Corneal Asphericity and Its Related Factors in 1052 Chinese Subjects

Purpose. To observe and analyze corneal asphericity and its related factors in Chinese subjects. Methods. The corneal asphericity of 1052 right eyes from a Chinese population was determined using the Wavelight-ALLEGRO Topographer. The corneal asphericity coefficient Q describes the rate of curvature variation of the cornea from its center to the periphery and specifies the type of conicoid that best represents its shape. All cases were grouped by age in years (A: <= 9; B: 10 to 19; C: 20 to 29; D: 30 to 39; E: 40 to 49; F: >= 50), and 223 myopic cases were grouped by magnitude in spherical equivalent (SE) refractive error (low myopia, >-3.0 diopters (D); moderate myopia, -6.0 D < SE <=-3.0 D; high myopia, -8.0 D < SE <=-6.0 D; and super high myopia, SE <=-8.0 D). In addition, corneal asphericity was analyzed by corneal quadrant (nasal, temporal, superior, and inferior) and two meridians (vertical and horizontal). Results. The mean Q value of 1052 right eyes was -0.30 +/- 0.12. Although statistical differences were found between some age groups, no statistical correlation between Q values and age was found in this study (r = -0.58, p = 0.06). Q values of the nasal and superior corneal quadrant were significantly more oblate than that of the temporal and inferior quadrants, respectively (both p < 0.0001). A trend toward more oblate Q values was found as the level of myopia increased (r = 0.166, p = 0.013). There was a negative relationship between Q value and central corneal radius in this entire study population (r = -0.09, p = 0.004). Conclusions. Corneal asphericity in this population is related more to corneal quadrant location than to age. The results from this study suggest that degree of myopia and central corneal radius both have a significant though weak association with corneal asphericity in Chinese eyes. (Optom Vis Sci 2011; 88: 1232-1239)