CORNEAL TOPOGRAPHY AND MYOPIA - A CROSS-SECTIONAL STUDY

Purpose. Central corneal curvature is known to vary with refractive er ror, but the relation between corneal topography and ametropia is less clear. The current study was conducted to determine whether a relatio n exists between corneal asphericity and myopia. Associations between corneal asphericity and each of the components of refraction also were examined. Methods. Corneal asphericity and apical radius of curvature were determined for 113 eyes (spherical equivalent refractive error 0.25 diopter [D] to -9.88 D) by fitting a conicoid equation to videoke ratoscopic data. Computerized videokeratoscopic images were recorded u sing a Topographic Modeling System. Keratometry also was performed on each eye. Anterior chamber depth, lens thickness, vitreous chamber dep th, and axial length were measured with a hand-held biometric ruler. R esults. A low but statistically significant positive correlation was f ound between corneal asphericity (Q) and spherical equivalent refracti ve error (r = 0.275, P < 0.01). Significant relations also were observ ed between Q and vitreous chamber depth (r = 0.17, P < 0.1) and betwee n Q and axial length (r = 0.24, P < 0.05). The association between Q a nd corneal radius of curvature was found not to be significant. Eyes w ith higher levels of myopia had steeper central corneal curvatures, de eper anterior and vitreous chambers, and greater axial lengths. Conclu sions. A tendency for the cornea to flatten less rapidly in the periph ery with increasing myopia was shown. Decreased peripheral corneal fla ttening also was observed in association with increasing vitreous cham ber depth and increasing axial length. These findings have implication s for refractive surgery outcomes, schematic eye modeling, contact len s design, and ocular aberration analysis.