Effect of intraocular pressure and central corneal thickness on corneal spherical aberration and asphericity in mild and moderate myopes

Abstract

Objective To investigate the correlation between intraocular pressure (IOP) and central corneal thickness (CCT) and corneal spherical aberration as well as asphericity.Methods This was a cross-sectional study.Two hundred and sixteen eyes in 108 mild-to-moderate myopia patients were examined with the Pentacam HR anterior segment tomographer.The aspheric coefficient (Q value) and corneal spherical aberration results from the different quadrants in both the anterior and posterior corneas (including superior,inferior,nasal,temporal,horizontal and vertical directions)and the data 6,7,8 and 9 mm eccentric diameters were obtained.IOP and CCT were measured by a non-contact tonometer and A-scan ultrasonic corneal pachymeter,respectively.Patients were divided into 2 groups based on the degree of myopia.The relationship between the IOP with and without CCT and corneal spherical aberration as well as asphericity were analyzed.Data was processed using a Pearson correlation analysis,independent samples t test and one-way ANOVA.Results IOP was significantly correlated with anterior corneal asphericity (r=-0.30,P＜0.05 for right eyes; r=-0.34,P＜0.05 for left eyes),but was not significantly correlated with anterior corneal spherical aberration in the mild myopia group.In the moderate myopia group,although IOP was significantly correlated with anterior corneal spherical aberration (r=0.31,P＜0.05 for right eye; r=0.37,P＜0.01 for left eye),there was no significant correlation with anterior corneal Q value.CCT was only significantly correlated with the temporal corneal Q value (r=0.47,P＜0.01 for right eyes; r=0.29,P＜0.05 for left eyes).Conclusion IOP induced a decrease in anterior corneal asphericity in mild myopes,however,it was positively correlated with anterior corneal spherical aberration.The reason for the difference may be related to the compensation mechanism of the cornea itself. Key words: Intraocular pressure; Central corneal thickness; Spherical aberration; Asphericity; Q value; Myopia