Analysis of corneal asphericity (Q value) and its related factors in adult Egyptians: a cross-sectional study

Purpose The aim of this study was to determine the corneal Q value and its related factors in adult Egyptians and to compare the Q value of Egyptians with other ethnic groups. Design This was a cross-sectional study. Patients and methods The study included 500 eyes of 250 Egyptian patients. There were 130 female and 120 male patients, with a mean age of 29.96±9.31 years (range=20–60 years). The corneal mean Q value at 6.0- and 8.0-mm diameter together with Q value from each quadrant (nasal, temporal, superior, and inferior) and two meridians (horizontal and vertical) at 8.0-mm diameter were measured using Pentacam HR. Eyes were stratified by age, sex, and spherical equivalent (SE) refractive error. The mean radius of curvature (Rm) and maximum keratometry reading (K-max) of the anterior corneal surface, corneal thinnest location, and anterior chamber depth were measured. Results The average Q values of the anterior surface were −0.27 (±0.125) and −0.37 (±0.141) at 6.0 and 8.0 mm diameter, respectively. The average Q value of each quadrant (nasal, temporal, inferior, and superior) and horizontal and vertical meridians was −0.55 (±0.245), −0.244 (±0.130), −0.33 (±0.189), −0.35 (±0.27), −0.40 (±0.144), and −0.34 (±0.178) at the 8-mm diameter, respectively. The average Q values of the anterior surface were significantly correlated with age, sex, SE refractive errors, maximum keratometry reading (K-max), mean radius of curvature (front), and anterior chamber depth. There was no significant correlation between the average Q values and corneal thickness at the thinnest location. The adult Egyptian Q values were close to African Americans but different from other ethnic groups. Conclusion There was a significant correlation between Q value and age, sex, refractive error, K-max, mean radius of curvature (Rm), and anterior chamber depth. Corneal Q values of adult Egyptians were different from previous studies involving Europeans, white Americans, and Asian populations and was close to African Americans.