0.9 D) and 92.8% eyes had PCA values <0.5 D. The steep corneal meridian was aligned vertically (60°~120°) in 87.1% eyes for the posterior corneal surface.There was no significant difference in PCA between the high myopia group and the control group (P=0.797). Significant positive linear correlations was found between PCA and anterior corneal astigmatism (ACA), PCA and anterior corneal root mean square (RMS), PCA and anterior lower-order RMS, PCA and posterior corneal RMS, PCA and posterior high-order RMS, PCA and posterior lower-order RMS (r=0.235, P=0.005; r=0.217, P=0.010; r=0.229, P=0.007; r=0.395, P=0.000; r=0.243, P=0.004; r=0.384, P=0.000). Compared with total corneal astigmatism (TCA), anterior corneal measurements overestimated with-the-rule astigmatism (WTR) by a mean of (0.27±0.18)D in 65.67% eyes, underestimated against-the-rule astigmatism (ATR) by (0.27±0.18)D in 88.10% eyes and underestimated oblique astigmatism (Obl) by (0.22±0.10)D in 63.33% eyes.Compared with total corneal aberrations, anterior corneal aberrations measurements overestimated by (0.275±0.176)μm in 87.05% eyes, and the anterior corneal astigmatism types had no effect on the result.

Conclusions

In high myopia group, 92.8% eyes had PCA values <0.5 D and the main astigmatism type in posterior corneal surface was ATR.The posterior corneal astigmatism and aberration were needed to consider in choosing intraocular lens (IOL) before cataract surgery.